Commit:     fce0657ff9f14f6b1f147b5fcd6db2f54c06424e
Parent:     09072daf37abbfe8e2d5018dd913f229c76190f7
Author:     Avi Kivity <[EMAIL PROTECTED]>
AuthorDate: Tue May 1 16:44:05 2007 +0300
Committer:  Avi Kivity <[EMAIL PROTECTED]>
CommitDate: Mon Jul 16 12:05:39 2007 +0300

    KVM: MMU: Respect nonpae pagetable quadrant when zapping ptes
    When a guest writes to a page that has an mmu shadow, we have to clear
    the shadow pte corresponding to the memory location touched by the guest.
    Now, in nonpae mode, a single guest page may have two or four shadow
    pages (because a nonpae page maps 4MB or 4GB, whereas the pae shadow maps
    2MB or 1GB), so we when we look up the page we find up to three additional
    aliases for the page.  Since we _clear_ the shadow pte, it doesn't matter
    except for a slight performance penalty, but if we want to _update_ the
    shadow pte instead of clearing it, it is vital that we don't modify the
    Fortunately, exactly which page is needed (the "quadrant") is easily
    computed, and is accessible in the shadow page header.  All we need is
    to ignore shadow pages from the wrong quadrants.
    Signed-off-by: Avi Kivity <[EMAIL PROTECTED]>
 drivers/kvm/mmu.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index b3a83ef..23dc461 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -1150,6 +1150,7 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
        unsigned pte_size;
        unsigned page_offset;
        unsigned misaligned;
+       unsigned quadrant;
        int level;
        int flooded = 0;
        int npte;
@@ -1202,7 +1203,10 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
                                page_offset <<= 1;
                                npte = 2;
+                       quadrant = page_offset >> PAGE_SHIFT;
                        page_offset &= ~PAGE_MASK;
+                       if (quadrant != page->role.quadrant)
+                               continue;
                spte = __va(page->page_hpa);
                spte += page_offset / sizeof(*spte);
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