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Re: [PATCH v3 07/15] xen/cpufreq: fix core frequency calculation for AMD Family 1Ah CPUs
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
- Date: Tue, 25 Mar 2025 11:55:53 +0100
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- Cc: Penny Zheng <Penny.Zheng@xxxxxxx>, ray.huang@xxxxxxx, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Tue, 25 Mar 2025 10:55:57 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 2025-03-24 16:47, Jan Beulich wrote:
On 06.03.2025 09:39, Penny Zheng wrote:
This commit fixes core frequency calculation for AMD Family 1Ah CPUs,
due to
a change in the PStateDef MSR layout in AMD Family 1Ah+.
In AMD Family 1Ah+, Core current operating frequency in MHz is
calculated as
follows:
[...]
@@ -658,19 +670,20 @@ void amd_log_freq(const struct cpuinfo_x86 *c)
if (!(lo >> 63))
return;
-#define FREQ(v) (c->x86 < 0x17 ? ((((v) & 0x3f) + 0x10) * 100) >>
(((v) >> 6) & 7) \
- : (((v) & 0xff) * 25 * 8) / (((v) >> 8) &
0x3f))
if (idx && idx < h &&
!rdmsr_safe(0xC0010064 + idx, val) && (val >> 63) &&
!rdmsr_safe(0xC0010064, hi) && (hi >> 63))
printk("CPU%u: %lu (%lu ... %lu) MHz\n",
- smp_processor_id(), FREQ(val), FREQ(lo), FREQ(hi));
+ smp_processor_id(),
+ amd_parse_freq(c, val),
+ amd_parse_freq(c, lo), amd_parse_freq(c, hi));
I fear Misra won't like multiple function calls to evaluate the
parameters
to pass to another function. Iirc smp_process_id() has special
exception,
so that's okay here. This may be possible to alleviate by marking the
new
helper pure or even const (see gcc doc as to caveats with passing
pointers
to const functions). Cc-ing Nicola for possible clarification or
correction.
Jan
Yes, it would help. Currently there is only a property for
smp_processor_id(), though there has been some discussion in the past
about adding a formal deviation. Not a big problem either way since
currently the rule is non-blocking, but definitely an attribute would
help any future work on making that clean.
--
Nicola Vetrini, B.Sc.
Software Engineer
BUGSENG (https://bugseng.com)
LinkedIn: https://www.linkedin.com/in/nicola-vetrini-a42471253
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