Re: [PATCH v15 09/13] tsc: Use the GUEST_TSC_FREQ MSR for discovering TSC frequency

Borislav Petkov
2024-12-30T11:29:22Z

On Tue, Dec 03, 2024 at 02:30:41PM +0530, Nikunj A Dadhania wrote:
> Subject: Re: [PATCH v15 09/13] tsc: Use the GUEST_TSC_FREQ MSR for...

The tip tree preferred format for patch subject prefixes is
'subsys/component:', e.g. 'x86/apic:', 'x86/mm/fault:', 'sched/fair:',
'genirq/core:'. Please do not use file names or complete file paths as
prefix. 'git log path/to/file' should give you a reasonable hint in most
cases.

Audit your whole set pls.

> +void __init snp_secure_tsc_init(void)
> +{
> + x86_platform.calibrate_cpu = securetsc_get_tsc_khz;
> + x86_platform.calibrate_tsc = securetsc_get_tsc_khz;

The fact that you assign the same function to two different function ptrs
already hints at some sort of improper functionality split.

> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
> index 67aeaba4ba9c..c0eef924b84e 100644
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -30,6 +30,7 @@
> #include <asm/i8259.h>
> #include <asm/topology.h>
> #include <asm/uv/uv.h>
> +#include <asm/sev.h>
>
> unsigned int __read_mostly cpu_khz; /* TSC clocks / usec, not used here */
> EXPORT_SYMBOL(cpu_khz);
> @@ -1515,6 +1516,10 @@ void __init tsc_early_init(void)
> /* Don't change UV TSC multi-chassis synchronization */
> if (is_early_uv_system())
> return;
> +
> + if (cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC))
> + snp_secure_tsc_init();

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index aac066d798ef..24e7c6cf3e29 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -3287,6 +3287,9 @@ static unsigned long securetsc_get_tsc_khz(void)

void __init snp_secure_tsc_init(void)
{
+ if (!cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC))
+ return;
+
x86_platform.calibrate_cpu = securetsc_get_tsc_khz;
x86_platform.calibrate_tsc = securetsc_get_tsc_khz;
}
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index c0eef924b84e..0864b314c26a 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1517,8 +1517,7 @@ void __init tsc_early_init(void)
if (is_early_uv_system())
return;

- if (cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC))
- snp_secure_tsc_init();
+ snp_secure_tsc_init();

if (!determine_cpu_tsc_frequencies(true))
return;

--
Regards/Gruss,
Boris.