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KVM: MMU: fix direct sp's access corrupted

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If the mapping is writable but the dirty flag is not set, we will find
the read-only direct sp and setup the mapping, then if the write #PF
occur, we will mark this mapping writable in the read-only direct sp,
now, other real read-only mapping will happily write it without #PF.

It may hurt guest's COW

Fixed by re-install the mapping when write #PF occur.

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Xiao Guangrong 2010-06-30 16:03:28 +08:00 committed by Avi Kivity
parent 5fd5387c89
commit 9e7b0e7fba
1 changed files with 26 additions and 2 deletions
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28
arch/x86/kvm/paging_tmpl.h
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@ -325,8 +325,32 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
break;
}
if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep))
continue;
if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) {
struct kvm_mmu_page *child;
unsigned direct_access;
if (level != gw->level)
continue;
/*
* 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.
*/
direct_access = gw->pt_access & gw->pte_access;
if (!is_dirty_gpte(gw->ptes[gw->level - 1]))
direct_access &= ~ACC_WRITE_MASK;
child = page_header(*sptep & PT64_BASE_ADDR_MASK);
if (child->role.access == direct_access)
continue;
mmu_page_remove_parent_pte(child, sptep);
__set_spte(sptep, shadow_trap_nonpresent_pte);
kvm_flush_remote_tlbs(vcpu->kvm);
}
if (is_large_pte(*sptep)) {
rmap_remove(vcpu->kvm, sptep);