linux-kernel - [PATCH] KVM: nSVM: remove nonsensical EXITINFO1 adjustment on nested NPF

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Date:   Fri, 10 Jul 2020 16:51:06 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Nadav Amit <namit@...are.com>
Subject: [PATCH] KVM: nSVM: remove nonsensical EXITINFO1 adjustment on nested NPF

The "if" that drops the present bit from the page structure fauls makes no sense.
It was added by yours truly in order to be bug-compatible with pre-existing code
and in order to make the tests pass; however, the tests are wrong.  The behavior
after this patch matches bare metal.

Reported-by: Nadav Amit <namit@...are.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/svm/nested.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 7b331e3da3eb..61378a3c2ce4 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -48,13 +48,6 @@ static void nested_svm_inject_npf_exit(struct kvm_vcpu *vcpu,
 	svm->vmcb->control.exit_info_1 &= ~0xffffffffULL;
 	svm->vmcb->control.exit_info_1 |= fault->error_code;
 
-	/*
-	 * The present bit is always zero for page structure faults on real
-	 * hardware.
-	 */
-	if (svm->vmcb->control.exit_info_1 & (2ULL << 32))
-		svm->vmcb->control.exit_info_1 &= ~1;
-
 	nested_svm_vmexit(svm);
 }
 
-- 
2.26.2