linux-kernel - [PATCH 1/4] KVM: x86: determine if an exception has an error code only when injecting it.

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Date:   Thu, 25 Feb 2021 17:41:32 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Ingo Molnar <mingo@...hat.com>,
        linux-kernel@...r.kernel.org (open list:X86 ARCHITECTURE (32-BIT AND
        64-BIT)), Jim Mattson <jmattson@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        Joerg Roedel <joro@...tes.org>, Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Wanpeng Li <wanpengli@...cent.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 1/4] KVM: x86: determine if an exception has an error code only when injecting it.

A page fault can be queued while vCPU is in real paged mode on AMD, and
AMD manual asks the user to always intercept it
(otherwise result is undefined).
The resulting VM exit, does have an error code.

Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/x86.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9fa0c7ff6e2fb..a9d814a0b5e4f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -544,8 +544,6 @@ static void kvm_multiple_exception(struct kvm_vcpu *vcpu,
 
 	if (!vcpu->arch.exception.pending && !vcpu->arch.exception.injected) {
 	queue:
-		if (has_error && !is_protmode(vcpu))
-			has_error = false;
 		if (reinject) {
 			/*
 			 * On vmentry, vcpu->arch.exception.pending is only
@@ -8345,6 +8343,13 @@ static void update_cr8_intercept(struct kvm_vcpu *vcpu)
 	static_call(kvm_x86_update_cr8_intercept)(vcpu, tpr, max_irr);
 }
 
+static void kvm_inject_exception(struct kvm_vcpu *vcpu)
+{
+	if (vcpu->arch.exception.error_code && !is_protmode(vcpu))
+		vcpu->arch.exception.error_code = false;
+	static_call(kvm_x86_queue_exception)(vcpu);
+}
+
 static void inject_pending_event(struct kvm_vcpu *vcpu, bool *req_immediate_exit)
 {
 	int r;
@@ -8353,7 +8358,7 @@ static void inject_pending_event(struct kvm_vcpu *vcpu, bool *req_immediate_exit
 	/* try to reinject previous events if any */
 
 	if (vcpu->arch.exception.injected) {
-		static_call(kvm_x86_queue_exception)(vcpu);
+		kvm_inject_exception(vcpu);
 		can_inject = false;
 	}
 	/*
@@ -8416,7 +8421,7 @@ static void inject_pending_event(struct kvm_vcpu *vcpu, bool *req_immediate_exit
 			}
 		}
 
-		static_call(kvm_x86_queue_exception)(vcpu);
+		kvm_inject_exception(vcpu);
 		can_inject = false;
 	}
 
-- 
2.26.2