Re: [PATCH] x86: Report Intel platform_id in /proc/cpuinfo

Andi Kleen
2016-06-21T16:07:44Z

Andi Kleen <andi@firstfloor.org> writes:

Ping! Any comments on this patch?

> From: Andi Kleen <ak@linux.intel.com>
>
> We have a need to distinguish systems based on their platform ID.
> For example this is useful to distinguish systems with L4 cache
> versus ones without.
>
> There is a 3 bit identifier (also called processor flags) in
> the IA32_PLATFORM_ID MSR that can give a more fine grained
> identification of the CPU than just the model number/stepping.
>
> IA32_PLATFORM_ID is architectural.
>
> The processor flags are already used in the microcode driver.
> The MSR can be also accessed through /dev/cpu/*/msr, but that
> requires root and is awkward.
>
> This patch just exports the value retrieved by the microcode
> driver in /proc/cpuinfo. If the microcode driver is disabled
> it won't be shown, but that seems reasonable.
>
> v2: Handle 0 platform_id. Fix commit message.
> Cc: hmh@hmh.eng.br
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> ---
> arch/x86/include/asm/processor.h | 2 ++
> arch/x86/kernel/cpu/microcode/intel.c | 2 ++
> arch/x86/kernel/cpu/proc.c | 2 ++
> 3 files changed, 6 insertions(+)
>
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 20c11d1..270209c 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -136,6 +136,8 @@ struct cpuinfo_x86 {
> /* Index into per_cpu list: */
> u16 cpu_index;
> u32 microcode;
> + u32 platform_id;
> + u8 has_platform_id;
> };
>
> #define X86_VENDOR_INTEL 0
> diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
> index ee81c54..bcd3f59 100644
> --- a/arch/x86/kernel/cpu/microcode/intel.c
> +++ b/arch/x86/kernel/cpu/microcode/intel.c
> @@ -812,6 +812,8 @@ static int collect_cpu_info(int cpu_num, struct cpu_signature *csig)
> /* get processor flags from MSR 0x17 */
> rdmsr(MSR_IA32_PLATFORM_ID, val[0], val[1]);
> csig->pf = 1 << ((val[1] >> 18) & 7);
> + cpu_data(cpu_num).platform_id = (val[1] >> 18) & 7;
> + cpu_data(cpu_num).has_platform_id = true;
> }
>
> csig->rev = c->microcode;
> diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
> index 18ca99f..5345d50 100644
> --- a/arch/x86/kernel/cpu/proc.c
> +++ b/arch/x86/kernel/cpu/proc.c
> @@ -76,6 +76,8 @@ static int show_cpuinfo(struct seq_file *m, void *v)
> seq_puts(m, "stepping\t: unknown\n");
> if (c->microcode)
> seq_printf(m, "microcode\t: 0x%x\n", c->microcode);
> + if (c->has_platform_id)
> + seq_printf(m, "platform_id\t: %d\n", c->platform_id);
>
> if (cpu_has(c, X86_FEATURE_TSC)) {
> unsigned int freq = cpufreq_quick_get(cpu);

--
ak@linux.intel.com -- Speaking for myself only