With X86_FEATURE_TOPOEXT, current logic default to using APIC ID
to calculate cpumask for shared_cpu_map. However, since APIC IDs
are not guarantee to be contiguous for cores across different L3,
such as in family17h system w/ downcore configuration.
This results in incorrect L3 shared_cpu_map.
Instead, it should be safe to always use the pre-calculated
cpu_llc_shared_mask to derive L3 shared_cpu_map.
Signed-off-by: Suravee Suthikulpanit <[email protected]>
---
arch/x86/kernel/cpu/intel_cacheinfo.c | 28 ++++++++++++++--------------
1 file changed, 14 insertions(+), 14 deletions(-)
diff --git a/arch/x86/kernel/cpu/intel_cacheinfo.c b/arch/x86/kernel/cpu/intel_cacheinfo.c
index c55fb2c..10427bb 100644
--- a/arch/x86/kernel/cpu/intel_cacheinfo.c
+++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
@@ -811,7 +811,20 @@ static int __cache_amd_cpumap_setup(unsigned int cpu, int index,
struct cacheinfo *this_leaf;
int i, sibling;
- if (boot_cpu_has(X86_FEATURE_TOPOEXT)) {
+ if (index == 3) {
+ for_each_cpu(i, cpu_llc_shared_mask(cpu)) {
+ this_cpu_ci = get_cpu_cacheinfo(i);
+ if (!this_cpu_ci->info_list)
+ continue;
+ this_leaf = this_cpu_ci->info_list + index;
+ for_each_cpu(sibling, cpu_llc_shared_mask(cpu)) {
+ if (!cpu_online(sibling))
+ continue;
+ cpumask_set_cpu(sibling,
+ &this_leaf->shared_cpu_map);
+ }
+ }
+ } else if (boot_cpu_has(X86_FEATURE_TOPOEXT)) {
unsigned int apicid, nshared, first, last;
this_leaf = this_cpu_ci->info_list + index;
@@ -839,19 +852,6 @@ static int __cache_amd_cpumap_setup(unsigned int cpu, int index,
&this_leaf->shared_cpu_map);
}
}
- } else if (index == 3) {
- for_each_cpu(i, cpu_llc_shared_mask(cpu)) {
- this_cpu_ci = get_cpu_cacheinfo(i);
- if (!this_cpu_ci->info_list)
- continue;
- this_leaf = this_cpu_ci->info_list + index;
- for_each_cpu(sibling, cpu_llc_shared_mask(cpu)) {
- if (!cpu_online(sibling))
- continue;
- cpumask_set_cpu(sibling,
- &this_leaf->shared_cpu_map);
- }
- }
} else
return 0;
--
2.7.4
On Thu, Jul 20, 2017 at 04:52:08AM -0500, Suravee Suthikulpanit wrote:
> With X86_FEATURE_TOPOEXT, current logic default to using APIC ID
> to calculate cpumask for shared_cpu_map. However, since APIC IDs
> are not guarantee to be contiguous for cores across different L3,
> such as in family17h system w/ downcore configuration.
> This results in incorrect L3 shared_cpu_map.
There are syntactic and formulation errors in this paragraph, it reads
funny. Please improve.
> Instead, it should be safe to always use the pre-calculated
> cpu_llc_shared_mask to derive L3 shared_cpu_map.
"should"?!?
What does that mean? You tested it on relevant machines or you're hoping
that nothing would go wrong?
> Signed-off-by: Suravee Suthikulpanit <[email protected]>
> ---
> arch/x86/kernel/cpu/intel_cacheinfo.c | 28 ++++++++++++++--------------
> 1 file changed, 14 insertions(+), 14 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/intel_cacheinfo.c b/arch/x86/kernel/cpu/intel_cacheinfo.c
> index c55fb2c..10427bb 100644
> --- a/arch/x86/kernel/cpu/intel_cacheinfo.c
> +++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
> @@ -811,7 +811,20 @@ static int __cache_amd_cpumap_setup(unsigned int cpu, int index,
> struct cacheinfo *this_leaf;
> int i, sibling;
>
> - if (boot_cpu_has(X86_FEATURE_TOPOEXT)) {
> + if (index == 3) {
> + for_each_cpu(i, cpu_llc_shared_mask(cpu)) {
> + this_cpu_ci = get_cpu_cacheinfo(i);
> + if (!this_cpu_ci->info_list)
> + continue;
> + this_leaf = this_cpu_ci->info_list + index;
> + for_each_cpu(sibling, cpu_llc_shared_mask(cpu)) {
> + if (!cpu_online(sibling))
> + continue;
> + cpumask_set_cpu(sibling,
> + &this_leaf->shared_cpu_map);
> + }
> + }
> + } else if (boot_cpu_has(X86_FEATURE_TOPOEXT)) {
So this leaves more questions open than before it:
* Is cpu_llc_shared_map now *the* mask for the L3?
* Is the X86_FEATURE_TOPOEXT thing still going to be used for the other cache
levels? Apparently yes, I guess.
IOW, what is the big picture here? I could use some more details in the
commit message about it.
--
Regards/Gruss,
Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--