Re: [PATCH 09/15] x86, amd: add accessor for number of cores per compute unit

Guenter Roeck
2015-08-27T17:27:55Z

On Thu, Aug 27, 2015 at 04:07:40PM +0800, Huang Rui wrote:
> Add an accessor function amd_get_cores_per_cu() which returns the
> number of cores per compute unit.
>
> In a subsequent patch, we will use this function in fam15h_power
> driver.
>
> Signed-off-by: Huang Rui <ray.huang@amd.com>
> ---
> arch/x86/include/asm/processor.h | 1 +
> arch/x86/kernel/cpu/amd.c | 19 +++++++++++++++++--
> 2 files changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 19577dd..831ad682 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -810,6 +810,7 @@ static inline int mpx_disable_management(void)
>
> extern u16 amd_get_nb_id(int cpu);
> extern u32 amd_get_nodes_per_socket(void);
> +extern u32 amd_get_cores_per_cu(void);
>
> static inline uint32_t hypervisor_cpuid_base(const char *sig, uint32_t leaves)
> {
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index 51ad2af..8ab939a 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -26,6 +26,9 @@
> */
> static u32 nodes_per_socket = 1;
>
> +/* cores_per_cu: stores the number of cores per compute unit */
> +static u32 cores_per_cu = 1;
> +
Is this value going to be constant even if there are multiple CPUs
in the system ? In other words, if there are multiple CPUs, do
they always have to have the same number of cores per CU ?

Thanks,
Guenter

> static inline int rdmsrl_amd_safe(unsigned msr, unsigned long long *p)
> {
> u32 gprs[8] = { 0 };
> @@ -298,7 +301,6 @@ static int nearby_node(int apicid)
> #ifdef CONFIG_SMP
> static void amd_get_topology(struct cpuinfo_x86 *c)
> {
> - u32 cores_per_cu = 1;
> u8 node_id;
> int cpu = smp_processor_id();
>
> @@ -313,7 +315,6 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
> /* get compute unit information */
> smp_num_siblings = ((ebx >> 8) & 3) + 1;
> c->compute_unit_id = ebx & 0xff;
> - cores_per_cu += ((ebx >> 8) & 3);
> } else if (cpu_has(c, X86_FEATURE_NODEID_MSR)) {
> u64 value;
>
> @@ -379,6 +380,13 @@ u32 amd_get_nodes_per_socket(void)
> }
> EXPORT_SYMBOL_GPL(amd_get_nodes_per_socket);
>
> +/* this function returns the number of cores per compute unit */
> +u32 amd_get_cores_per_cu(void)
> +{
> + return cores_per_cu;
> +}
> +EXPORT_SYMBOL_GPL(amd_get_cores_per_cu);
> +
> static void srat_detect_node(struct cpuinfo_x86 *c)
> {
> #ifdef CONFIG_NUMA
> @@ -506,6 +514,13 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
> /* A random value per boot for bit slice [12:upper_bit) */
> va_align.bits = get_random_int() & va_align.mask;
> }
> +
> + if (cpu_has_topoext) {
> + u32 cpuid;
> +
> + cpuid = cpuid_ebx(0x8000001e);
> + cores_per_cu += ((cpuid >> 8) & 3);
> + }
> }
>
> static void early_init_amd(struct cpuinfo_x86 *c)
> --
> 1.9.1
>