Re: [PATCH] x86/vmx: Avoid pausing on HVM_PARAM_IDENT_PT in additional cases

["Teddy Astie" <teddy.astie@xxxxxxxxxx>]

Le 30/07/2025 à 18:40, Teddy Astie a écrit :
> When settings HVM_PARAM_IDENT_PT, skip domain pausing when :
> - there is no vcpu
> - unrestricted guest capability is used
>
> Signed-off-by: Teddy Astie <teddy.astie@xxxxxxxxxx>
> ---
>   xen/arch/x86/hvm/hvm.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index e2720daf1e..39ff1bdbe1 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -4286,11 +4286,13 @@ static int hvm_set_param(struct domain *d, uint32_t 
> index, uint64_t value)
>               rc = -EINVAL;
>           break;
>       case HVM_PARAM_IDENT_PT:
> +        v = domain_vcpu(d, 0);
> +
>           /*
>            * Only actually required for VT-x lacking unrestricted_guest
>            * capabilities.  Short circuit the pause if possible.
>            */
> -        if ( !paging_mode_hap(d) || !cpu_has_vmx )
> +        if ( !paging_mode_hap(d) || !cpu_has_vmx || !v || 
> vmx_unrestricted_guest(v) )
>           {
>               d->arch.hvm.params[index] = value;
>               break;

Although, I am not completely sure if the vcpu checks (including
vmx_unrestricted_guest one) needs to be moved after the domctl_lock_acquire.


Teddy Astie | Vates XCP-ng Developer

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