Re: [PATCH 08/12] KVM: remove kvm_arch_gmem_prepare_needed()

Michael Roth
2024-07-17T21:54:43Z

On Thu, Jul 11, 2024 at 06:27:51PM -0400, Paolo Bonzini wrote:
> It is enough to return 0 if a guest need not do any preparation.
> This is in fact how sev_gmem_prepare() works for non-SNP guests,
> and it extends naturally to Intel hosts: the x86 callback for
> gmem_prepare is optional and returns 0 if not defined.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/x86/kvm/x86.c | 5 -----
> include/linux/kvm_host.h | 1 -
> virt/kvm/guest_memfd.c | 13 +++----------
> 3 files changed, 3 insertions(+), 16 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index a1c85591f92c..4f58423c6148 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -13604,11 +13604,6 @@ bool kvm_arch_no_poll(struct kvm_vcpu *vcpu)
> EXPORT_SYMBOL_GPL(kvm_arch_no_poll);
>
> #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE
> -bool kvm_arch_gmem_prepare_needed(struct kvm *kvm)
> -{
> - return kvm->arch.vm_type == KVM_X86_SNP_VM;
> -}
> -
> int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, int max_order)
> {
> return static_call(kvm_x86_gmem_prepare)(kvm, pfn, gfn, max_order);
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index eb8404e9aa03..f6e11991442d 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2443,7 +2443,6 @@ static inline int kvm_gmem_get_pfn(struct kvm *kvm,
>
> #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE
> int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, int max_order);
> -bool kvm_arch_gmem_prepare_needed(struct kvm *kvm);
> #endif
>
> /**
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index f4d82719ec19..509360eefea5 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -29,16 +29,9 @@ static int __kvm_gmem_prepare_folio(struct kvm *kvm, struct kvm_memory_slot *slo
> pgoff_t index, struct folio *folio)
> {
> #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE
> - kvm_pfn_t pfn;
> - gfn_t gfn;
> - int rc;
> -
> - if (!kvm_arch_gmem_prepare_needed(kvm))
> - return 0;
> -
> - pfn = folio_file_pfn(folio, index);
> - gfn = slot->base_gfn + index - slot->gmem.pgoff;
> - rc = kvm_arch_gmem_prepare(kvm, gfn, pfn, folio_order(folio));
> + kvm_pfn_t pfn = folio_file_pfn(folio, index);
> + gfn_t gfn = slot->base_gfn + index - slot->gmem.pgoff;
> + int rc = kvm_arch_gmem_prepare(kvm, gfn, pfn, folio_order(folio));

Looks like this hunk was meant to be part of a different patch.

Otherwise:

Reviewed-by: Michael Roth <michael.roth@amd.com>

-Mike

> if (rc) {
> pr_warn_ratelimited("gmem: Failed to prepare folio for index %lx GFN %llx PFN %llx error %d.\n",
> index, gfn, pfn, rc);
> --
> 2.43.0
>
>
>