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Re: [PATCH v2 01/16] x86/msr: Implement rdmsr_safe() in C
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 18 Aug 2025 13:23:36 +0200
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 18 Aug 2025 11:23:45 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 15.08.2025 22:41, Andrew Cooper wrote:
> ... in preparation to be able to use asm goto.
>
> Notably this mean that the value parameter must be taken by pointer rather
> than by value.
>
> No functional change.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
In principle
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
However, having looked at patch 2 first, ...
> @@ -879,14 +879,14 @@ static void intel_init_ppin(const struct cpuinfo_x86 *c)
> case 0x8f: /* Sapphire Rapids X */
>
> if ( (c != &boot_cpu_data && !ppin_msr) ||
> - rdmsr_safe(MSR_PPIN_CTL, val) )
> + rdmsr_safe(MSR_PPIN_CTL, &val) )
> return;
... with this, wouldn't we be better off using ...
> /* If PPIN is disabled, but not locked, try to enable. */
> if ( !(val & (PPIN_ENABLE | PPIN_LOCKOUT)) )
> {
> wrmsr_safe(MSR_PPIN_CTL, val | PPIN_ENABLE);
> - rdmsr_safe(MSR_PPIN_CTL, val);
> + rdmsr_safe(MSR_PPIN_CTL, &val);
... plain rdmsr() here, thus not leaving it open to the behavioral change
patch 2 comes with?
Jan
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