KVM: MMU: invalidate and flush on spte small->large page size change

Always invalidate spte and flush TLBs when changing page size, to make
sure different sized translations for the same address are never cached
in a CPU's TLB.

Currently the only case where this occurs is when a non-leaf spte pointer is
overwritten by a leaf, large spte entry. This can happen after dirty
logging is disabled on a memslot, for example.

Noticed by Andrea.

KVM-Stable-Tag
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 81563e7..6fbcb48 100644 (file)
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1870,6 +1870,8 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 
                        child = page_header(pte & PT64_BASE_ADDR_MASK);
                        mmu_page_remove_parent_pte(child, sptep);
 
                        child = page_header(pte & PT64_BASE_ADDR_MASK);
                        mmu_page_remove_parent_pte(child, sptep);

+                       __set_spte(sptep, shadow_trap_nonpresent_pte);
+                       kvm_flush_remote_tlbs(vcpu->kvm);

                } else if (pfn != spte_to_pfn(*sptep)) {
                        pgprintk("hfn old %lx new %lx\n",
                                 spte_to_pfn(*sptep), pfn);
                } else if (pfn != spte_to_pfn(*sptep)) {
                        pgprintk("hfn old %lx new %lx\n",
                                 spte_to_pfn(*sptep), pfn);