Re: [PATCH] x86/hvm: short-circuit HVM shadow guest creation earlier

[Alejandro Vallejo]

On Mon Feb 9, 2026 at 3:40 PM CET, Roger Pau Monne wrote:
> If shadow paging has been compiled out short circuit the creation of HVM
> guests that attempt to use shadow paging at arch_sanitise_domain_config().
> There's no need to further build the domain when creation is doomed to fail
> later on.
>
> Signed-off-by: Roger Pau Monné <roger....@citrix.com>
> ---
>  xen/arch/x86/domain.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> index 8b2f33f1a06c..8eb1509782ef 100644
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -627,6 +627,12 @@ int arch_sanitise_domain_config(struct 
> xen_domctl_createdomain *config)
>          return -EINVAL;
>      }
>  
> +    if ( hvm && !hap && !IS_ENABLED(CONFIG_SHADOW_PAGING) )
> +    {
> +        dprintk(XENLOG_INFO, "Shadow paging requested but not available\n");

nit: s/requested/required/, maybe?

Also, with this in place can't we get rid of the panic in create_dom0() that
checks an identical condition?

Cheers,
Alejandro