6.6-stable review patch. If anyone has any objections, please let me know.
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From: K Prateek Nayak kprateek.nayak@amd.com
[ Upstream commit e1bc02646527fc1ed74f00eb599b2b74d49671c7 ]
x86_sched_itmt_flags() returns SD_ASYM_PACKING if ITMT support is enabled by the system. Without ITMT support being enabled, it returns 0 similar to current x86_die_flags() on non-Hybrid systems (!X86_HYBRID_CPU and !X86_FEATURE_AMD_HETEROGENEOUS_CORES)
On Intel systems that enable ITMT support, either the MC domain coincides with the PKG domain, or in case of multiple MC groups within a PKG domain, either Sub-NUMA Cluster (SNC) is enabled or the processor features Hybrid core layout (X86_HYBRID_CPU) which leads to three distinct possibilities:
o If PKG and MC domains coincide, PKG domain is degenerated by sd_parent_degenerate() when building sched domain topology.
o If SNC is enabled, PKG domain is never added since "x86_has_numa_in_package" is set and the topology will instead contain NODE and NUMA domains.
o On X86_HYBRID_CPU which contains multiple MC groups within the PKG, the PKG domain requires x86_sched_itmt_flags().
Thus, on Intel systems that contains multiple MC groups within the PKG and enables ITMT support, the PKG domain requires x86_sched_itmt_flags(). In all other cases PKG domain is either never added or is degenerated. Thus, returning x86_sched_itmt_flags() unconditionally at PKG domain on Intel systems should not lead to any functional changes.
On AMD systems with multiple LLCs (MC groups) within a PKG domain, enabling ITMT support requires setting SD_ASYM_PACKING to the PKG domain since the core rankings are assigned PKG-wide.
Core rankings on AMD processors is currently set by the amd-pstate driver when Preferred Core feature is supported. A subset of systems that support Preferred Core feature can be detected using X86_FEATURE_AMD_HETEROGENEOUS_CORES however, this does not cover all the systems that support Preferred Core ranking.
Detecting Preferred Core support on AMD systems requires inspecting CPPC Highest Perf on all present CPUs and checking if it differs on at least one CPU. Previous suggestion to use a synthetic feature to detect Preferred Core support [1] was found to be non-trivial to implement since BSP alone cannot detect if Preferred Core is supported and by the time AP comes up, alternatives are patched and setting a X86_FEATURE_* then is not possible.
Since x86 processors enabling ITMT support that consists multiple non-NUMA MC groups within a PKG requires SD_ASYM_PACKING flag set at the PKG domain, return x86_sched_itmt_flags unconditionally for the PKG domain.
Since x86_die_flags() would have just returned x86_sched_itmt_flags() after the change, remove the unnecessary wrapper and pass x86_sched_itmt_flags() directly as the flags function.
Fixes: f3a052391822 ("cpufreq: amd-pstate: Enable amd-pstate preferred core support") Signed-off-by: K Prateek Nayak kprateek.nayak@amd.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Tim Chen tim.c.chen@linux.intel.com Link: https://lore.kernel.org/r/20241223043407.1611-6-kprateek.nayak@amd.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/smpboot.c | 11 +---------- 1 file changed, 1 insertion(+), 10 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 9150bd5147d01..a8f2ab816d5ae 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -604,15 +604,6 @@ static int x86_cluster_flags(void) } #endif
-static int x86_die_flags(void) -{ - if (cpu_feature_enabled(X86_FEATURE_HYBRID_CPU) || - cpu_feature_enabled(X86_FEATURE_AMD_HETEROGENEOUS_CORES)) - return x86_sched_itmt_flags(); - - return 0; -} - /* * Set if a package/die has multiple NUMA nodes inside. * AMD Magny-Cours, Intel Cluster-on-Die, and Intel @@ -648,7 +639,7 @@ static void __init build_sched_topology(void) */ if (!x86_has_numa_in_package) { x86_topology[i++] = (struct sched_domain_topology_level){ - cpu_cpu_mask, x86_die_flags, SD_INIT_NAME(PKG) + cpu_cpu_mask, x86_sched_itmt_flags, SD_INIT_NAME(PKG) }; }