linux-kernel - Re: [EARLY RFC] KVM: SVM: Enable AVIC by default from Zen 4

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Message-ID: <aKUOtQvIAN5FC0MC@google.com>
Date: Tue, 19 Aug 2025 16:54:29 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
Cc: Naveen N Rao <naveen@...nel.org>, mlevitsk@...hat.com, 
	Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Vasant Hegde <vasant.hegde@....com>, 
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: Re: [EARLY RFC] KVM: SVM: Enable AVIC by default from Zen 4

On Tue, Aug 19, 2025, Maciej S. Szmigiero wrote:
> On 18.07.2025 10:19, Naveen N Rao wrote:
> As you can see, currently AVIC works there even without force_avic=1 so why
> now hide it behind that parameter if errata #1235 is supposedly not present
> on Zen3?

Yeah, I'm aligned with keeping the current semantics for force_avic (and by
extension for avic), and I'm pretty sure Naveen is as well.

> Also, this platform is apparently confident enough that the AVIC silicon is
> working correctly there to expose it in CPUID - maybe because that's CPU
> stepping 2 instead of the initial 0?

My vote is still to only enable AVIC by default for Zen4+.  The story for Zen3
and earlier is just too messy.