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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Date:   Wed, 31 Aug 2022 09:09:06 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     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, 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.

Best regards,
	Maxim Levitsky