diff options
Diffstat (limited to 'drivers/lguest/lguest.c')
| -rw-r--r-- | drivers/lguest/lguest.c | 1108 |
1 files changed, 0 insertions, 1108 deletions
diff --git a/drivers/lguest/lguest.c b/drivers/lguest/lguest.c deleted file mode 100644 index 3ba337dde857..000000000000 --- a/drivers/lguest/lguest.c +++ /dev/null @@ -1,1108 +0,0 @@ -/*P:010 - * A hypervisor allows multiple Operating Systems to run on a single machine. - * To quote David Wheeler: "Any problem in computer science can be solved with - * another layer of indirection." - * - * We keep things simple in two ways. First, we start with a normal Linux - * kernel and insert a module (lg.ko) which allows us to run other Linux - * kernels the same way we'd run processes. We call the first kernel the Host, - * and the others the Guests. The program which sets up and configures Guests - * (such as the example in Documentation/lguest/lguest.c) is called the - * Launcher. - * - * Secondly, we only run specially modified Guests, not normal kernels. When - * you set CONFIG_LGUEST to 'y' or 'm', this automatically sets - * CONFIG_LGUEST_GUEST=y, which compiles this file into the kernel so it knows - * how to be a Guest. This means that you can use the same kernel you boot - * normally (ie. as a Host) as a Guest. - * - * These Guests know that they cannot do privileged operations, such as disable - * interrupts, and that they have to ask the Host to do such things explicitly. - * This file consists of all the replacements for such low-level native - * hardware operations: these special Guest versions call the Host. - * - * So how does the kernel know it's a Guest? The Guest starts at a special - * entry point marked with a magic string, which sets up a few things then - * calls here. We replace the native functions various "paravirt" structures - * with our Guest versions, then boot like normal. :*/ - -/* - * Copyright (C) 2006, Rusty Russell <rusty@rustcorp.com.au> IBM Corporation. - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, but - * WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or - * NON INFRINGEMENT. See the GNU General Public License for more - * details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, write to the Free Software - * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. - */ -#include <linux/kernel.h> -#include <linux/start_kernel.h> -#include <linux/string.h> -#include <linux/console.h> -#include <linux/screen_info.h> -#include <linux/irq.h> -#include <linux/interrupt.h> -#include <linux/clocksource.h> -#include <linux/clockchips.h> -#include <linux/lguest.h> -#include <linux/lguest_launcher.h> -#include <linux/lguest_bus.h> -#include <asm/paravirt.h> -#include <asm/param.h> -#include <asm/page.h> -#include <asm/pgtable.h> -#include <asm/desc.h> -#include <asm/setup.h> -#include <asm/e820.h> -#include <asm/mce.h> -#include <asm/io.h> - -/*G:010 Welcome to the Guest! - * - * The Guest in our tale is a simple creature: identical to the Host but - * behaving in simplified but equivalent ways. In particular, the Guest is the - * same kernel as the Host (or at least, built from the same source code). :*/ - -/* Declarations for definitions in lguest_guest.S */ -extern char lguest_noirq_start[], lguest_noirq_end[]; -extern const char lgstart_cli[], lgend_cli[]; -extern const char lgstart_sti[], lgend_sti[]; -extern const char lgstart_popf[], lgend_popf[]; -extern const char lgstart_pushf[], lgend_pushf[]; -extern const char lgstart_iret[], lgend_iret[]; -extern void lguest_iret(void); - -struct lguest_data lguest_data = { - .hcall_status = { [0 ... LHCALL_RING_SIZE-1] = 0xFF }, - .noirq_start = (u32)lguest_noirq_start, - .noirq_end = (u32)lguest_noirq_end, - .blocked_interrupts = { 1 }, /* Block timer interrupts */ -}; -struct lguest_device_desc *lguest_devices; -static cycle_t clock_base; - -/*G:035 Notice the lazy_hcall() above, rather than hcall(). This is our first - * real optimization trick! - * - * When lazy_mode is set, it means we're allowed to defer all hypercalls and do - * them as a batch when lazy_mode is eventually turned off. Because hypercalls - * are reasonably expensive, batching them up makes sense. For example, a - * large mmap might update dozens of page table entries: that code calls - * paravirt_enter_lazy_mmu(), does the dozen updates, then calls - * lguest_leave_lazy_mode(). - * - * So, when we're in lazy mode, we call async_hypercall() to store the call for - * future processing. When lazy mode is turned off we issue a hypercall to - * flush the stored calls. - */ -static void lguest_leave_lazy_mode(void) -{ - paravirt_leave_lazy(paravirt_get_lazy_mode()); - hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0); -} - -static void lazy_hcall(unsigned long call, - unsigned long arg1, - unsigned long arg2, - unsigned long arg3) -{ - if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) - hcall(call, arg1, arg2, arg3); - else - async_hcall(call, arg1, arg2, arg3); -} - -/* async_hcall() is pretty simple: I'm quite proud of it really. We have a - * ring buffer of stored hypercalls which the Host will run though next time we - * do a normal hypercall. Each entry in the ring has 4 slots for the hypercall - * arguments, and a "hcall_status" word which is 0 if the call is ready to go, - * and 255 once the Host has finished