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Re: [PATCH] x86/vpmu: Simplify is_pmc_quirk
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 21 Jun 2023 10:16:59 +0200
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Wed, 21 Jun 2023 08:17:51 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 20.06.2023 19:45, Andrew Cooper wrote:
> This should be static, and there's no need for a separate (non-init, even)
> function to perform a simple equality test. Drop the is_ prefix which is
> gramatically questionable, and make it __ro_after_init.
>
> Leave a TODO, because the behaviour is definitely wrong to be applied to ~all
> modern Intel CPUs, and has been raised on xen-devel previously without
> conclusion.
>
> No functional change.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
with one request:
> @@ -967,7 +960,8 @@ const struct arch_vpmu_ops *__init core2_vpmu_init(void)
> sizeof(uint64_t) * fixed_pmc_cnt +
> sizeof(struct xen_pmu_cntr_pair) * arch_pmc_cnt;
>
> - check_pmc_quirk();
> + /* TODO: This is surely wrong. */
> + pmc_quirk = current_cpu_data.x86 == 6;
In the description you say "~all modern Intel CPUs", which suggests it might
be correct for old enough ones. Would you mind weakening the comment to
"This surely isn't universally correct" or some such?
Jan
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