linux-kernel - Re: [PATCH v4 04/15] KVM: SVM: Update max number of vCPUs supported for x2AVIC mode

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Message-ID: <ffa7d6ad-56ad-9da8-ebf6-3a10d56842db@amd.com>
Date:   Mon, 9 May 2022 15:35:24 +0200
From:   "Gupta, Pankaj" <pankaj.gupta@....com>
To:     Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     pbonzini@...hat.com, mlevitsk@...hat.com, seanjc@...gle.com,
        joro@...tes.org, jon.grimm@....com, wei.huang2@....com,
        terry.bowman@....com
Subject: Re: [PATCH v4 04/15] KVM: SVM: Update max number of vCPUs supported
 for x2AVIC mode


> xAVIC and x2AVIC modes can support diffferent number of vcpus.
> Update existing logics to support each mode accordingly.
> 
> Also, modify the maximum physical APIC ID for AVIC to 255 to reflect
> the actual value supported by the architecture.
> 
> Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> ---
>   arch/x86/include/asm/svm.h | 12 +++++++++---
>   arch/x86/kvm/svm/avic.c    |  8 +++++---
>   2 files changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
> index 2c2a104b777e..4c26b0d47d76 100644
> --- a/arch/x86/include/asm/svm.h
> +++ b/arch/x86/include/asm/svm.h
> @@ -258,10 +258,16 @@ enum avic_ipi_failure_cause {
>   
>   
>   /*
> - * 0xff is broadcast, so the max index allowed for physical APIC ID
> - * table is 0xfe.  APIC IDs above 0xff are reserved.
> + * For AVIC, the max index allowed for physical APIC ID
> + * table is 0xff (255).
>    */
> -#define AVIC_MAX_PHYSICAL_ID_COUNT	0xff
> +#define AVIC_MAX_PHYSICAL_ID		0XFEULL
> +
> +/*
> + * For x2AVIC, the max index allowed for physical APIC ID
> + * table is 0x1ff (511).
> + */
> +#define X2AVIC_MAX_PHYSICAL_ID		0x1FFUL
>   
>   #define AVIC_HPA_MASK	~((0xFFFULL << 52) | 0xFFF)
>   #define VMCB_AVIC_APIC_BAR_MASK		0xFFFFFFFFFF000ULL
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index 95006bbdf970..29665b3e4e4e 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -185,7 +185,7 @@ void avic_init_vmcb(struct vcpu_svm *svm, struct vmcb *vmcb)
>   	vmcb->control.avic_backing_page = bpa & AVIC_HPA_MASK;
>   	vmcb->control.avic_logical_id = lpa & AVIC_HPA_MASK;
>   	vmcb->control.avic_physical_id = ppa & AVIC_HPA_MASK;
> -	vmcb->control.avic_physical_id |= AVIC_MAX_PHYSICAL_ID_COUNT;
> +	vmcb->control.avic_physical_id |= AVIC_MAX_PHYSICAL_ID;
>   	vmcb->control.avic_vapic_bar = APIC_DEFAULT_PHYS_BASE & VMCB_AVIC_APIC_BAR_MASK;
>   
>   	if (kvm_apicv_activated(svm->vcpu.kvm))
> @@ -200,7 +200,8 @@ static u64 *avic_get_physical_id_entry(struct kvm_vcpu *vcpu,
>   	u64 *avic_physical_id_table;
>   	struct kvm_svm *kvm_svm = to_kvm_svm(vcpu->kvm);
>   
> -	if (index >= AVIC_MAX_PHYSICAL_ID_COUNT)
> +	if ((avic_mode == AVIC_MODE_X1 && index > AVIC_MAX_PHYSICAL_ID) ||
> +	    (avic_mode == AVIC_MODE_X2 && index > X2AVIC_MAX_PHYSICAL_ID))
>   		return NULL;
>   
>   	avic_physical_id_table = page_address(kvm_svm->avic_physical_id_table_page);
> @@ -247,7 +248,8 @@ static int avic_init_backing_page(struct kvm_vcpu *vcpu)
>   	int id = vcpu->vcpu_id;
>   	struct vcpu_svm *svm = to_svm(vcpu);
>   
> -	if (id >= AVIC_MAX_PHYSICAL_ID_COUNT)
> +	if ((avic_mode == AVIC_MODE_X1 && id > AVIC_MAX_PHYSICAL_ID) ||
> +	    (avic_mode == AVIC_MODE_X2 && id > X2AVIC_MAX_PHYSICAL_ID))
>   		return -EINVAL;
>   
>   	if (!vcpu->arch.apic->regs)

Looks good to me.

Reviewed-by: Pankaj Gupta <pankaj.gupta@....com>