with it. - * - * If we come around to a slot which hasn't been finished, then the table is - * full and we just make the hypercall directly. This has the nice side - * effect of causing the Host to run all the stored calls in the ring buffer - * which empties it for next time! */ -void async_hcall(unsigned long call, - unsigned long arg1, unsigned long arg2, unsigned long arg3) -{ - /* Note: This code assumes we're uniprocessor. */ - static unsigned int next_call; - unsigned long flags; - - /* Disable interrupts if not already disabled: we don't want an - * interrupt handler making a hypercall while we're already doing - * one! */ - local_irq_save(flags); - if (lguest_data.hcall_status[next_call] != 0xFF) { - /* Table full, so do normal hcall which will flush table. */ - hcall(call, arg1, arg2, arg3); - } else { - lguest_data.hcalls[next_call].eax = call; - lguest_data.hcalls[next_call].edx = arg1; - lguest_data.hcalls[next_call].ebx = arg2; - lguest_data.hcalls[next_call].ecx = arg3; - /* Arguments must all be written before we mark it to go */ - wmb(); - lguest_data.hcall_status[next_call] = 0; - if (++next_call == LHCALL_RING_SIZE) - next_call = 0; - } - local_irq_restore(flags); -} -/*:*/ - -/* Wrappers for the SEND_DMA and BIND_DMA hypercalls. This is mainly because - * Jeff Garzik complained that __pa() should never appear in drivers, and this - * helps remove most of them. But also, it wraps some ugliness. */ -void lguest_send_dma(unsigned long key, struct lguest_dma *dma) -{ - /* The hcall might not write this if something goes wrong */ - dma->used_len = 0; - hcall(LHCALL_SEND_DMA, key, __pa(dma), 0); -} - -int lguest_bind_dma(unsigned long key, struct lguest_dma *dmas, - unsigned int num, u8 irq) -{ - /* This is the only hypercall which actually wants 5 arguments, and we - * only support 4. Fortunately the interrupt number is always less - * than 256, so we can pack it with the number of dmas in the final - * argument. */ - if (!hcall(LHCALL_BIND_DMA, key, __pa(dmas), (num << 8) | irq)) - return -ENOMEM; - return 0; -} - -/* Unbinding is the same hypercall as binding, but with 0 num & irq. */ -void lguest_unbind_dma(unsigned long key, struct lguest_dma *dmas) -{ - hcall(LHCALL_BIND_DMA, key, __pa(dmas), 0); -} - -/* For guests, device memory can be used as normal memory, so we cast away the - * __iomem to quieten sparse. */ -void *lguest_map(unsigned long phys_addr, unsigned long pages) -{ - return (__force void *)ioremap(phys_addr, PAGE_SIZE*pages); -} - -void lguest_unmap(void *addr) -{ - iounmap((__force void __iomem *)addr); -} - -/*G:033 - * Here are our first native-instruction replacements: four functions for - * interrupt control. - * - * The simplest way of implementing these would be to have "turn interrupts - * off" and "turn interrupts on" hypercalls. Unfortunately, this is too slow: - * these are by far the most commonly called functions of those we override. - * - * So instead we keep an "irq_enabled" field inside our "struct lguest_data", - * which the Guest can update with a single instruction. The Host knows to - * check there when it wants to deliver an interrupt. - */ - -/* save_flags() is expected to return the processor state (ie. "eflags"). The - * eflags word contains all kind of stuff, but in practice Linux only cares - * about the interrupt flag. Our "save_flags()" just returns that. */ -static unsigned long save_fl(void) -{ - return lguest_data.irq_enabled; -} - -/* "restore_flags" just sets the flags back to the value given. */ -static void restore_fl(unsigned long flags) -{ - lguest_data.irq_enabled = flags; -} - -/* Interrupts go off... */ -static void irq_disable(void) -{ - lguest_data.irq_enabled = 0; -} - -/* Interrupts go on... */ -static void irq_enable(void) -{ - lguest_data.irq_enabled = X86_EFLAGS_IF; -} -/*:*/ -/*M:003 Note that we don't check for outstanding interrupts when we re-enable - * them (or when we unmask an interrupt). This seems to work for the moment, - * since interrupts are rare and we'll just get the interrupt on the next timer - * tick, but when we turn on CONFIG_NO_HZ, we should revisit this. One way - * would be to put the "irq_enabled" field in a page by itself, and have the - * Host write-protect it when an interrupt comes in when irqs are disabled. - * There will then be a page fault as soon as interrupts are re-enabled. :*/ - -/*G:034 - * The Interrupt Descriptor Table (IDT). - * - * The IDT tells the processor what to do when an interrupt comes in. Each - * entry in the table is a 64-bit descriptor: this holds the privilege level, - * address of the handler, and... well, who cares? The Guest just asks the - * Host to make the change anyway, because the Host controls the real IDT. - */ -static void lguest_write_idt_entry(struct desc_struct *dt, - int entrynum, u32 low, u32 high) -{ - /* Keep the local copy up to date. */ - write_dt_entry(dt, entrynum, low, high); - /* Tell Host about this new entry. */ - hcall(LHCALL_LOAD_IDT_ENTRY, entrynum, low, high); -} - -/* Changing to a different IDT is very rare: we keep the IDT up-to-date every - * time it is written, so we can simply loop through all entries and tell the - * Host about them. */ -static void lguest_load_idt(const struct Xgt_desc_struct *desc) -{ - unsigned int i; - struct desc_struct *idt = (void *)desc->address; - - for (i = 0; i < (desc->size+1)/8; i++) - hcall(LHCALL_LOAD_IDT_ENTRY, i, idt[i].a, idt[i].b); -} - -/* - * The Global Descriptor Table. - * - * The Intel architecture defines another table, called the Global Descriptor - * Table (GDT). You tell the CPU where it is (and its size) using the "lgdt" - * instruction, and then several other instructions refer to entries in the - * table. There are three entries which the Switcher needs, so the Host simply - * controls the entire thing and the Guest asks it to make changes using the - * LOAD_GDT hypercall. - * - * This is the opposite of the IDT code where we have a LOAD_IDT_ENTRY - * hypercall and use that repeatedly to load a new IDT. I don't think it - * really matters, but wouldn't it be nice if they were the same? - */ -static void lguest_load_gdt(const struct Xgt_desc_struct *desc) -{ - BUG_ON((desc->size+1)/8 != GDT_ENTRIES); - hcall(LHCALL_LOAD_GDT, __pa(desc->address), GDT_ENTRIES, 0); -} - -/* For a single GDT entry which changes, we do the lazy thing: alter our GDT, - * then tell the Host to reload the entire thing. This operation is so rare - * that this naive implementation is reasonable. */ -static void lguest_write_gdt_entry(struct desc_struct *dt, - int entrynum, u32 low, u32 high) -{ - write_dt_entry(dt, entrynum, low, high); - hcall(LHCALL_LOAD_GDT, __pa(dt), GDT_ENTRIES, 0); -} - -/* OK, I lied. There are three "thread local storage" GDT entries which change - * on every context switch (these three entries are how glibc implements - * __thread variables). So we have a hypercall specifically for this case. */ -static void lguest_load_tls(struct thread_struct *t, unsigned int cpu) -{ - /* There's one problem which normal hardware doesn't have: the Host - * can't handle us removing entries we're currently using. So we clear - * the GS register here: if it's needed it'll be reloaded anyway. */ - loadsegment(gs, 0); - lazy_hcall(LHCALL_LOAD_TLS, __pa(&t->tls_array), cpu, 0); -} - -/*G:038 That's enough excitement for now, back to ploughing through each of - * the different pv_ops structures (we're about 1/3 of the way through). - * - * This is the Local Descriptor Table, another weird Intel thingy. Linux only - * uses this for some strange applications like Wine. We don't do anything - * here, so they'll get an informative and friendly Segmentation Fault. */ -static void lguest_set_ldt(const void *addr, unsigned entries) -{ -} - -/* This loads a GDT entry into the "Task Register": that entry points to a - * structure called the Task State Segment. Some comments scattered though the - * kernel code indicate that this used for task switching in ages past, along - * with blood sacrifice and astrology. - * - * Now there's nothing interesting in here that we don't get told elsewhere. - * But the native version uses the "ltr" instruction, which makes the Host - * complain to the Guest about a Segmentation Fault and it'll oops. So we - * override the native version with a do-nothing version. */ -static void lguest_load_tr_desc(void) -{ -} - -/* The "cpuid" instruction is a way of querying both the CPU identity - * (manufacturer, model, etc) and its features. It was introduced before the - * Pentium in 1993 and keeps getting extended by both Intel and AMD. As you - * might imagine, after a decade and a half this treatment, it is now a giant - * ball of hair. Its entry in the current Intel manual runs to 28 pages. - * - * This instruction even it has its own Wikipedia entry. The Wikipedia entry - * has been translated into 4 languages. I am not making this up! - * - * We could get funky here and identify ourselves as "GenuineLguest", but - * instead we just use the real "cpuid" instruction. Then I pretty much turned - * off feature bits until the Guest booted. (Don't say that: you'll damage - * lguest sales!) Shut up, inner voice! (Hey, just pointing out that this is - * hardly future proof.) Noone's listening! They don't like you anyway, - * parenthetic weirdo! - * - * Replacing the cpuid so we can turn features off is great for the kernel, but - * anyone (including userspace) can just use the raw "cpuid" instruction and - * the Host won't even notice since it isn't privileged. So we try not to get - * too worked up about it. */ -static void lguest_cpuid(unsigned int *eax, unsigned int *ebx, - unsigned int *ecx, unsigned int *edx) -{ - int function = *eax; - - native_cpuid(eax, ebx, ecx, edx); - switch (function) { - case 1: /* Basic feature request. */ - /* We only allow kernel to see SSE3, CMPXCHG16B and SSSE3 */ - *ecx &= 0x00002201; - /* SSE, SSE2, FXSR, MMX, CMOV, CMPXCHG8B, FPU. */ - *edx &= 0x07808101; - /* The Host can do a nice optimization if it knows that the - * kernel mappings (addresses above 0xC0000000 or whatever - * PAGE_OFFSET is set to) haven't changed. But Linux calls - * flush_tlb_user() for both user and kernel mappings unless - * the Page Global Enable (PGE) feature bit is set. */ - *edx |= 0x00002000; - break; - case 0x80000000: - /* Futureproof this a little: if they ask how much extended - * processor information there is, limit it to known fields. */ - if (*eax > 0x80000008) - *eax = 0x80000008; - break; - } -} - -/* Intel has four control registers, imaginatively named cr0, cr2, cr3 and cr4. - * I assume there's a cr1, but it hasn't bothered us