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

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Message-ID: <Z_5z0an7-BJ1bTzF@google.com>
Date: Tue, 15 Apr 2025 07:57:21 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sairaj Kodilkar <sarunkod@....com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Joerg Roedel <joro@...tes.org>, 
	David Woodhouse <dwmw2@...radead.org>, Lu Baolu <baolu.lu@...ux.intel.com>, 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 Tue, Apr 15, 2025, Sairaj Kodilkar wrote:
> 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.

Because subsequent commits remove the "struct page" tracking (it's suboptimal
and confusing), and I don't want to encourage that bad pattern in the future.