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KVM: MMU: Add validate_direct_spte() helper

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Add a helper to verify that a direct shadow page is valid wrt the required
access permissions; drop the page if it is not valid.

Reviewed-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Avi Kivity
2010-07-13 14:27:07 +03:00
parent a3aa51cfaa
commit a357bd229c
2 changed files with 29 additions and 21 deletions
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23
arch/x86/kvm/mmu.c
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@ -1500,6 +1500,29 @@ static void drop_large_spte(struct kvm_vcpu *vcpu, u64 *sptep)
}
}
static void validate_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep,
unsigned direct_access)
{
if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) {
struct kvm_mmu_page *child;
/*
* For the direct sp, if the guest pte's dirty bit
* changed form clean to dirty, it will corrupt the
* sp's access: allow writable in the read-only sp,
* so we should update the spte at this point to get
* a new sp with the correct access.
*/
child = page_header(*sptep & PT64_BASE_ADDR_MASK);
if (child->role.access == direct_access)
return;
mmu_page_remove_parent_pte(child, sptep);
__set_spte(sptep, shadow_trap_nonpresent_pte);
kvm_flush_remote_tlbs(vcpu->kvm);
}
}
static void kvm_mmu_page_unlink_children(struct kvm *kvm,
struct kvm_mmu_page *sp)
{