Fuad Tabba <tabba@xxxxxxxxxx> writes:
> Add support for mmap() and fault() for guest_memfd backed memory
> in the host for VMs that support in-place conversion between
> shared and private. To that end, this patch adds the ability to
> check whether the VM type supports in-place conversion, and only
> allows mapping its memory if that's the case.
>
> Also add the KVM capability KVM_CAP_GMEM_SHARED_MEM, which
> indicates that the VM supports shared memory in guest_memfd, or
> that the host can create VMs that support shared memory.
> Supporting shared memory implies that memory can be mapped when
> shared with the host.
>
> This is controlled by the KVM_GMEM_SHARED_MEM configuration
> option.
>
> Signed-off-by: Fuad Tabba <tabba@xxxxxxxxxx>
> ---
> include/linux/kvm_host.h | 11 ++++
> include/uapi/linux/kvm.h | 1 +
> virt/kvm/guest_memfd.c | 105 +++++++++++++++++++++++++++++++++++++++
> virt/kvm/kvm_main.c | 4 ++
> 4 files changed, 121 insertions(+)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 7788e3625f6d..2d025b8ee20e 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -728,6 +728,17 @@ static inline bool kvm_arch_has_private_mem(struct kvm *kvm)
> }
> #endif
>
> +/*
> + * Arch code must define kvm_arch_gmem_supports_shared_mem if support for
> + * private memory is enabled and it supports in-place shared/private conversion.
> + */
> +#if !defined(kvm_arch_gmem_supports_shared_mem) && !IS_ENABLED(CONFIG_KVM_PRIVATE_MEM)
Is this a copypasta error? I'm wondering if this should be
!IS_ENABLED(CONFIG_KVM_GMEM_SHARED_MEM).
Also, would you consider defining a __weak function to be overridden by
different architectures, or would weak symbols not be inline-able?
> +static inline bool kvm_arch_gmem_supports_shared_mem(struct kvm *kvm)
> +{
> + return false;
> +}
> +#endif
> +
>
> <snip>
