From: Sean Christopherson <seanjc@google.com>
To: "Naveen N Rao (AMD)" <naveen@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, Jim Mattson <jmattson@google.com>,
Maxim Levitsky <mlevitsk@redhat.com>,
Vasant Hegde <vasant.hegde@amd.com>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
Nikunj A Dadhania <nikunj@amd.com>,
Alejandro Jimenez <alejandro.j.jimenez@oracle.com>,
Joao Martins <joao.m.martins@oracle.com>,
"Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>
Subject: Re: [RFC PATCH v2 5/5] KVM: SVM: Enable AVIC by default from Zen 4
Date: Mon, 15 Sep 2025 16:17:05 -0700 [thread overview]
Message-ID: <aMiecWn8kZFXjNZ9@google.com> (raw)
In-Reply-To: <46b11506a6cf566fd55d3427020c0efea13bfc6a.1756993734.git.naveen@kernel.org>
On Thu, Sep 04, 2025, Naveen N Rao (AMD) wrote:
> + /* Enable AVIC by default from Zen 4 */
> + if (default_avic)
> + avic = boot_cpu_data.x86 > 0x19 || cpu_feature_enabled(X86_FEATURE_ZEN4);
Got distracted and forgot to respond the actual code. This needs a comment,
because intuitively I expected Zen4 to be inclusive of Zen5 and beyond, i.e. the
model check confused me. But the kernel's ZenX flags are one-off things.
I also think we should enabled AVIC by default if and only if x2AVIC is supported,
because Zen4+ should all have x2AVIC, and I don't want to incorrectly suggest that
AVIC is fully enabled when in fact the only aspect of AVIC that would be utilized
is KVM's use of the doorbell to deliver interrupts.
> +
> if (!avic || !npt_enabled)
> goto out;
>
next prev parent reply other threads:[~2025-09-15 23:17 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-04 18:00 [RFC PATCH v2 0/5] KVM: SVM: Enable AVIC by default on Zen 4+ Naveen N Rao (AMD)
2025-09-04 18:00 ` [RFC PATCH v2 1/5] KVM: SVM: Stop warning if x2AVIC feature bit alone is enabled Naveen N Rao (AMD)
2025-09-15 20:04 ` Sean Christopherson
2025-09-16 7:14 ` Naveen N Rao
2025-09-16 13:40 ` Mario Limonciello
2025-09-16 13:51 ` Sean Christopherson
2025-09-16 18:37 ` Naveen N Rao
2025-09-16 19:26 ` Mario Limonciello
2025-09-17 0:44 ` Sean Christopherson
2025-09-04 18:00 ` [RFC PATCH v2 2/5] KVM: SVM: Simplify the message printed with 'force_avic' Naveen N Rao (AMD)
2025-09-15 22:42 ` Sean Christopherson
2025-09-04 18:00 ` [RFC PATCH v2 3/5] KVM: SVM: Move all AVIC setup to avic_hardware_setup() Naveen N Rao (AMD)
2025-09-15 19:59 ` Sean Christopherson
2025-09-04 18:00 ` [RFC PATCH v2 4/5] KVM: SVM: Move 'force_avic' module parameter to svm.c Naveen N Rao (AMD)
2025-09-15 22:43 ` Sean Christopherson
2025-09-04 18:00 ` [RFC PATCH v2 5/5] KVM: SVM: Enable AVIC by default from Zen 4 Naveen N Rao (AMD)
2025-09-15 22:53 ` Sean Christopherson
2025-09-16 7:39 ` Naveen N Rao
2025-09-16 14:27 ` Sean Christopherson
2025-09-16 18:53 ` Naveen N Rao
2025-09-15 23:17 ` Sean Christopherson [this message]
2025-09-16 10:17 ` Naveen N Rao
2025-09-15 23:23 ` [RFC PATCH v2 0/5] KVM: SVM: Enable AVIC by default on Zen 4+ Sean Christopherson
2025-09-16 10:31 ` Naveen N Rao
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