Re: [PATCH v8 08/46] KVM: Provide generic interface for checking memory private/shared status

[Fuad Tabba]

On Fri, 19 Jun 2026 at 01:31, Ackerley Tng via B4 Relay
<devnull+ackerleytng.google.com@xxxxxxxxxx> wrote:
>
> From: Sean Christopherson <seanjc@xxxxxxxxxx>
>
> Introduce a generic kvm_mem_is_private() interface using a static call to
> determine if a GFN is private. This allows the implementation for checking
> a GFN's private/shared status to be set at runtime.
>
> In preparation for choosing implementations between a guest_memfd lookup
> and the existing VM attribute lookup, rename the existing
> VM-attribute-based check to kvm_vm_mem_is_private to emphasize that it
> looks up VM attributes.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>

(SoB fix plz)

Reviewed-by: Fuad Tabba <tabba@xxxxxxxxxx>

Cheers,
/fuad
> ---
>  include/linux/kvm_host.h | 12 +++++++++++-
>  virt/kvm/kvm_main.c      | 15 +++++++++++++++
>  2 files changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index eb26d4ea8945a..3915da2a61778 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2546,7 +2546,7 @@ bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
>  bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
>                                          struct kvm_gfn_range *range);
>
> -static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
> +static inline bool kvm_vm_mem_is_private(struct kvm *kvm, gfn_t gfn)
>  {
>         return kvm_get_vm_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE;
>  }
> @@ -2557,6 +2557,16 @@ static inline bool kvm_mem_range_is_private(struct kvm *kvm, gfn_t start,
>                                                   KVM_MEMORY_ATTRIBUTE_PRIVATE,
>                                                   KVM_MEMORY_ATTRIBUTE_PRIVATE);
>  }
> +#endif  /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
> +
> +#ifdef kvm_arch_has_private_mem
> +typedef bool (kvm_mem_is_private_t)(struct kvm *kvm, gfn_t gfn);
> +DECLARE_STATIC_CALL(__kvm_mem_is_private, kvm_mem_is_private_t);
> +
> +static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
> +{
> +       return static_call(__kvm_mem_is_private)(kvm, gfn);
> +}
>  #else
>  static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
>  {
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 6669f1477013c..8b238e461b854 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2627,6 +2627,20 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
>  }
>  #endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
>
> +#ifdef kvm_arch_has_private_mem
> +DEFINE_STATIC_CALL_RET0(__kvm_mem_is_private, kvm_mem_is_private_t);
> +EXPORT_STATIC_CALL_GPL(__kvm_mem_is_private);
> +
> +static void kvm_init_memory_attributes(void)
> +{
> +#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
> +       static_call_update(__kvm_mem_is_private, kvm_vm_mem_is_private);
> +#endif
> +}
> +#else
> +static void kvm_init_memory_attributes(void) { }
> +#endif
> +
>  struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
>  {
>         return __gfn_to_memslot(kvm_memslots(kvm), gfn);
> @@ -6528,6 +6542,7 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module)
>         kvm_preempt_ops.sched_in = kvm_sched_in;
>         kvm_preempt_ops.sched_out = kvm_sched_out;
>
> +       kvm_init_memory_attributes();
>         kvm_init_debug();
>
>         r = kvm_vfio_ops_init();
>
> --
> 2.55.0.rc0.738.g0c8ab3ebcc-goog
>
>