yet, so we'll not bother - * it. The Host needs to know when the Guest wants to change them, so we have - * a whole series of functions like read_cr0() and write_cr0(). - * - * We start with CR0. CR0 allows you to turn on and off all kinds of basic - * features, but Linux only really cares about one: the horrifically-named Task - * Switched (TS) bit at bit 3 (ie. 8) - * - * What does the TS bit do? Well, it causes the CPU to trap (interrupt 7) if - * the floating point unit is used. Which allows us to restore FPU state - * lazily after a task switch, and Linux uses that gratefully, but wouldn't a - * name like "FPUTRAP bit" be a little less cryptic? - * - * We store cr0 (and cr3) locally, because the Host never changes it. The - * Guest sometimes wants to read it and we'd prefer not to bother the Host - * unnecessarily. */ -static unsigned long current_cr0, current_cr3; -static void lguest_write_cr0(unsigned long val) -{ - /* 8 == TS bit. */ - lazy_hcall(LHCALL_TS, val & 8, 0, 0); - current_cr0 = val; -} - -static unsigned long lguest_read_cr0(void) -{ - return current_cr0; -} - -/* Intel provided a special instruction to clear the TS bit for people too cool - * to use write_cr0() to do it. This "clts" instruction is faster, because all - * the vowels have been optimized out. */ -static void lguest_clts(void) -{ - lazy_hcall(LHCALL_TS, 0, 0, 0); - current_cr0 &= ~8U; -} - -/* CR2 is the virtual address of the last page fault, which the Guest only ever - * reads. The Host kindly writes this into our "struct lguest_data", so we - * just read it out of there. */ -static unsigned long lguest_read_cr2(void) -{ - return lguest_data.cr2; -} - -/* CR3 is the current toplevel pagetable page: the principle is the same as - * cr0. Keep a local copy, and tell the Host when it changes. */ -static void lguest_write_cr3(unsigned long cr3) -{ - lazy_hcall(LHCALL_NEW_PGTABLE, cr3, 0, 0); - current_cr3 = cr3; -} - -static unsigned long lguest_read_cr3(void) -{ - return current_cr3; -} - -/* CR4 is used to enable and disable PGE, but we don't care. */ -static unsigned long lguest_read_cr4(void) -{ - return 0; -} - -static void lguest_write_cr4(unsigned long val) -{ -} - -/* - * Page Table Handling. - * - * Now would be a good time to take a rest and grab a coffee or similarly - * relaxing stimulant. The easy parts are behind us, and the trek gradually - * winds uphill from here. - * - * Quick refresher: memory is divided into "pages" of 4096 bytes each. The CPU - * maps virtual addresses to physical addresses using "page tables". We could - * use one huge index of 1 million entries: each address is 4 bytes, so that's - * 1024 pages just to hold the page tables. But since most virtual addresses - * are unused, we use a two level index which saves space. The CR3 register - * contains the physical address of the top level "page directory" page, which - * contains physical addresses of up to 1024 second-level pages. Each of these - * second level pages contains up to 1024 physical addresses of actual pages, - * or Page Table Entries (PTEs). - * - * Here's a diagram, where arrows indicate physical addresses: - * - * CR3 ---> +---------+ - * | --------->+---------+ - * | | | PADDR1 | - * Top-level | | PADDR2 | - * (PMD) page | | | - * | | Lower-level | - * | | (PTE) page | - * | | | | - * .... .... - * - * So to convert a virtual address to a physical address, we look up the top - * level, which points us to the second level, which gives us the physical - * address of that page. If the top level entry was not present, or the second - * level entry was not present, then the virtual address is invalid (we - * say "the page was not mapped"). - * - * Put another way, a 32-bit virtual address is divided up like so: - * - * 1 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 - * |<---- 10 bits ---->|<---- 10 bits ---->|<------ 12 bits ------>| - * Index into top Index into second Offset within page - * page directory page pagetable page - * - * The kernel spends a lot of time changing both the top-level page directory - * and lower-level pagetable pages. The Guest doesn't know physical addresses, - * so while it maintains these page tables exactly like normal, it also needs - * to keep the Host informed whenever it makes a change: the Host will create - * the real page tables based on the Guests'. - */ - -/* The Guest calls this to set a second-level entry (pte), ie. to map a page - * into a process' address space. We set the entry then tell the Host the - * toplevel and address this corresponds to. The Guest uses one pagetable per - * process, so we need to tell the Host which one we're changing (mm->pgd). */ -static void lguest_set_pte_at(struct mm_struct *mm, unsigned long addr, - pte_t *ptep, pte_t pteval) -{ - *ptep = pteval; - lazy_hcall(LHCALL_SET_PTE, __pa(mm->pgd), addr, pteval.pte_low); -} - -/* The Guest calls this to set a top-level entry. Again, we set the entry then - * tell the Host which top-level page we changed, and the index of the entry we - * changed. */ -static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval) -{ - *pmdp = pmdval; - lazy_hcall(LHCALL_SET_PMD, __pa(pmdp)&PAGE_MASK, - (__pa(pmdp)&(PAGE_SIZE-1))/4, 0); -} - -/* There are a couple of legacy places where the kernel sets a PTE, but we - * don't know the top level any