linux-kernel - Re: [PATCH 2/5] KVM: x86: Drop @vcpu parameter from kvm_x86_ops.hwapic_isr

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Message-ID: <Yqnk0dBO9ILywV3R@google.com>
Date:   Wed, 15 Jun 2022 13:55:29 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] KVM: x86: Drop @vcpu parameter from
 kvm_x86_ops.hwapic_isr_update()

On Wed, Jun 15, 2022, Paolo Bonzini wrote:
> On 6/15/22 01:05, Sean Christopherson wrote:
> > Drop the unused @vcpu parameter from hwapic_isr_update().  AMD/AVIC is
> > unlikely to implement the helper, and VMX/APICv doesn't need the vCPU as
> > it operates on the current VMCS.  The result is somewhat odd, but allows
> > for a decent amount of (future) cleanup in the APIC code.
> > 
> > No functional change intended.
> 
> Yeah, that's a bit odd; what it saves is essentially the apic->vcpu
> dereference.  I don't really like it, so if you want to have a v2 that
> passes the struct kvm_lapic* instead (which is free and keeps irr/isr
> functions consistent), I'll gladly switch.  But I _have_ queued the series
> in the meanwhile, so that's a good reason to ignore me.

I'll send a v2 and just drop the patch.  Looking at it again, it's still very odd
and I oversold the cleanup.   And the affected paths are either unlikely() or the
even slower RESET / SET_STATE flows.