[v2,13/17] KVM: nVMX: Defer the MMU reload to the normal path on an EPTP switch

Commit Message

Sean Christopherson March 5, 2021, 1:10 a.m. UTC

Defer reloading the MMU after a EPTP successful EPTP switch.  The VMFUNC
instruction itself is executed in the previous EPTP context, any side
effects, e.g. updating RIP, should occur in the old context.  Practically
speaking, this bug is benign as VMX doesn't touch the MMU when skipping
an emulated instruction, nor does queuing a single-step #DB.  No other
post-switch side effects exist.

Fixes: 41ab93727467 ("KVM: nVMX: Emulate EPTP switching for the L1 hypervisor")
Cc: [e-mail]
Signed-off-by: Sean Christopherson <[e-mail]>
---
 arch/x86/kvm/vmx/nested.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

Patch

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index fdd80dd8e781..81f609886c8b 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5473,16 +5473,11 @@  static int nested_vmx_eptp_switching(struct kvm_vcpu *vcpu,
 		if (!nested_vmx_check_eptp(vcpu, new_eptp))
 			return 1;
 
-		kvm_mmu_unload(vcpu);
 		mmu->ept_ad = accessed_dirty;
 		mmu->mmu_role.base.ad_disabled = !accessed_dirty;
 		vmcs12->ept_pointer = new_eptp;
-		/*
-		 * TODO: Check what's the correct approach in case
-		 * mmu reload fails. Currently, we just let the next
-		 * reload potentially fail
-		 */
-		kvm_mmu_reload(vcpu);
+
+		kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu);
 	}
 
 	return 0;