Re: [PATCH v5 08/12] xen/physinfo: encode Arm SVE vector length in arch_capabilities

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Luca,

> On 12 Apr 2023, at 11:49, Luca Fancellu <Luca.Fancellu@xxxxxxx> wrote:
> 
> When the arm platform supports SVE, advertise the feature in the
> field arch_capabilities in struct xen_sysctl_physinfo by encoding
> the SVE vector length in it.
> 
> Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Cheers
Bertrand

> ---
> Changes from v4:
> - Write arch_capabilities from arch_do_physinfo instead of using
>   stub functions (Jan)
> Changes from v3:
> - domainconfig_encode_vl is now named sve_encode_vl
> Changes from v2:
> - Remove XEN_SYSCTL_PHYSCAP_ARM_SVE_SHFT, use MASK_INSR and
>   protect with ifdef XEN_SYSCTL_PHYSCAP_ARM_SVE_MASK (Jan)
> - Use the helper function sve_arch_cap_physinfo to encode
>   the VL into physinfo arch_capabilities field.
> Changes from v1:
> - Use only arch_capabilities and some defines to encode SVE VL
>   (Bertrand, Stefano, Jan)
> Changes from RFC:
> - new patch
> ---
> xen/arch/arm/sysctl.c       | 4 ++++
> xen/include/public/sysctl.h | 4 ++++
> 2 files changed, 8 insertions(+)
> 
> diff --git a/xen/arch/arm/sysctl.c b/xen/arch/arm/sysctl.c
> index b0a78a8b10d0..e9a0661146e4 100644
> --- a/xen/arch/arm/sysctl.c
> +++ b/xen/arch/arm/sysctl.c
> @@ -11,11 +11,15 @@
> #include <xen/lib.h>
> #include <xen/errno.h>
> #include <xen/hypercall.h>
> +#include <asm/arm64/sve.h>
> #include <public/sysctl.h>
> 
> void arch_do_physinfo(struct xen_sysctl_physinfo *pi)
> {
>     pi->capabilities |= XEN_SYSCTL_PHYSCAP_hvm | XEN_SYSCTL_PHYSCAP_hap;
> +
> +    pi->arch_capabilities |= MASK_INSR(sve_encode_vl(get_sys_vl_len()),
> +                                       XEN_SYSCTL_PHYSCAP_ARM_SVE_MASK);
> }
> 
> long arch_do_sysctl(struct xen_sysctl *sysctl,
> diff --git a/xen/include/public/sysctl.h b/xen/include/public/sysctl.h
> index 2b24d6bfd00e..9d06e92d0f6a 100644
> --- a/xen/include/public/sysctl.h
> +++ b/xen/include/public/sysctl.h
> @@ -94,6 +94,10 @@ struct xen_sysctl_tbuf_op {
> /* Max XEN_SYSCTL_PHYSCAP_* constant.  Used for ABI checking. */
> #define XEN_SYSCTL_PHYSCAP_MAX XEN_SYSCTL_PHYSCAP_gnttab_v2
> 
> +#if defined(__arm__) || defined(__aarch64__)
> +#define XEN_SYSCTL_PHYSCAP_ARM_SVE_MASK  (0x1FU)
> +#endif
> +
> struct xen_sysctl_physinfo {
>     uint32_t threads_per_core;
>     uint32_t cores_per_socket;
> -- 
> 2.34.1
>