From: Lai Jiangshan laijs@linux.alibaba.com
commit f6f6195b888c28a0b59ceb0562daff92a2be86c3 upstream.
When kvm_mmu_get_page() gets a page with unsynced children, the spt pagetable is unsynchronized with the guest pagetable. But the guest might not issue a "flush" operation on it when the pagetable entry is changed from zero or other cases. The hypervisor has the responsibility to synchronize the pagetables.
KVM behaved as above for many years, But commit 8c8560b83390 ("KVM: x86/mmu: Use KVM_REQ_TLB_FLUSH_CURRENT for MMU specific flushes") inadvertently included a line of code to change it without giving any reason in the changelog. It is clear that the commit's intention was to change KVM_REQ_TLB_FLUSH -> KVM_REQ_TLB_FLUSH_CURRENT, so we don't needlessly flush other contexts; however, one of the hunks changed a nearby KVM_REQ_MMU_SYNC instead. This patch changes it back.
Link: https://lore.kernel.org/lkml/20200320212833.3507-26-sean.j.christopherson@in... Cc: Sean Christopherson sean.j.christopherson@intel.com Cc: Vitaly Kuznetsov vkuznets@redhat.com Signed-off-by: Lai Jiangshan laijs@linux.alibaba.com Message-Id: 20200902135421.31158-1-jiangshanlai@gmail.com fixes: 8c8560b83390 ("KVM: x86/mmu: Use KVM_REQ_TLB_FLUSH_CURRENT for MMU specific flushes") Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kvm/mmu/mmu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2521,7 +2521,7 @@ static struct kvm_mmu_page *kvm_mmu_get_ }
if (sp->unsync_children) - kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); + kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
__clear_sp_write_flooding_count(sp); trace_kvm_mmu_get_page(sp, false);