linux-kernel - Re: [PATCH 14/67] KVM: SVM: Add helper to deduplicate code for getting AVIC backing page

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Message-ID: <2cc31ce5-0f1a-41d6-a169-491f9712ffdc@amd.com>
Date: Tue, 15 Apr 2025 16:41:35 +0530
From: Sairaj Kodilkar <sarunkod@....com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
	<pbonzini@...hat.com>, Joerg Roedel <joro@...tes.org>, David Woodhouse
	<dwmw2@...radead.org>, Lu Baolu <baolu.lu@...ux.intel.com>
CC: <kvm@...r.kernel.org>, <iommu@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, Maxim Levitsky <mlevitsk@...hat.com>, Joao
 Martins <joao.m.martins@...cle.com>, David Matlack <dmatlack@...gle.com>
Subject: Re: [PATCH 14/67] KVM: SVM: Add helper to deduplicate code for
 getting AVIC backing page

On 4/5/2025 1:08 AM, Sean Christopherson wrote:
Hi Sean,

> Add a helper to get the physical address of the AVIC backing page, both
> to deduplicate code and to prepare for getting the address directly from
> apic->regs, at which point it won't be all that obvious that the address
> in question is what SVM calls the AVIC backing page.
> 
> No functional change intended.
> 
> Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>   arch/x86/kvm/svm/avic.c | 14 +++++++++-----
>   1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index f04010f66595..a1f4a08d35f5 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -243,14 +243,18 @@ int avic_vm_init(struct kvm *kvm)
>   	return err;
>   }
>   
> +static phys_addr_t avic_get_backing_page_address(struct vcpu_svm *svm)
> +{
> +	return __sme_set(page_to_phys(svm->avic_backing_page));
> +}
> +

Maybe why not introduce a generic function like...

static phsys_addr_t page_to_phys_sme_set(struct page *page)
{
	return __sme_set(page_to_phys(page));
}

and use it for avic_logical_id_table_page and
avic_physical_id_table_page as well.
		
Regards
Sairaj
>   void avic_init_vmcb(struct vcpu_svm *svm, struct vmcb *vmcb)
>   {
>   	struct kvm_svm *kvm_svm = to_kvm_svm(svm->vcpu.kvm);
> -	phys_addr_t bpa = __sme_set(page_to_phys(svm->avic_backing_page));
>   	phys_addr_t lpa = __sme_set(page_to_phys(kvm_svm->avic_logical_id_table_page));
>   	phys_addr_t ppa = __sme_set(page_to_phys(kvm_svm->avic_physical_id_table_page));
>   
> -	vmcb->control.avic_backing_page = bpa;
> +	vmcb->control.avic_backing_page = avic_get_backing_page_address(svm);
>   	vmcb->control.avic_logical_id = lpa;
>   	vmcb->control.avic_physical_id = ppa;
>   	vmcb->control.avic_vapic_bar = APIC_DEFAULT_PHYS_BASE;
> @@ -314,7 +318,7 @@ static int avic_init_backing_page(struct kvm_vcpu *vcpu)
>   	BUILD_BUG_ON(__PHYSICAL_MASK_SHIFT >
>   		     fls64(AVIC_PHYSICAL_ID_ENTRY_BACKING_PAGE_MASK));
>   
> -	new_entry = __sme_set(page_to_phys(svm->avic_backing_page)) |
> +	new_entry = avic_get_backing_page_address(svm) |
>   		    AVIC_PHYSICAL_ID_ENTRY_VALID_MASK;
>   	WRITE_ONCE(*entry, new_entry);
>   
> @@ -854,7 +858,7 @@ get_pi_vcpu_info(struct kvm *kvm, struct kvm_kernel_irq_routing_entry *e,
>   	pr_debug("SVM: %s: use GA mode for irq %u\n", __func__,
>   		 irq.vector);
>   	*svm = to_svm(vcpu);
> -	vcpu_info->pi_desc_addr = __sme_set(page_to_phys((*svm)->avic_backing_page));
> +	vcpu_info->pi_desc_addr = avic_get_backing_page_address(*svm);
>   	vcpu_info->vector = irq.vector;
>   
>   	return 0;
> @@ -915,7 +919,7 @@ int avic_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
>   			enable_remapped_mode = false;
>   
>   			/* Try to enable guest_mode in IRTE */
> -			pi.base = __sme_set(page_to_phys(svm->avic_backing_page));
> +			pi.base = avic_get_backing_page_address(svm);
>   			pi.ga_tag = AVIC_GATAG(to_kvm_svm(kvm)->avic_vm_id,
>   						     svm->vcpu.vcpu_id);
>   			pi.is_guest_mode = true;