Re: [PATCH v3 2/6] ARM/sysctl: Expose the supported guest GIC modes in physinfo

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 16/07/2026 3:11 pm, Julian Vetter wrote:
> From: Andrew Cooper <andrew.cooper3@citrix.com>

I supposed I should finish the commit message.

"In preparation to simplify the domain creation logic surrounding GIC
version."


> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> ---
> Changes in v3:
> - No changes
> ---
>  xen/arch/arm/sysctl.c       | 26 ++++++++++++++++++++++++++
>  xen/include/public/sysctl.h |  2 ++
>  2 files changed, 28 insertions(+)
>
> diff --git a/xen/arch/arm/sysctl.c b/xen/arch/arm/sysctl.c
> index 32cab4feff..3b0edf4cec 100644
> --- a/xen/arch/arm/sysctl.c
> +++ b/xen/arch/arm/sysctl.c
> @@ -12,7 +12,10 @@
>  #include <xen/dt-overlay.h>
>  #include <xen/errno.h>
>  #include <xen/hypercall.h>
> +
>  #include <asm/arm64/sve.h>
> +#include <asm/gic.h>
> +
>  #include <public/sysctl.h>
>  
>  void arch_do_physinfo(struct xen_sysctl_physinfo *pi)
> @@ -21,6 +24,29 @@ void arch_do_physinfo(struct xen_sysctl_physinfo *pi)
>  
>      pi->arch_capabilities |= MASK_INSR(sve_encode_vl(get_sys_vl_len()),
>                                         XEN_SYSCTL_PHYSCAP_ARM_SVE_MASK);
> +
> +    /*
> +     * The GIC version(s) we're happy creating guests with.  Right now for
> +     * simplicity it is tied to the active hardware version, but this will
> +     * cease to be the case if/when the compatbility modes are enabled.
> +     */
> +    switch ( gic_hw_version() )
> +    {
> +    case GIC_V2:
> +        pi->arch_capabilities |= XEN_SYSCTL_PHYSCAP_ARM_GIC_V2;
> +        break;
> +
> +    case GIC_V3:
> +        pi->arch_capabilities |= XEN_SYSCTL_PHYSCAP_ARM_GIC_V3;
> +        break;
> +
> +    case GIC_INVALID:
> +        /*
> +         * Running a control domain without having the GIC sorted yet?
> +         * Something's broken, but there's nothing we can do about it here.
> +         */

printk_once(XENLOG_ERR "Unrecognised GIC version %d\n", gic_ver);

We might not be able to do anything useful for the caller, but we can at
least make sure the problem doesn't go unnoticed.

~Andrew