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> -----Original Message-----
> From: Jan Beulich <jbeul...@suse.com>
> Sent: Monday, August 25, 2025 11:02 PM
> To: Penny, Zheng <penny.zh...@amd.com>
> Cc: Huang, Ray <ray.hu...@amd.com>; Andrew Cooper
> <andrew.coop...@citrix.com>; Roger Pau Monné <roger....@citrix.com>;
> Anthony PERARD <anthony.per...@vates.tech>; Orzel, Michal
> <michal.or...@amd.com>; Julien Grall <jul...@xen.org>; Stefano Stabellini
> <sstabell...@kernel.org>; xen-devel@lists.xenproject.org
> Subject: Re: [PATCH v7 06/13] xen/cpufreq: introduce new sub-hypercall to
> propagate CPPC data
>
> On 22.08.2025 12:52, Penny Zheng wrote:
> > --- a/xen/arch/x86/x86_64/cpufreq.c
> > +++ b/xen/arch/x86/x86_64/cpufreq.c
> > @@ -54,3 +54,22 @@ int compat_set_px_pminfo(uint32_t acpi_id,
> >
> > return set_px_pminfo(acpi_id, xen_perf); }
> > +
> > +int compat_set_cppc_pminfo(unsigned int acpi_id,
> > + const struct compat_processor_cppc
> > +*cppc_data)
> > +
> > +{
> > + struct xen_processor_cppc *xen_cppc;
> > + unsigned long xlat_page_current;
> > +
> > + xlat_malloc_init(xlat_page_current);
> > +
> > + xen_cppc = xlat_malloc_array(xlat_page_current,
> > + struct xen_processor_cppc, 1);
> > + if ( unlikely(xen_cppc == NULL) )
> > + return -EFAULT;
>
> I think we want to avoid repeating the earlier mistake with using a wrong
> error code.
> It's ENOMEM or ENOSPC or some such.
>
Understood, I'll change it to -ENOMEM
> > --- a/xen/drivers/acpi/pm-op.c
> > +++ b/xen/drivers/acpi/pm-op.c
> > @@ -91,7 +91,9 @@ static int get_cpufreq_para(struct xen_sysctl_pm_op *op)
> > pmpt = processor_pminfo[op->cpuid];
> > policy = per_cpu(cpufreq_cpu_policy, op->cpuid);
> >
> > - if ( !pmpt || !pmpt->perf.states ||
> > + if ( !pmpt ||
> > + ((pmpt->init & XEN_PX_INIT) && !pmpt->perf.states) ||
> > + ((pmpt->init & XEN_CPPC_INIT) && pmpt->perf.state_count) ||
>
> I fear I don't understand this: In the PX case we check whether necessary
> data is
> lacking. In the CPPC case you check that some data was provided that we don't
> want to use? Why not similarly check that data we need was provided?
>
We are introducing another checking line for CPPC is actually to avoid NULL
deref of state[i]:
```
for ( i = 0; i < op->u.get_para.freq_num; i++ )
data[i] = pmpt->perf.states[i].core_frequency * 1000;
```
We want to ensure "op->u.get_para.freq_num" is always zero in CPPC mode, which
is validated against pmpt->perf.state_count.
We have similar discussion in here
https://old-list-archives.xen.org/archives/html/xen-devel/2025-06/msg01160.html
>
> Jan
