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> -----Original Message-----
> From: Jan Beulich <jbeul...@suse.com>
> Sent: Thursday, June 12, 2025 6:42 PM
> To: Penny, Zheng <penny.zh...@amd.com>
> Cc: Huang, Ray <ray.hu...@amd.com>; Andrew Cooper
> <andrew.coop...@citrix.com>; Anthony PERARD <anthony.per...@vates.tech>;
> Orzel, Michal <michal.or...@amd.com>; Julien Grall <jul...@xen.org>; Roger Pau
> Monné <roger....@citrix.com>; Stefano Stabellini <sstabell...@kernel.org>;
> xen-
> de...@lists.xenproject.org
> Subject: Re: [PATCH v5 06/18] xen/x86: introduce "cpufreq=amd-cppc" xen
> cmdline
>
> On 27.05.2025 10:48, Penny Zheng wrote:
> > --- a/xen/arch/x86/platform_hypercall.c
> > +++ b/xen/arch/x86/platform_hypercall.c
> > @@ -94,6 +95,8 @@ static int __init handle_cpufreq_cmdline(enum
> > cpufreq_xen_opt option) {
> > int ret = 0;
> >
> > + /* Do not occupy bits reserved for public xen-pm */
> > + BUILD_BUG_ON(MASK_INSR(XEN_PROCESSOR_PM_CPPC,
> SIF_PM_MASK));
>
> This looks like an abuse of MASK_INSR(). Why not simply
>
> BUILD_BUG_ON(XEN_PROCESSOR_PM_CPPC & SIF_PM_MASK);
>
> ?
Because in SIF_PM_MASK, it's bit 8 to 15 reserved for xen-pm options,
See "
#define SIF_PM_MASK (0xFF<<8) /* reserve 1 byte for xen-pm options */
"
So I'm trying to use MASK_INSR() to do the necessary right shift (other than
using 8 directly, in case SIF_PM_MASK changes in the future...)
>
> Jan