more. This is useless for us, since we don't - * know which pagetable is changing or what address, so we just tell the Host - * to forget all of them. Fortunately, this is very rare. - * - * ... except in early boot when the kernel sets up the initial pagetables, - * which makes booting astonishingly slow. So we don't even tell the Host - * anything changed until we've done the first page table switch. - */ -static void lguest_set_pte(pte_t *ptep, pte_t pteval) -{ - *ptep = pteval; - /* Don't bother with hypercall before initial setup. */ - if (current_cr3) - lazy_hcall(LHCALL_FLUSH_TLB, 1, 0, 0); -} - -/* Unfortunately for Lguest, the pv_mmu_ops for page tables were based on - * native page table operations. On native hardware you can set a new page - * table entry whenever you want, but if you want to remove one you have to do - * a TLB flush (a TLB is a little cache of page table entries kept by the CPU). - * - * So the lguest_set_pte_at() and lguest_set_pmd() functions above are only - * called when a valid entry is written, not when it's removed (ie. marked not - * present). Instead, this is where we come when the Guest wants to remove a - * page table entry: we tell the Host to set that entry to 0 (ie. the present - * bit is zero). */ -static void lguest_flush_tlb_single(unsigned long addr) -{ - /* Simply set it to zero: if it was not, it will fault back in. */ - lazy_hcall(LHCALL_SET_PTE, current_cr3, addr, 0); -} - -/* This is what happens after the Guest has removed a large number of entries. - * This tells the Host that any of the page table entries for userspace might - * have changed, ie. virtual addresses below PAGE_OFFSET. */ -static void lguest_flush_tlb_user(void) -{ - lazy_hcall(LHCALL_FLUSH_TLB, 0, 0, 0); -} - -/* This is called when the kernel page tables have changed. That's not very - * common (unless the Guest is using highmem, which makes the Guest extremely - * slow), so it's worth separating this from the user flushing above. */ -static void lguest_flush_tlb_kernel(void) -{ - lazy_hcall(LHCALL_FLUSH_TLB, 1, 0, 0); -} - -/* - * The Unadvanced Programmable Interrupt Controller. - * - * This is an attempt to implement the simplest possible interrupt controller. - * I spent some time looking though routines like set_irq_chip_and_handler, - * set_irq_chip_and_handler_name, set_irq_chip_data and set_phasers_to_stun and - * I *think* this is as simple as it gets. - * - * We can tell the Host what interrupts we want blocked ready for using the - * lguest_data.interrupts bitmap, so disabling (aka "masking") them is as - * simple as setting a bit. We don't actually "ack" interrupts as such, we - * just mask and unmask them. I wonder if we should be cleverer? - */ -static void disable_lguest_irq(unsigned int irq) -{ - set_bit(irq, lguest_data.blocked_interrupts); -} - -static void enable_lguest_irq(unsigned int irq) -{ - clear_bit(irq, lguest_data.blocked_interrupts); -} - -/* This structure describes the lguest IRQ controller. */ -static struct irq_chip lguest_irq_controller = { - .name = "lguest", - .mask = disable_lguest_irq, - .mask_ack = disable_lguest_irq, - .unmask = enable_lguest_irq, -}; - -/* This sets up the Interrupt Descriptor Table (IDT) entry for each hardware - * interrupt (except 128, which is used for system calls), and then tells the - * Linux infrastructure that each interrupt is controlled by our level-based - * lguest interrupt controller. */ -static void __init lguest_init_IRQ(void) -{ - unsigned int i; - - for (i = 0; i < LGUEST_IRQS; i++) { - int vector = FIRST_EXTERNAL_VECTOR + i; - if (vector != SYSCALL_VECTOR) { - set_intr_gate(vector, interrupt[i]); - set_irq_chip_and_handler(i, &lguest_irq_controller, - handle_level_irq); - } - } - /* This call is required to set up for 4k stacks, where we have - * separate stacks for hard and soft interrupts. */ - irq_ctx_init(smp_processor_id()); -} - -/* - * Time. - * - * It would be far better for everyone if the Guest had its own clock, but - * until then the Host gives us the time on every interrupt. - */ -static unsigned long lguest_get_wallclock(void) -{ - return lguest_data.time.tv_sec; -} - -static cycle_t lguest_clock_read(void) -{ - unsigned long sec, nsec; - - /* If the Host tells the TSC speed, we can trust that. */ - if (lguest_data.tsc_khz) - return native_read_tsc(); - - /* If we can't use the TSC, we read the time value written by the Host. - * Since it's in two parts (seconds and nanoseconds), we risk reading - * it just as it's changing from 99 & 0.999999999 to 100 and 0, and - * getting 99 and 0. As Linux tends to come apart under the stress of - * time travel, we must be careful: */ - do { - /* First we read the seconds part. */ - sec = lguest_data.time.tv_sec; - /* This read memory barrier tells the compiler and the CPU that - * this can't be reordered: we have to complete the above - * before going on. */ - rmb(); - /* Now we read the nanoseconds part. */ - nsec = lguest_data.time.tv_nsec; - /* Make sure we've done that. */ - rmb(); - /* Now if the seconds part has changed, try again. */ - } while (unlikely(lguest_data.time.tv_sec != sec)); - - /* Our non-TSC clock is in real nanoseconds. */ - return sec*1000000000ULL + nsec; -} - -/* This is what we tell the kernel is our clocksource. */ -static struct clocksource lguest_clock = { - .name = "lguest", - .rating = 400, - .read = lguest_clock_read, - .mask = CLOCKSOURCE_MASK(64), - .mult = 1 << 22, - .shift = 22, -}; - -/* The "scheduler clock" is just our real clock, adjusted to start at zero */ -static unsigned long long lguest_sched_clock(void) -{ - return cyc2ns(&lguest_clock, lguest_clock_read() - clock_base); -} - -/* We also need a "struct clock_event_device": Linux asks us to set it to go - * off some time in the future. Actually, James Morris figured all this out, I - * just applied the patch. */ -static int lguest_clockevent_set_next_event(unsigned long delta, - struct clock_event_device *evt) -{ - if (delta < LG_CLOCK_MIN_DELTA) { - if (printk_ratelimit()) - printk(KERN_DEBUG "%s: small delta %lu ns\n", - __FUNCTION__, delta); - return -ETIME; - } - hcall(LHCALL_SET_CLOCKEVENT, delta, 0, 0); - return 0; -} - -static void lguest_clockevent_set_mode(enum clock_event_mode mode, - struct clock_event_device *evt) -{ - switch (mode) { - case CLOCK_EVT_MODE_UNUSED: - case CLOCK_EVT_MODE_SHUTDOWN: - /* A 0 argument shuts the clock down. */ - hcall(LHCALL_SET_CLOCKEVENT, 0, 0, 0); - break; - case CLOCK_EVT_MODE_ONESHOT: - /* This is what we expect. */ - break; - case CLOCK_EVT_MODE_PERIODIC: - BUG(); - case CLOCK_EVT_MODE_RESUME: - break; - } -} - -/* This describes our primitive timer chip. */ -static struct clock_event_device lguest_clockevent = { - .name = "lguest", - .features = CLOCK_EVT_FEAT_ONESHOT, - .set_next_event = lguest_clockevent_set_next_event, - .set_mode = lguest_clockevent_set_mode, - .rating = INT_MAX, - .mult = 1, - .shift = 0, - .min_delta_ns = LG_CLOCK_MIN_DELTA, - .max_delta_ns = LG_CLOCK_MAX_DELTA, -}; - -/* This is the Guest timer interrupt handler (hardware interrupt 0). We just - * call the clockevent infrastructure and it does whatever needs doing. */ -static void lguest_time_irq(unsigned int irq, struct irq_desc *desc) -{ - unsigned long flags; - - /* Don't interrupt us while this is running. */ - local_irq_save(flags); - lguest_clockevent.event_handler(&lguest_clockevent); - local_irq_restore(flags); -} - -/* At some point in the boot process, we get asked to set up our timing - * infrastructure. The kernel doesn't expect timer interrupts before this, but - * we cleverly initialized the "blocked_interrupts" field of "struct - * lguest_data" so that timer interrupts were blocked until now. */ -static void lguest_time_init(void) -{ - /* Set up the timer interrupt (0) to go to our simple timer routine */ - set_irq_handler(0, lguest_time_irq); - - /* Our clock structure look like arch/i386/kernel/tsc.c if we can use - * the TSC, otherwise it's a dumb nanosecond-resolution clock. Either - * way, the "rating" is initialized so high that it's always chosen - * over any other clocksource. */ - if (lguest_data.tsc_khz) { - lguest_clock.mult = clocksource_khz2mult(lguest_data.tsc_khz, - lguest_clock.shift); - lguest_clock.flags = CLOCK_SOURCE_IS_CONTINUOUS; - } - clock_base = lguest_clock_read(); - clocksource_register(&lguest_clock); - - /* Now we've set up our clock, we can use it as the scheduler clock */ - pv_time_ops.sched_clock = lguest_sched_clock; - - /* We can't set cpumask in the initializer: damn C limitations! Set it - * here and register our timer device. */ - lguest_clockevent.cpumask = cpumask_of_cpu(0); - clockevents_register_device(&lguest_clockevent); - - /* Finally, we unblock the timer interrupt. */ - enable_lguest_irq(0); -} - -/* - * Miscellaneous bits and pieces. - * - * Here is an oddball collection of functions which the Guest needs for things - * to work. They're pretty simple. - */ - -/* The Guest needs to tell the host what stack it expects traps to use. For - * native hardware, this is part of the Task State Segment mentioned above in - * lguest_load_tr_desc(), but to help hypervisors there's this special call. - * - * We tell the Host the segment we want to use (__KERNEL_DS is the kernel data - * segment), the privilege level (we're privilege level 1, the Host is 0 and - * will not tolerate us trying to use that), the stack pointer, and the number - * of pages in the stack. */ -static void lguest_load_esp0(struct tss_struct *tss, - struct thread_struct *thread) -{ - lazy_hcall(LHCALL_SET_STACK, __KERNEL_DS|0x1, thread->esp0, - THREAD_SIZE/PAGE_SIZE); -} - -/* Let's just say, I wouldn't do debugging under a Guest. */ -static void lguest_set_debugreg(int regno, unsigned long value) -{ - /* FIXME: Implement */ -} - -/* There are times when the kernel wants to make sure that no memory writes are - * caught in the cache (that they've all reached real hardware devices). This - * doesn't matter for the Guest which has virtual hardware. - * - * On the Pentium 4 and above, cpuid() indicates that the Cache Line Flush - * (clflush) instruction is available and the kernel uses that. Otherwise, it - * uses the older "Write Back and Invalidate Cache" (wbinvd) instruction. - * Unlike clflush, wbinvd can only be run at privilege level 0. So we can - * ignore clflush, but replace wbinvd. - */ -static void lguest_wbinvd(void) -{ -} - -/* If the Guest expects to have an Advanced Programmable Interrupt Controller, - * we play dumb by ignoring writes and returning 0 for reads. So it's no - * longer Programmable nor Controlling anything, and I don't think 8 lines of - * code qualifies for