Re: [PATCH v13 02/14] x86/mm: get INVLPGB count max from CPUID

Borislav Petkov
2025-02-24T12:01:03Z

On Sun, Feb 23, 2025 at 02:48:52PM -0500, Rik van Riel wrote:
> diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
> index 3da645139748..09463a2fb05f 100644
> --- a/arch/x86/include/asm/tlbflush.h
> +++ b/arch/x86/include/asm/tlbflush.h
> @@ -183,6 +183,9 @@ static inline void cr4_init_shadow(void)
> extern unsigned long mmu_cr4_features;
> extern u32 *trampoline_cr4_features;
>
> +/* How many pages can we invalidate with one INVLPGB. */

"... can be invalidated... "

Please use passive voice in your text: no "we" or "I", etc,
and describe your changes in imperative mood.

Bottom line is: personal pronouns are ambiguous in text, especially with
so many parties/companies/etc developing the kernel so let's avoid them
please.

Please check all your text.

> +extern u16 invlpgb_count_max;
> +
> extern void initialize_tlbstate_and_flush(void);
>
> /*
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index 54194f5995de..3e8180354303 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -29,6 +29,8 @@
>
> #include "cpu.h"
>
> +u16 invlpgb_count_max __ro_after_init;
> +
> static inline int rdmsrl_amd_safe(unsigned msr, unsigned long long *p)
> {
> u32 gprs[8] = { 0 };
> @@ -1139,6 +1141,12 @@ static void cpu_detect_tlb_amd(struct cpuinfo_x86 *c)
> tlb_lli_2m[ENTRIES] = eax & mask;
>
> tlb_lli_4m[ENTRIES] = tlb_lli_2m[ENTRIES] >> 1;
> +
> + /* Max number of pages INVLPGB can invalidate in one shot */
> + if (boot_cpu_has(X86_FEATURE_INVLPGB)) {
> + cpuid(0x80000008, &eax, &ebx, &ecx, &edx);
> + invlpgb_count_max = (edx & 0xffff) + 1;
> + }
> }

Ontop:

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 3e8180354303..7a72ef47a983 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -1143,10 +1143,8 @@ static void cpu_detect_tlb_amd(struct cpuinfo_x86 *c)
tlb_lli_4m[ENTRIES] = tlb_lli_2m[ENTRIES] >> 1;

/* Max number of pages INVLPGB can invalidate in one shot */
- if (boot_cpu_has(X86_FEATURE_INVLPGB)) {
- cpuid(0x80000008, &eax, &ebx, &ecx, &edx);
- invlpgb_count_max = (edx & 0xffff) + 1;
- }
+ if (cpu_has(c, X86_FEATURE_INVLPGB))
+ invlpgb_count_max = (cpuid_edx(0x80000008) & 0xffff) + 1;
}

static const struct cpu_dev amd_cpu_dev = {

--
Regards/Gruss,
Boris.