Re: [PATCH v5 2/7] KVM: guest_memfd: Rename invalidate() arch hook to reclaim() and isolate it

[Xiaoyao Li]

On 7/15/2026 7:10 AM, Sean Christopherson wrote:
> Rename guest_memfd's invalidate() hook to reclaim() and isolate it via its
> own RECLAIM Kconfig, as the hook is called when a folio is freed, which is
> far too late and lacks sufficient information for KVM to actually
> invalidate its usage of the memory.  E.g. SNP uses the hook to convert
> memory back to SHARED so that it can be safely accessed by the host, there
> is no invalidation of guest mappings anywhere.  Isolating the hook will
> also allow pKVM on arm64 to opt-in to reclaim() without also having to
> differentiate between reclaim and conversions to shared for active VMs.
>
> Keep guest_memfd's trampoline, even though it would be trivial to wire up
> .free_folio() directly to an arch callback, to avoid bleeding guest_memfd
> internals into arch code (specifically, avoid referencing folios in arch
> code).
>
> Leave the kvm_x86_ops hook as-is for the moment, as the hook can be dropped
> entirely ("reclaim" on SNP is the same as convert-to-shared).
>
> Cc: Fuad Tabba <tabba@xxxxxxxxxx>
> Cc: Ackerley Tng <ackerleytng@xxxxxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
>   arch/x86/kvm/Kconfig     | 1 +
>   arch/x86/kvm/x86.c       | 7 +++++--
>   include/linux/kvm_host.h | 5 ++++-
>   virt/kvm/Kconfig         | 4 ++++
>   virt/kvm/guest_memfd.c   | 8 ++++----
>   5 files changed, 18 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> index 801bf9e520db..e0e7ad015839 100644
> --- a/arch/x86/kvm/Kconfig
> +++ b/arch/x86/kvm/Kconfig
> @@ -161,6 +161,7 @@ config KVM_AMD_SEV
>   	select ARCH_HAS_CC_PLATFORM
>   	select KVM_GENERIC_MEMORY_ATTRIBUTES
>   	select HAVE_KVM_ARCH_GMEM_PREPARE
> +	select HAVE_KVM_ARCH_GMEM_RECLAIM
>   	select HAVE_KVM_ARCH_GMEM_INVALIDATE
>   	select HAVE_KVM_ARCH_GMEM_POPULATE
>   	help
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index a2cbf6fae118..08d24c6fffa4 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10626,11 +10626,14 @@ int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, int max_ord
>   }
>   #endif
>   
> -#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE
> -void kvm_arch_gmem_invalidate(kvm_pfn_t pfn, kvm_pfn_t nr_pages, int max_order)
> +#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_RECLAIM
> +void kvm_arch_gmem_reclaim(kvm_pfn_t pfn, kvm_pfn_t nr_pages, int max_order)

The kvm_pfn_t for nr_pages still catches my eye, but it's not the 
business of this patch.

Reviewed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>