Re: [PATCH v9 07/17] KVM: guest_memfd: Allow host to map guest_memfd() pages

[Gavin Shan <gshan@redhat.com>]

Hi Fuad,

On 5/14/25 2:34 AM, Fuad Tabba wrote:
> This patch enables support for shared memory in guest_memfd, including
> mapping that memory at the host userspace. This support is gated by the
> configuration option KVM_GMEM_SHARED_MEM, and toggled by the guest_memfd
> flag GUEST_MEMFD_FLAG_SUPPORT_SHARED, which can be set when creating a
> guest_memfd instance.
> 
> Co-developed-by: Ackerley Tng <ackerleytng@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
> Signed-off-by: Fuad Tabba <tabba@google.com>
> ---
>   arch/x86/include/asm/kvm_host.h | 10 ++++
>   include/linux/kvm_host.h        | 13 +++++
>   include/uapi/linux/kvm.h        |  1 +
>   virt/kvm/Kconfig                |  5 ++
>   virt/kvm/guest_memfd.c          | 88 +++++++++++++++++++++++++++++++++
>   5 files changed, 117 insertions(+)
> 

[...]

> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index b6ae8ad8934b..9857022a0f0c 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1566,6 +1566,7 @@ struct kvm_memory_attributes {
>   #define KVM_MEMORY_ATTRIBUTE_PRIVATE           (1ULL << 3)
>   
>   #define KVM_CREATE_GUEST_MEMFD	_IOWR(KVMIO,  0xd4, struct kvm_create_guest_memfd)
> +#define GUEST_MEMFD_FLAG_SUPPORT_SHARED	(1UL << 0)
>   

This would be (1ULL << 0) to be consistent with '__u64 struct kvm_create_guest_memfd::flags'

Thanks,
Gavin