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From: Sean Christopherson <seanjc@google.com>
To: Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	 Borislav Petkov <bp@alien8.de>
Subject: [PATCH 3/3] KVM: SVM: Use compound literal in lieu of __maybe_unused rdmsr() param
Date: Mon, 17 Jun 2024 14:04:32 -0700	[thread overview]
Message-ID: <20240617210432.1642542-4-seanjc@google.com> (raw)
In-Reply-To: <20240617210432.1642542-1-seanjc@google.com>

When reading MSR_TSC_AUX, which is effectively a 32-bit value, use a
compound literal to consume/ignore the upper 32 bits instead of a "maybe"
unused local variable.  While (ab)using a compound literal to discard an
unused output is unusual, it's perfectly legal as compound literals are
valid, modifiable l-values in C99 and beyond.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/svm/svm.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index cf285472fea6..69c0dea5cc0d 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -678,11 +678,8 @@ static int svm_hardware_enable(void)
 	 * Since Linux does not change the value of TSC_AUX once set, prime the
 	 * TSC_AUX field now to avoid a RDMSR on every vCPU run.
 	 */
-	if (boot_cpu_has(X86_FEATURE_V_TSC_AUX)) {
-		u32 __maybe_unused msr_hi;
-
-		rdmsr(MSR_TSC_AUX, sev_es_host_save_area(sd)->tsc_aux, msr_hi);
-	}
+	if (boot_cpu_has(X86_FEATURE_V_TSC_AUX))
+		rdmsr(MSR_TSC_AUX, sev_es_host_save_area(sd)->tsc_aux, (u32){0});
 
 	return 0;
 }
-- 
2.45.2.627.g7a2c4fd464-goog


  parent reply	other threads:[~2024-06-17 21:04 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-06-17 21:04 [PATCH 0/3] KVM: SVM: SEV-ES save area fix+cleanups Sean Christopherson
2024-06-17 21:04 ` [PATCH 1/3] KVM: SVM: Force sev_es_host_save_area() to be inlined (for noinstr usage) Sean Christopherson
2024-06-18 10:17   ` Borislav Petkov
2024-06-17 21:04 ` [PATCH 2/3] KVM: SVM: Use sev_es_host_save_area() helper when initializing tsc_aux Sean Christopherson
2024-06-17 21:04 ` Sean Christopherson [this message]
2024-06-18 10:24   ` [PATCH 3/3] KVM: SVM: Use compound literal in lieu of __maybe_unused rdmsr() param Borislav Petkov
2024-06-18 13:44     ` Sean Christopherson
2024-06-18 13:49       ` Borislav Petkov
2024-06-28 22:55 ` [PATCH 0/3] KVM: SVM: SEV-ES save area fix+cleanups Sean Christopherson

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