summaryrefslogtreecommitdiff
path: root/drivers/kvm
AgeCommit message (Collapse)Author
2007-02-09[PATCH] misc NULL noise removalAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-09[PATCH] kvm: NULL noise removalAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-09[PATCH] kvm: __user annotationsAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-01[PATCH] KVM: fix lockup on 32-bit intel hosts with nx disabled in the biosAvi Kivity
Intel hosts, without long mode, and with nx support disabled in the bios have an efer that is readable but not writable. This causes a lockup on switch to guest mode (even though it should exit with reason 34 according to the documentation). Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-30[PATCH] Fix "CONFIG_X86_64_" typo in drivers/kvm/svm.cRobert P. J. Day
Fix what looks like an obvious typo in the file drivers/kvm/svm.c. Signed-off-by: Robert P. J. Day <rpjday@mindspring.com> Acked-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-26[PATCH] KVM: SVM: Propagate cpu shutdown events to userspaceJoerg Roedel
This patch implements forwarding of SHUTDOWN intercepts from the guest on to userspace on AMD SVM. A SHUTDOWN event occurs when the guest produces a triple fault (e.g. on reboot). This also fixes the bug that a guest reboot actually causes a host reboot under some circumstances. Signed-off-by: Joerg Roedel <joerg.roedel@amd.com> Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-26[PATCH] KVM: MMU: Report nx faults to the guestAvi Kivity
With the recent guest page fault change, we perform access checks on our own instead of relying on the cpu. This means we have to perform the nx checks as well. Software like the google toolbar on windows appears to rely on this somehow. Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-26[PATCH] KVM: MMU: Perform access checks in walk_addr()Avi Kivity
Check pte permission bits in walk_addr(), instead of scattering the checks all over the code. This has the following benefits: 1. We no longer set the accessed bit for accessed which fail permission checks. 2. Setting the accessed bit is simplified. 3. Under some circumstances, we used to pretend a page fault was fixed when it would actually fail the access checks. This caused an unnecessary vmexit. 4. The error code for guest page faults is now correct. The fix helps netbsd further along booting, and allows kvm to pass the new mmu testsuite. Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-26[PATCH] KVM: Emulate IA32_MISC_ENABLE msrAvi Kivity
This allows netbsd 3.1 i386 to get further along installing. Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-26[PATCH] KVM: SVM: Fix SVM idt confusionLeonard Norrgard
There's an obvious typo in svm_{get,set}_idt, causing it to access the ldt instead. Because these functions are only called for save/load on AMD, the bug does not impact normal operation. With the fix, save/load works as expected on AMD hosts. Signed-off-by: Uri Lublin <uril@qumranet.com> Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-23[PATCH] KVM: fix bogus pagefault on writable pagesAvi Kivity
If a page is marked as dirty in the guest pte, set_pte_common() can set the writable bit on newly-instantiated shadow pte. This optimization avoids a write fault after the initial read fault. However, if a write fault instantiates the pte, fix_write_pf() incorrectly reports the fault as a guest page fault, and the guest oopses on what appears to be a correctly-mapped page. Fix is to detect the condition and only report a guest page fault on a user access to a kernel page. With the fix, a kvm guest can survive a whole night of running the kernel hacker's screensaver (make -j9 in a loop). Signed-off-by: Avi Kivity <avi@qumranet.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-23[PATCH] KVM: x86 emulator: fix bit string instructionsAvi Kivity
The various bit string instructions (bts, btc, etc.) fail to adjust the address correctly if the bit address is beyond BITS_PER_LONG. This bug creeped in as the emulator originally relied on cr2 to contain the memory address; however we now decode it from the mod r/m bits, and must adjust the offset to account for large bit indices. The patch is rather large because it switches src and dst decoding around, so that the bit index is available when decoding the memory address. This fixes workloads like the FC5 installer. Signed-off-by: Avi Kivity <avi@qumranet.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-23[PATCH] KVM: fix race between mmio reads and injected interruptsAvi Kivity