Advanced. It will also never interrupt anything. It - * does, however, allow us to get through the Linux boot code. */ -#ifdef CONFIG_X86_LOCAL_APIC -static void lguest_apic_write(unsigned long reg, unsigned long v) -{ -} - -static unsigned long lguest_apic_read(unsigned long reg) -{ - return 0; -} -#endif - -/* STOP! Until an interrupt comes in. */ -static void lguest_safe_halt(void) -{ - hcall(LHCALL_HALT, 0, 0, 0); -} - -/* Perhaps CRASH isn't the best name for this hypercall, but we use it to get a - * message out when we're crashing as well as elegant termination like powering - * off. - * - * Note that the Host always prefers that the Guest speak in physical addresses - * rather than virtual addresses, so we use __pa() here. */ -static void lguest_power_off(void) -{ - hcall(LHCALL_CRASH, __pa("Power down"), 0, 0); -} - -/* - * Panicing. - * - * Don't. But if you did, this is what happens. - */ -static int lguest_panic(struct notifier_block *nb, unsigned long l, void *p) -{ - hcall(LHCALL_CRASH, __pa(p), 0, 0); - /* The hcall won't return, but to keep gcc happy, we're "done". */ - return NOTIFY_DONE; -} - -static struct notifier_block paniced = { - .notifier_call = lguest_panic -}; - -/* Setting up memory is fairly easy. */ -static __init char *lguest_memory_setup(void) -{ - /* We do this here and not earlier because lockcheck barfs if we do it - * before start_kernel() */ - atomic_notifier_chain_register(&panic_notifier_list, &paniced); - - /* The Linux bootloader header contains an "e820" memory map: the - * Launcher populated the first entry with our memory limit. */ - add_memory_region(boot_params.e820_map[0].addr, - boot_params.e820_map[0].size, - boot_params.e820_map[0].type); - - /* This string is for the boot messages. */ - return "LGUEST"; -} - -/*G:050 - * Patching (Powerfully Placating Performance Pedants) - * - * We have already seen that pv_ops structures let us replace simple - * native instructions with calls to the appropriate back end all throughout - * the kernel. This allows the same kernel to run as a Guest and as a native - * kernel, but it's slow because of all the indirect branches. - * - * Remember that David Wheeler quote about "Any problem in computer science can - * be solved with another layer of indirection"? The rest of that quote is - * "... But that usually will create another problem." This is the first of - * those problems. - * - * Our current solution is to allow the paravirt back end to optionally patch - * over the indirect calls to replace them with something more efficient. We - * patch the four most commonly called functions: disable interrupts, enable - * interrupts, restore interrupts and save interrupts. We usually have 10 - * bytes to patch into: the Guest versions of these operations are small enough - * that we can fit comfortably. - * - * First we need assembly templates of each of the patchable Guest operations, - * and these are in lguest_asm.S. */ - -/*G:060 We construct a table from the assembler templates: */ -static const struct lguest_insns -{ - const char *start, *end; -} lguest_insns[] = { - [PARAVIRT_PATCH(pv_irq_ops.irq_disable)] = { lgstart_cli, lgend_cli }, - [PARAVIRT_PATCH(pv_irq_ops.irq_enable)] = { lgstart_sti, lgend_sti }, - [PARAVIRT_PATCH(pv_irq_ops.restore_fl)] = { lgstart_popf, lgend_popf }, - [PARAVIRT_PATCH(pv_irq_ops.save_fl)] = { lgstart_pushf, lgend_pushf }, -}; - -/* Now our patch routine is fairly simple (based on the native one in - * paravirt.c). If we have a replacement, we copy it in and return how much of - * the available space we used. */ -static unsigned lguest_patch(u8 type, u16 clobber, void *ibuf, - unsigned long addr, unsigned len) -{ - unsigned int insn_len; - - /* Don't do anything special if we don't have a replacement */ - if (type >= ARRAY_SIZE(lguest_insns) || !lguest_insns[type].start) - return paravirt_patch_default(type, clobber, ibuf, addr, len); - - insn_len = lguest_insns[type].end - lguest_insns[type].start; - - /* Similarly if we can't fit replacement (shouldn't happen, but let's - * be thorough). */ - if (len < insn_len) - return paravirt_patch_default(type, clobber, ibuf, addr, len); - - /* Copy in our instructions. */ - memcpy(ibuf, lguest_insns[type].start, insn_len); - return insn_len; -} - -/*G:030 Once we get to lguest_init(), we know we're a Guest. The pv_ops - * structures in the kernel provide points for (almost) every routine we have - * to override to avoid privileged instructions. */ -__init void lguest_init(void *boot) -{ - /* Copy boot parameters first: the Launcher put the physical location - * in %esi, and head.S converted that to a virtual address and handed - * it to us. We use "__memcpy" because "memcpy" sometimes tries to do - * tricky things to go faster, and we're not ready for that. */ - __memcpy(&boot_params, boot, PARAM_SIZE); - /* The boot parameters also tell us where the command-line is: save - * that, too. */ - __memcpy(boot_command_line, __va(boot_params.hdr.cmd_line_ptr), - COMMAND_LINE_SIZE); - - /* We're under lguest, paravirt is enabled, and we're running at - * privilege level 1, not 0 as normal. */ - pv_info.name = "lguest"; - pv_info.paravirt_enabled = 1; - pv_info.kernel_rpl = 1; - - /* We set up all the lguest overrides for sensitive operations. These - * are detailed with the operations