linux-kernel - [PATCH] KVM: SVM: Fix build error when using -Werror=unused-but-set-variable

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Date:   Mon, 2 Oct 2023 13:28:54 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <x86@...nel.org>
CC:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] KVM: SVM: Fix build error when using -Werror=unused-but-set-variable

Commit 916e3e5f26ab ("KVM: SVM: Do not use user return MSR support for
virtualized TSC_AUX") introduced a local variable used for the rdmsr()
function for the high 32-bits of the MSR value. This variable is not used
after being set and triggers a warning or error, when treating warnings
as errors, when the unused-but-set-variable flag is set. Mark this
variable as __maybe_unused to fix this.

Fixes: 916e3e5f26ab ("KVM: SVM: Do not use user return MSR support for virtualized TSC_AUX")
Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
---
 arch/x86/kvm/svm/svm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 9507df93f410..4c917c74a4d3 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -691,7 +691,7 @@ static int svm_hardware_enable(void)
 	 */
 	if (boot_cpu_has(X86_FEATURE_V_TSC_AUX)) {
 		struct sev_es_save_area *hostsa;
-		u32 msr_hi;
+		u32 __maybe_unused msr_hi;
 
 		hostsa = (struct sev_es_save_area *)(page_address(sd->save_area) + 0x400);
 
-- 
2.41.0