Re: [PATCH 21/26] kvm/memory: Make memory type private by default if it has guest memfd backend

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 3/23/2024 2:11 AM, Paolo Bonzini wrote:
> From: Xiaoyao Li <xiaoyao.li@intel.com>
> 
> KVM side leaves the memory to shared by default, while may incur the

/s/while/which/

fix typo from myself.

> overhead of paging conversion on the first visit of each page. Because
> the expectation is that page is likely to private for the VMs that
> require private memory (has guest memfd).
> 
> Explicitly set the memory to private when memory region has valid
> guest memfd backend.
> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> Message-ID: <20240320083945.991426-16-michael.roth@amd.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   accel/kvm/kvm-all.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
> 
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 7fbaf31cbaf..56b17cbd8aa 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -1430,6 +1430,16 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
>                       strerror(-err));
>               abort();
>           }
> +
> +        if (memory_region_has_guest_memfd(mr)) {
> +            err = kvm_set_memory_attributes_private(start_addr, slot_size);
> +            if (err) {
> +                error_report("%s: failed to set memory attribute private: %s\n",
> +                             __func__, strerror(-err));
> +                exit(1);
> +            }
> +        }
> +
>           start_addr += slot_size;
>           ram_start_offset += slot_size;
>           ram += slot_size;