The kvm mmio read path looks like: 1. guest read faults 2. kvm emulates read, calls emulator_read_emulated() 3. fails as a read requires userspace help 4. exit to userspace 5. userspace emulates read, kvm sets vcpu->mmio_read_completed 6. re-enter guest, fault again 7. kvm emulates read, calls emulator_read_emulated() 8. succeeds as vcpu->mmio_read_emulated is set 9. instruction completes and guest is resumed A problem surfaces if the userspace exit (step 5) also requests an interrupt injection. In that case, the guest does not re-execute the original instruction, but the interrupt handler. The next time an mmio read is exectued (likely for a different address), step 3 will find vcpu->mmio_read_completed set and return the value read for the original instruction. The problem manifested itself in a few annoying ways: - little squares appear randomly on console when switching virtual terminals - ne2000 fails under nfs read load - rtl8139 complains about "pci errors" even though the device model is incapable of issuing them. Fix by skipping interrupt injection if an mmio read is pending. A better fix is to avoid re-entry into the guest, and re-emulating immediately instead. However that's a bit more complex. Signed-off-by: Avi Kivity <avi@qumranet.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-23[PATCH] KVM: make sure there is a vcpu context loaded when destroying the mmuAvi Kivity
This makes the vmwrite errors on vm shutdown go away. Signed-off-by: Avi Kivity <avi@qumranet.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-22[PATCH] vmx: Fix register constraint in launch codeHerbert Xu
Both "=r" and "=g" breaks my build on i386: $ make CC [M] drivers/kvm/vmx.o {standard input}: Assembler messages: {standard input}:3318: Error: bad register name `%sil' make[1]: *** [drivers/kvm/vmx.o] Error 1 make: *** [_module_drivers/kvm] Error 2 The reason is that setbe requires an 8-bit register but "=r" does not constrain the target register to be one that has an 8-bit version on i386. According to http://gcc.gnu.org/bugzilla/show_bug.cgi?id=10153 the correct constraint is "=q". Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-11[PATCH] KVM: add VM-exit profilingIngo Molnar
This adds the profile=kvm boot option, which enables KVM to profile VM exits. Use: "readprofile -m ./System.map | sort -n" to see the resulting output: [...] 18246 serial_out 148.3415 18945 native_flush_tlb 378.9000 23618 serial_in 212.7748 29279 __spin_unlock_irq 622.9574 43447 native_apic_write 2068.9048 52702 enable_8259A_irq 742.2817 54250 vgacon_scroll 89.3740 67394 ide_inb 6126.7273 79514 copy_page_range 98.1654 84868 do_wp_page 86.6000 140266 pit_read 783.6089 151436 ide_outb 25239.3333 152668 native_io_delay 21809.7143 174783 mask_and_ack_8259A 783.7803 362404 native_set_pte_at 36240.4000 1688747 total 0.5009 Signed-off-by: Ingo Molnar <mingo@elte.hu> Acked-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: Simplify test for interrupt windowDor Laor
No need to test for rflags.if as both VT and SVM specs assure us that on exit caused from interrupt window opening, 'if' is set. Signed-off-by: Dor Laor <dor.laor@qumranet.com> Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: Simplify mmu_alloc_roots()Ingo Molnar
Small optimization/cleanup: page == page_header(page->page_hpa) Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: Make loading cr3 more robustIngo Molnar
Prevent the guest's loading of a corrupt cr3 (pointing at no guest phsyical page) from crashing the host. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Add missing dirty bitAvi Kivity
If we emulate a write, we fail to set the dirty bit on the guest pte, leading the guest to believe the page is clean, and thus lose data. Bad. Fix by setting the guest pte dirty bit under such conditions. Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: Don't set guest cr3 from vmx_vcpu_setup()Avi Kivity
It overwrites the right cr3 set from mmu setup. Happens only with the test harness. Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: Add missing 'break'Avi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: Avoid oom on cr3 switchIngo Molnar
Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: Initialize vcpu->kvm a little earlierAvi Kivity
Fixes oops on early close of /dev/kvm. Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: Improve reporting of vmwrite errorsAvi Kivity
This will allow us to see the root cause when a vmwrite error happens. Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: add audit code to check mappings, etc are correctAvi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Destroy mmu while we still have a vcpu leftAvi Kivity
mmu_destroy flushes the guest tlb (indirectly), which needs a valid vcpu. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Flush guest tlb when reducing permissions on a pteAvi Kivity
If we reduce permissions on a pte, we must flush the cached copy of the pte from the guest's tlb. This is implemented at the moment by flushing the entire guest tlb, and can be improved by flushing just the relevant virtual address, if it is known. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Detect oom conditions and propagate error to userspaceAvi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Replace atomic allocations by preallocated objectsAvi Kivity
The mmu sometimes needs memory for reverse mapping and parent pte chains. however, we can't allocate from within the mmu because of the atomic context. So, move the allocations to a central place that can be executed before the main mmu machinery, where we can bail out on failure before any damage is done. (error handling is deffered for now, but the basic structure is there) Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Free pages on kvm destructionAvi Kivity
