From b119019847fbcac36ed1384f166c91f177d070e7 Mon Sep 17 00:00:00 2001 From: Jim Mattson Date: Thu, 13 Jun 2019 09:16:08 -0700 Subject: [PATCH] kvm: nVMX: Remove unnecessary sync_roots from handle_invept When L0 is executing handle_invept(), the TDP MMU is active. Emulating an L1 INVEPT does require synchronizing the appropriate shadow EPT root(s), but a call to kvm_mmu_sync_roots in this context won't do that. Similarly, the hardware TLB and paging-structure-cache entries associated with the appropriate shadow EPT root(s) must be flushed, but requesting a TLB_FLUSH from this context won't do that either. How did this ever work? KVM always does a sync_roots and TLB flush (in the correct context) when transitioning from L1 to L2. That isn't the best choice for nested VM performance, but it effectively papers over the mistakes here. Remove the unnecessary operations and leave a comment to try to do better in the future. Reported-by: Junaid Shahid Fixes: bfd0a56b90005f ("nEPT: Nested INVEPT") Cc: Xiao Guangrong Cc: Nadav Har'El Cc: Jun Nakajima Cc: Xinhao Xu Cc: Yang Zhang Cc: Gleb Natapov Cc: Paolo Bonzini Reviewed-by Peter Shier Reviewed-by: Junaid Shahid Signed-off-by: Jim Mattson Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/nested.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 509841916d23..118d185764ec 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -4835,13 +4835,11 @@ static int handle_invept(struct kvm_vcpu *vcpu) switch (type) { case VMX_EPT_EXTENT_GLOBAL: + case VMX_EPT_EXTENT_CONTEXT: /* - * TODO: track mappings and invalidate - * single context requests appropriately + * TODO: Sync the necessary shadow EPT roots here, rather than + * at the next emulated VM-entry. */ - case VMX_EPT_EXTENT_CONTEXT: - kvm_mmu_sync_roots(vcpu); - kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu); break; default: BUG_ON(1); -- 2.11.0