linux-kernel - [PATCH 1/2] KVM: x86: Return emulator error if RDMSR/WRMSR emulation failed

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Date:   Thu, 28 Jul 2022 16:25:04 +0800
From:   "Hou Wenlong" <houwenlong.hwl@...group.com>
To:     kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] KVM: x86: Return emulator error if RDMSR/WRMSR emulation failed

The return value of emulator_{get|set}_mst_with_filter()
is confused, since msr access error and emulator error
are mixed. Although, KVM_MSR_RET_* doesn't conflict with
X86EMUL_IO_NEEDED at present, it is better to convert
msr access error to emulator error if error value is
needed.

Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
---
 arch/x86/kvm/x86.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5366f884e9a7..8df89b9c212f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7908,11 +7908,12 @@ static int emulator_get_msr_with_filter(struct x86_emulate_ctxt *ctxt,
 	int r;
 
 	r = kvm_get_msr_with_filter(vcpu, msr_index, pdata);
-
-	if (r && kvm_msr_user_space(vcpu, msr_index, KVM_EXIT_X86_RDMSR, 0,
-				    complete_emulated_rdmsr, r)) {
-		/* Bounce to user space */
-		return X86EMUL_IO_NEEDED;
+	if (r) {
+		if (kvm_msr_user_space(vcpu, msr_index, KVM_EXIT_X86_RDMSR, 0,
+				       complete_emulated_rdmsr, r))
+			r = X86EMUL_IO_NEEDED;
+		else
+			r = X86EMUL_UNHANDLEABLE;
 	}
 
 	return r;
@@ -7925,11 +7926,12 @@ static int emulator_set_msr_with_filter(struct x86_emulate_ctxt *ctxt,
 	int r;
 
 	r = kvm_set_msr_with_filter(vcpu, msr_index, data);
-
-	if (r && kvm_msr_user_space(vcpu, msr_index, KVM_EXIT_X86_WRMSR, data,
-				    complete_emulated_msr_access, r)) {
-		/* Bounce to user space */
-		return X86EMUL_IO_NEEDED;
+	if (r > 0) {
+		if (kvm_msr_user_space(vcpu, msr_index, KVM_EXIT_X86_WRMSR, data,
+				       complete_emulated_msr_access, r))
+			r = X86EMUL_IO_NEEDED;
+		else
+			r = X86EMUL_UNHANDLEABLE;
 	}
 
 	return r;
-- 
2.31.1