Because mmu pages have attached rmap and parent pte chain structures, we need to zap them before freeing so the attached structures are freed. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Treat user-mode faults as a hint that a page is no longer ↵Avi Kivity
a page table Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Fix cmpxchg8b emulationAvi Kivity
cmpxchg8b uses edx:eax as the compare operand, not edi:eax. cmpxchg8b is used by 32-bit pae guests to set page table entries atomically, and this is emulated touching shadowed guest page tables. Also, implement it for 32-bit hosts. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Never free a shadow page actively serving as a rootAvi Kivity
We always need cr3 to point to something valid, so if we detect that we're freeing a root page, simply push it back to the top of the active list. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Page table write flood protectionAvi Kivity
In fork() (or when we protect a page that is no longer a page table), we can experience floods of writes to a page, which have to be emulated. This is expensive. So, if we detect such a flood, zap the page so subsequent writes can proceed natively. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: If an empty shadow page is not empty, report more infoAvi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Ensure freed shadow pages are cleanAvi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: <ove is_empty_shadow_page() above kvm_mmu_free_page()Avi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Handle misaligned accesses to write protected guest page ↵Avi Kivity
tables A misaligned access affects two shadow ptes instead of just one. Since a misaligned access is unlikely to occur on a real page table, just zap the page out of existence, avoiding further trouble. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Remove release_pt_page_64()Avi Kivity
Unused. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Remove invlpg interceptionAvi Kivity
Since we write protect shadowed guest page tables, there is no need to trap page invalidations (the guest will always change the mapping before issuing the invlpg instruction). Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: oom handlingAvi Kivity
When beginning to process a page fault, make sure we have enough shadow pages available to service the fault. If not, free some pages. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: kvm_mmu_put_page() only removes one link to the pageAvi Kivity
... and so must not free it unconditionally. Move the freeing to kvm_mmu_zap_page(). Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Implement child shadow unlinkingAvi Kivity
When removing a page table, we must maintain the parent_pte field all child shadow page tables. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: If emulating an instruction fails, try unprotecting the pageAvi Kivity
A page table may have been recycled into a regular page, and so any instruction can be executed on it. Unprotect the page and let the cpu do its thing. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Zap shadow page table entries on writes to guest page tablesAvi Kivity
Iterate over all shadow pages which correspond to a the given guest page table and remove the mappings. A subsequent page fault will reestablish the new mapping. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Support emulated writes into RAMAvi Kivity
As the mmu write protects guest page table, we emulate those writes. Since they are not mmio, there is no need to go to userspace to perform them. So, perform the writes in the kernel if possible, and notify the mmu about them so it can take the approriate action. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Let the walker extract the target page gfn from the pteAvi Kivity
This fixes a problem where set_pte_common() looked for shadowed pages based on the page directory gfn (a huge page) instead of the actual gfn being mapped. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Write protect guest pages when a shadow is created for themAvi Kivity
When we cache a guest page table into a shadow page table, we need to prevent further access to that page by the guest, as that would render the cache incoherent. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Shadow page table cachingAvi Kivity
Define a hashtable for caching shadow page tables. Look up the cache on context switch (cr3 change) or during page faults. The key to the cache is a combination of - the guest page table frame number - the number of paging levels in the guest * we can cache real mode, 32-bit mode, pae, and long mode page tables simultaneously. this is useful for smp bootup. - the guest page table table * some kernels use a page as both a page table and a page directory. this allows multiple shadow pages to exist for that page, one per level - the "quadrant" * 32-bit mode page tables span 4MB, whereas a shadow page table spans 2MB. similarly, a 32-bit page directory spans 4GB, while a shadow page directory spans 1GB. the quadrant allows caching up to 4 shadow page tables for one guest page in one level. - a "metaphysical" bit * for real mode, and for pse pages, there is no guest page table, so set the bit to avoid write protecting the page. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>