Re: [RFC PATCH 02/23] kvm: Switch KVM_CAP_READONLY_MEM to a per-VM ioctl()

[Philippe Mathieu-Daudé]

Hi Isaku,

On 2/16/21 3:12 AM, Isaku Yamahata wrote:
> Switch to making a VM ioctl() call for KVM_CAP_READONLY_MEM, which may
> be conditional on VM type in recent versions of KVM, e.g. when TDX is
> supported.
> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
>  accel/kvm/kvm-all.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 47516913b7..351c25a5cb 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -2164,7 +2164,7 @@ static int kvm_init(MachineState *ms)
>      }
>  
>      kvm_readonly_mem_allowed =
> -        (kvm_check_extension(s, KVM_CAP_READONLY_MEM) > 0);
> +        (kvm_vm_check_extension(s, KVM_CAP_READONLY_MEM) > 0);

Can this check with "recent KVM" be a problem with older ones?

Maybe for backward compatibility we need:

          = (kvm_vm_check_extension(s, KVM_CAP_READONLY_MEM) > 0) ||
            (kvm_check_extension(s, KVM_CAP_READONLY_MEM) > 0);

>      kvm_eventfds_allowed =
>          (kvm_check_extension(s, KVM_CAP_IOEVENTFD) > 0);
>