themselves. */ - - /* interrupt-related operations */ - pv_irq_ops.init_IRQ = lguest_init_IRQ; - pv_irq_ops.save_fl = save_fl; - pv_irq_ops.restore_fl = restore_fl; - pv_irq_ops.irq_disable = irq_disable; - pv_irq_ops.irq_enable = irq_enable; - pv_irq_ops.safe_halt = lguest_safe_halt; - - /* init-time operations */ - pv_init_ops.memory_setup = lguest_memory_setup; - pv_init_ops.patch = lguest_patch; - - /* Intercepts of various cpu instructions */ - pv_cpu_ops.load_gdt = lguest_load_gdt; - pv_cpu_ops.cpuid = lguest_cpuid; - pv_cpu_ops.load_idt = lguest_load_idt; - pv_cpu_ops.iret = lguest_iret; - pv_cpu_ops.load_esp0 = lguest_load_esp0; - pv_cpu_ops.load_tr_desc = lguest_load_tr_desc; - pv_cpu_ops.set_ldt = lguest_set_ldt; - pv_cpu_ops.load_tls = lguest_load_tls; - pv_cpu_ops.set_debugreg = lguest_set_debugreg; - pv_cpu_ops.clts = lguest_clts; - pv_cpu_ops.read_cr0 = lguest_read_cr0; - pv_cpu_ops.write_cr0 = lguest_write_cr0; - pv_cpu_ops.read_cr4 = lguest_read_cr4; - pv_cpu_ops.write_cr4 = lguest_write_cr4; - pv_cpu_ops.write_gdt_entry = lguest_write_gdt_entry; - pv_cpu_ops.write_idt_entry = lguest_write_idt_entry; - pv_cpu_ops.wbinvd = lguest_wbinvd; - pv_cpu_ops.lazy_mode.enter = paravirt_enter_lazy_cpu; - pv_cpu_ops.lazy_mode.leave = lguest_leave_lazy_mode; - - /* pagetable management */ - pv_mmu_ops.write_cr3 = lguest_write_cr3; - pv_mmu_ops.flush_tlb_user = lguest_flush_tlb_user; - pv_mmu_ops.flush_tlb_single = lguest_flush_tlb_single; - pv_mmu_ops.flush_tlb_kernel = lguest_flush_tlb_kernel; - pv_mmu_ops.set_pte = lguest_set_pte; - pv_mmu_ops.set_pte_at = lguest_set_pte_at; - pv_mmu_ops.set_pmd = lguest_set_pmd; - pv_mmu_ops.read_cr2 = lguest_read_cr2; - pv_mmu_ops.read_cr3 = lguest_read_cr3; - pv_mmu_ops.lazy_mode.enter = paravirt_enter_lazy_mmu; - pv_mmu_ops.lazy_mode.leave = lguest_leave_lazy_mode; - -#ifdef CONFIG_X86_LOCAL_APIC - /* apic read/write intercepts */ - pv_apic_ops.apic_write = lguest_apic_write; - pv_apic_ops.apic_write_atomic = lguest_apic_write; - pv_apic_ops.apic_read = lguest_apic_read; -#endif - - /* time operations */ - pv_time_ops.get_wallclock = lguest_get_wallclock; - pv_time_ops.time_init = lguest_time_init; - - /* Now is a good time to look at the implementations of these functions - * before returning to the rest of lguest_init(). */ - - /*G:070 Now we've seen all the paravirt_ops, we return to - * lguest_init() where the rest of the fairly chaotic boot setup - * occurs. - * - * The Host expects our first hypercall to tell it where our "struct - * lguest_data" is, so we do that first. */ - hcall(LHCALL_LGUEST_INIT, __pa(&lguest_data), 0, 0); - - /* The native boot code sets up initial page tables immediately after - * the kernel itself, and sets init_pg_tables_end so they're not - * clobbered. The Launcher places our initial pagetables somewhere at - * the top of our physical memory, so we don't need extra space: set - * init_pg_tables_end to the end of the kernel. */ - init_pg_tables_end = __pa(pg0); - - /* Load the %fs segment register (the per-cpu segment register) with - * the normal data segment to get through booting. */ - asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_DS) : "memory"); - - /* Clear the part of the kernel data which is expected to be zero. - * Normally it will be anyway, but if we're loading from a bzImage with - * CONFIG_RELOCATALE=y, the relocations will be sitting here. */ - memset(__bss_start, 0, __bss_stop - __bss_start); - - /* The Host uses the top of the Guest's virtual address space for the - * Host<->Guest Switcher, and it tells us how much it needs in - * lguest_data.reserve_mem, set up on the LGUEST_INIT hypercall. */ - reserve_top_address(lguest_data.reserve_mem); - - /* If we don't initialize the lock dependency checker now, it crashes - * paravirt_disable_iospace. */ - lockdep_init(); - - /* The IDE code spends about 3 seconds probing for disks: if we reserve - * all the I/O ports up front it can't get them and so doesn't probe. - * Other device drivers are similar (but less severe). This cuts the - * kernel boot time on my machine from 4.1 seconds to 0.45 seconds. */ - paravirt_disable_iospace(); - - /* This is messy CPU setup stuff which the native boot code does before - * start_kernel, so we have to do, too: */ - cpu_detect(&new_cpu_data); - /* head.S usually sets up the first capability word, so do it here. */ - new_cpu_data.x86_capability[0] = cpuid_edx(1); - - /* Math is always hard! */ - new_cpu_data.hard_math = 1; - -#ifdef CONFIG_X86_MCE - mce_disabled = 1; -#endif -#ifdef CONFIG_ACPI - acpi_disabled = 1; - acpi_ht = 0; -#endif - - /* We set the perferred console to "hvc". This is the "hypervisor - * virtual console" driver written by the PowerPC people, which we also - * adapted for lguest's use. */ - add_preferred_console("hvc", 0, NULL); - - /* Last of all, we set the power management poweroff hook to point to - * the Guest routine to power off. */ - pm_power_off = lguest_power_off; - - /* Now we're set up, call start_kernel() in init/main.c and we proceed - * to boot as normal. It never returns. */ - start_kernel(); -} -/* - * This marks the end of stage II of our journey, The Guest. - * - * It is now time for us to explore the nooks and crannies of the three Guest - * devices and complete our understanding of the Guest in "make Drivers". - */ |