linux-kernel - [PATCH v2] KVM: SVM: Fix an off-by-one typo in the comment for enabling AVIC by default

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Message-ID: <20260109035037.1015073-1-seanjc@google.com>
Date: Thu,  8 Jan 2026 19:50:37 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Naveen N Rao <naveen@...nel.org>
Subject: [PATCH v2] KVM: SVM: Fix an off-by-one typo in the comment for
 enabling AVIC by default

Fix a goof in the comment that documents KVM's logic for enabling AVIC by
default to reference Zen5+ as family 0x1A (Zen5), not family 0x19 (Zen4).
The code is correct (checks for _greater_ than 0x19), only the comment is
flawed.

Opportunistically tweak the check too, even though it's already correct,
so that both the comment and the code reference 0x1A, and so that the
checks are "ascending", i.e. check Zen4 and then Zen5+.

No functional change intended.

Fixes: ca2967de5a5b ("KVM: SVM: Enable AVIC by default for Zen4+ if x2AVIC is support")
Acked-by: Naveen N Rao (AMD) <naveen@...nel.org>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---

v2: Update the code to precisely match the comment. [Naveen]

v1: https://lore.kernel.org/all/20260107204546.570403-1-seanjc@google.com

 arch/x86/kvm/svm/avic.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 6b77b2033208..e8acac56da5b 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -1224,13 +1224,13 @@ static bool __init avic_want_avic_enabled(void)
 	 * In "auto" mode, enable AVIC by default for Zen4+ if x2AVIC is
 	 * supported (to avoid enabling partial support by default, and because
 	 * x2AVIC should be supported by all Zen4+ CPUs).  Explicitly check for
-	 * family 0x19 and later (Zen5+), as the kernel's synthetic ZenX flags
+	 * family 0x1A and later (Zen5+), as the kernel's synthetic ZenX flags
 	 * aren't inclusive of previous generations, i.e. the kernel will set
 	 * at most one ZenX feature flag.
 	 */
 	if (avic == AVIC_AUTO_MODE)
 		avic = boot_cpu_has(X86_FEATURE_X2AVIC) &&
-		       (boot_cpu_data.x86 > 0x19 || cpu_feature_enabled(X86_FEATURE_ZEN4));
+		       (cpu_feature_enabled(X86_FEATURE_ZEN4) || boot_cpu_data.x86 >= 0x1A);
 
 	if (!avic || !npt_enabled)
 		return false;

base-commit: 9448598b22c50c8a5bb77a9103e2d49f134c9578
-- 
2.52.0.457.g6b5491de43-goog