linux-kernel - Re: [PATCH 06/19] KVM: SVM: Get x2APIC logical dest bitmap from ICRH[15:0], not ICHR[31:16]

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Message-ID: <Yw+N1BdfSansWh8h@google.com>
Date:   Wed, 31 Aug 2022 16:35:32 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        Li RongQing <lirongqing@...du.com>
Subject: Re: [PATCH 06/19] KVM: SVM: Get x2APIC logical dest bitmap from
 ICRH[15:0], not ICHR[31:16]

On Wed, Aug 31, 2022, Maxim Levitsky wrote:
> On Wed, 2022-08-31 at 09:09 +0300, Maxim Levitsky wrote:
> > On Wed, 2022-08-31 at 00:34 +0000, Sean Christopherson wrote:
> > > When attempting a fast kick for x2AVIC, get the destination bitmap from
> > > ICR[15:0], not ICHR[31:16].  The upper 16 bits contain the cluster, the
> > > lower 16 bits hold the bitmap.
> > > 
> > > Fixes: 603ccef42ce9 ("KVM: x86: SVM: fix avic_kick_target_vcpus_fast")
> > > Cc: Maxim Levitsky <mlevitsk@...hat.com>
> > > Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> > > ---
> > >  arch/x86/kvm/svm/avic.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> > > index 3ace0f2f52f0..3c333cd2e752 100644
> > > --- a/arch/x86/kvm/svm/avic.c
> > > +++ b/arch/x86/kvm/svm/avic.c
> > > @@ -368,7 +368,7 @@ static int avic_kick_target_vcpus_fast(struct kvm *kvm, struct kvm_lapic *source
> > >  
> > >  		if (apic_x2apic_mode(source)) {
> > >  			/* 16 bit dest mask, 16 bit cluster id */
> > > -			bitmap = dest & 0xFFFF0000;
> > > +			bitmap = dest & 0xFFFF;
> > >  			cluster = (dest >> 16) << 4;
> > >  		} else if (kvm_lapic_get_reg(source, APIC_DFR) == APIC_DFR_FLAT) {
> > >  			/* 8 bit dest mask*/
> > 
> > I swear I have seen a patch from Suravee Suthikulpanit fixing this my mistake, I don't know why it was not
> > accepted upstream.
> 
> This is the patch, which I guess got forgotten.
> 
> https://www.spinics.net/lists/kernel/msg4417427.html

Ah, we just missed it, doubt there's anything more than that to the story.

> Since it is literaly the same patch, you can just add credit to Suravee Suthikulpanit.
> 
> So with the credit added:
> 
> Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>

I'll grab Suravee's patch and added your review.  Thanks!