linux-kernel - Re: [PATCH v11 30/35] KVM: x86: Add gmem hook for determining max NPT mapping level

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Date: Mon, 12 Feb 2024 11:50:26 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: Michael Roth <michael.roth@....com>
Cc: kvm@...r.kernel.org, linux-coco@...ts.linux.dev, linux-mm@...ck.org, 
	linux-crypto@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org, 
	tglx@...utronix.de, mingo@...hat.com, jroedel@...e.de, 
	thomas.lendacky@....com, hpa@...or.com, ardb@...nel.org, seanjc@...gle.com, 
	vkuznets@...hat.com, jmattson@...gle.com, luto@...nel.org, 
	dave.hansen@...ux.intel.com, slp@...hat.com, pgonda@...gle.com, 
	peterz@...radead.org, srinivas.pandruvada@...ux.intel.com, 
	rientjes@...gle.com, dovmurik@...ux.ibm.com, tobin@....com, bp@...en8.de, 
	vbabka@...e.cz, kirill@...temov.name, ak@...ux.intel.com, tony.luck@...el.com, 
	sathyanarayanan.kuppuswamy@...ux.intel.com, alpergun@...gle.com, 
	jarkko@...nel.org, ashish.kalra@....com, nikunj.dadhania@....com, 
	pankaj.gupta@....com, liam.merwick@...cle.com, zhi.a.wang@...el.com
Subject: Re: [PATCH v11 30/35] KVM: x86: Add gmem hook for determining max NPT
 mapping level

On Sat, Dec 30, 2023 at 6:32 PM Michael Roth <michael.roth@....com> wrote:
>         int max_order, r;
> +       u8 max_level;
>
>         if (!kvm_slot_can_be_private(fault->slot)) {
>                 kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
> @@ -4321,8 +4322,15 @@ static int kvm_faultin_pfn_private(struct kvm_vcpu *vcpu,
>                 return r;
>         }
>
> -       fault->max_level = min(kvm_max_level_for_order(max_order),
> -                              fault->max_level);
> +       max_level = kvm_max_level_for_order(max_order);
> +       r = static_call(kvm_x86_gmem_max_level)(vcpu->kvm, fault->pfn,
> +                                               fault->gfn, &max_level);

Might as well pass &fault->max_level directly to the callback, with no
change to the vendor-specific code.

I'll include the MMU part in a generic series to be the base for both
Intel TDX and AMD SEV-SNP, and will do that change.

Paolo

> +       if (r) {
> +               kvm_release_pfn_clean(fault->pfn);
> +               return r;
> +       }
> +
> +       fault->max_level = min(max_level, fault->max_level);
>         fault->map_writable = !(fault->slot->flags & KVM_MEM_READONLY);
>
>         return RET_PF_CONTINUE;
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 85f63b6842b6..5eb836b73131 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -4315,3 +4315,30 @@ void sev_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end)
>                 pfn += use_2m_update ? PTRS_PER_PMD : 1;
>         }
>  }
> +
> +int sev_gmem_max_level(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, u8 *max_level)
> +{
> +       int level, rc;
> +       bool assigned;
> +
> +       if (!sev_snp_guest(kvm))
> +               return 0;
> +
> +       rc = snp_lookup_rmpentry(pfn, &assigned, &level);
> +       if (rc) {
> +               pr_err_ratelimited("SEV: RMP entry not found: GFN %llx PFN %llx level %d error %d\n",
> +                                  gfn, pfn, level, rc);
> +               return -ENOENT;
> +       }
> +
> +       if (!assigned) {
> +               pr_err_ratelimited("SEV: RMP entry is not assigned: GFN %llx PFN %llx level %d\n",
> +                                  gfn, pfn, level);
> +               return -EINVAL;
> +       }
> +
> +       if (level < *max_level)
> +               *max_level = level;
> +
> +       return 0;
> +}
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index f26b8c2a8be4..f745022f7454 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -5067,6 +5067,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
>         .alloc_apic_backing_page = svm_alloc_apic_backing_page,
>
>         .gmem_prepare = sev_gmem_prepare,
> +       .gmem_max_level = sev_gmem_max_level,
>         .gmem_invalidate = sev_gmem_invalidate,
>  };
>
> --
> 2.25.1
>