Re: [PATCH 08/16] xen/sysctl: Drop XEN_SYSCTL_get_cpu_levelling_caps

[Jan Beulich <jbeulich@xxxxxxxx>]

On 26.01.2026 18:53, Andrew Cooper wrote:
> This hypercall is an addition of mine from commit 67528a3f0649 ("x86/cpu:
> Sysctl and common infrastructure for levelling context switching", 2016), but
> it never got wired into any toolstacks.  In the meantime, how we handle CPUID
> for guests has evolved substantially.
> 
> In order to reuse the AMD levelling infrasturcture for boot time quirks,
> levelling_caps is going to have to change.  While it's probably safe to expose
> this difference, it's safer still to make it an internal detail.
> 
> When re-plummbing the LCAP_* constants, turn them all into single bits.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx> # hypervisor & ~xsm

> --- a/xen/arch/x86/include/asm/cpuid.h
> +++ b/xen/arch/x86/include/asm/cpuid.h
>[...]
>  extern unsigned int expected_levelling_cap, levelling_caps;
Observation while doing the review: Why are both _probe_mask_msr()'s
2nd parameters uint64_t, when the variables here are unsigned int?

> @@ -1270,7 +1251,7 @@ struct xen_sysctl {
>  #define XEN_SYSCTL_pcitopoinfo                   22
>  #define XEN_SYSCTL_psr_alloc                     23
>  /* #define XEN_SYSCTL_tmem_op                       24 */
> -#define XEN_SYSCTL_get_cpu_levelling_caps        25
> +/* #define XEN_SYSCTL_get_cpu_levelling_caps        25 */

I realize this it to match the earlier line, yet would you mind rather ...

>  #define XEN_SYSCTL_get_cpu_featureset            26
>  #define XEN_SYSCTL_livepatch_op                  27
>  /* #define XEN_SYSCTL_set_parameter              28 */

... following this style? (I wouldn't mind if you also touched the malformed
tmem line at the same time.)

Jan