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,
Naveen N Rao <naveen@kernel.org>
Subject: [PATCH v3 4/6] KVM: SVM: Don't advise the user to do force_avic=y (when x2AVIC is detected)
Date: Thu, 18 Sep 2025 17:21:34 -0700 [thread overview]
Message-ID: <20250919002136.1349663-5-seanjc@google.com> (raw)
In-Reply-To: <20250919002136.1349663-1-seanjc@google.com>
Don't advise the end user to try to force enable AVIC when x2AVIC is
reported as supported in CPUID, as forcefully enabling AVIC isn't something
that should be done lightly. E.g. some Zen4 client systems hide AVIC but
leave x2AVIC behind, and while such a configuration is indeed due to buggy
firmware in the sense the reporting x2AVIC without AVIC is nonsensical,
KVM has no idea _why_ firmware disabled AVIC in the first place.
Suggesting that the user try to run with force_avic=y is sketchy even if
the user explicitly tries to enable AVIC, and will be downright
irresponsible once KVM starts enabling AVIC by default. Alternatively,
KVM could print the message only when the user explicitly asks for AVIC,
but running with force_avic=y isn't something that should be encouraged
for random users. force_avic is a useful knob for developers and perhaps
even advanced users, but isn't something that KVM should advertise broadly.
Opportunistically append a newline to the pr_warn() so that it prints out
immediately, and tweak the message to say that AVIC is unsupported instead
of disabled (disabled suggests that the kernel/KVM is somehow responsible).
Suggested-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/svm/avic.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index bafef2f75af2..497d755c206f 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -1154,10 +1154,8 @@ bool __init avic_hardware_setup(struct kvm_x86_ops *svm_ops)
/* AVIC is a prerequisite for x2AVIC. */
if (!boot_cpu_has(X86_FEATURE_AVIC) && !force_avic) {
- if (boot_cpu_has(X86_FEATURE_X2AVIC)) {
- pr_warn(FW_BUG "Cannot support x2AVIC due to AVIC is disabled");
- pr_warn(FW_BUG "Try enable AVIC using force_avic option");
- }
+ if (boot_cpu_has(X86_FEATURE_X2AVIC))
+ pr_warn(FW_BUG "Cannot enable x2AVIC, AVIC is unsupported\n");
return false;
}
--
2.51.0.470.ga7dc726c21-goog
next prev parent reply other threads:[~2025-09-19 0:21 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-19 0:21 [PATCH v3 0/6] KVM: SVM: Enable AVIC for Zen4+ (if x2AVIC) Sean Christopherson
2025-09-19 0:21 ` [PATCH v3 1/6] KVM: SVM: Move x2AVIC MSR interception helper to avic.c Sean Christopherson
2025-09-19 9:35 ` Naveen N Rao
2025-09-19 0:21 ` [PATCH v3 2/6] KVM: SVM: Update "APICv in x2APIC without x2AVIC" in avic.c, not svm.c Sean Christopherson
2025-09-19 9:42 ` Naveen N Rao
2025-09-19 14:21 ` Sean Christopherson
2025-09-22 7:08 ` Chao Gao
2025-09-19 0:21 ` [PATCH v3 3/6] KVM: SVM: Always print "AVIC enabled" separately, even when force enabled Sean Christopherson
2025-09-19 9:52 ` Naveen N Rao
2025-09-19 0:21 ` Sean Christopherson [this message]
2025-09-19 10:26 ` [PATCH v3 4/6] KVM: SVM: Don't advise the user to do force_avic=y (when x2AVIC is detected) Naveen N Rao
2025-09-19 0:21 ` [PATCH v3 5/6] KVM: SVM: Move global "avic" variable to avic.c Sean Christopherson
2025-09-19 10:31 ` Naveen N Rao
2025-09-19 14:44 ` Sean Christopherson
2025-09-19 18:27 ` Naveen N Rao
2025-09-19 0:21 ` [PATCH v3 6/6] KVM: SVM: Enable AVIC by default for Zen4+ if x2AVIC is support Sean Christopherson
2025-09-19 10:37 ` Naveen N Rao
2025-09-19 21:56 ` Sean Christopherson
2025-09-19 10:42 ` [PATCH v3 0/6] KVM: SVM: Enable AVIC for Zen4+ (if x2AVIC) Naveen N Rao
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20250919002136.1349663-5-seanjc@google.com \
--to=seanjc@google.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=naveen@kernel.org \
--cc=pbonzini@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox