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    Subject[PATCH 31/33] KVM: MMU: Flush guest tlb when reducing permissions on a pte
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    Date
    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>

    Index: linux-2.6/drivers/kvm/mmu.c
    ===================================================================
    --- linux-2.6.orig/drivers/kvm/mmu.c
    +++ linux-2.6/drivers/kvm/mmu.c
    @@ -383,6 +383,7 @@ static void rmap_write_protect(struct kv
    BUG_ON(!(*spte & PT_WRITABLE_MASK));
    rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
    rmap_remove(vcpu, spte);
    + kvm_arch_ops->tlb_flush(vcpu);
    *spte &= ~(u64)PT_WRITABLE_MASK;
    }
    }
    @@ -594,6 +595,7 @@ static void kvm_mmu_page_unlink_children
    rmap_remove(vcpu, &pt[i]);
    pt[i] = 0;
    }
    + kvm_arch_ops->tlb_flush(vcpu);
    return;
    }

    @@ -927,7 +929,10 @@ static inline void set_pte_common(struct
    pgprintk("%s: found shadow page for %lx, marking ro\n",
    __FUNCTION__, gfn);
    access_bits &= ~PT_WRITABLE_MASK;
    - *shadow_pte &= ~PT_WRITABLE_MASK;
    + if (is_writeble_pte(*shadow_pte)) {
    + *shadow_pte &= ~PT_WRITABLE_MASK;
    + kvm_arch_ops->tlb_flush(vcpu);
    + }
    }
    }

    -
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