Messages in this thread Patch in this message | | | From | David Woodhouse <> | Subject | [PATCH] x86/cpuid: Fewer CPUID invocations in init_scattered_cpuid_features() | Date | Tue, 23 Jan 2018 14:53:33 +0000 |
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We were doing a fresh CPUID for every single bit in every single output register. Do it once and then harvest *all* the bits we want.
We were also doing the max_level check with a new CPUID invocation for every single bit. Stop that too.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> --- Spotted this in my travels; it offended me.
arch/x86/kernel/cpu/scattered.c | 27 +++++++++++++++++++++------ 1 file changed, 21 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c index df11f5d..26c15fb 100644 --- a/arch/x86/kernel/cpu/scattered.c +++ b/arch/x86/kernel/cpu/scattered.c @@ -23,8 +23,8 @@ static const struct cpuid_bit cpuid_bits[] = { { X86_FEATURE_EPB, CPUID_ECX, 3, 0x00000006, 0 }, { X86_FEATURE_CAT_L3, CPUID_EBX, 1, 0x00000010, 0 }, { X86_FEATURE_CAT_L2, CPUID_EBX, 2, 0x00000010, 0 }, - { X86_FEATURE_CDP_L3, CPUID_ECX, 2, 0x00000010, 1 }, { X86_FEATURE_MBA, CPUID_EBX, 3, 0x00000010, 0 }, + { X86_FEATURE_CDP_L3, CPUID_ECX, 2, 0x00000010, 1 }, { X86_FEATURE_HW_PSTATE, CPUID_EDX, 7, 0x80000007, 0 }, { X86_FEATURE_CPB, CPUID_EDX, 9, 0x80000007, 0 }, { X86_FEATURE_PROC_FEEDBACK, CPUID_EDX, 11, 0x80000007, 0 }, @@ -38,20 +38,35 @@ void init_scattered_cpuid_features(struct cpuinfo_x86 *c) u32 regs[4]; const struct cpuid_bit *cb; + /* Max level for basic CPUID leaves */ + max_level = cpuid_eax(0); + for (cb = cpuid_bits; cb->feature; cb++) { + /* Are we on to extended CPUID leaves yet? */ + if (cb->level >= 0x80000000 && max_level < 0x80000000) { + max_level = cpuid_eax(0x80000000); + if (max_level < 0x80000000 || max_level > 0x8000ffff) { + /* No extended leaves are supported */ + break; + } + } + /* Verify that the level is valid */ - max_level = cpuid_eax(cb->level & 0xffff0000); - if (max_level < cb->level || - max_level > (cb->level | 0xffff)) + if (cb->level > max_level) continue; cpuid_count(cb->level, cb->sub_leaf, ®s[CPUID_EAX], ®s[CPUID_EBX], ®s[CPUID_ECX], ®s[CPUID_EDX]); - if (regs[cb->reg] & (1 << cb->bit)) - set_cpu_cap(c, cb->feature); + do { + if (regs[cb->reg] & (1 << cb->bit)) + set_cpu_cap(c, cb->feature); + + } while (cb[1].level == cb[0].level && + cb[1].sub_leaf == cb[0].sub_leaf && + cb++); } } -- 2.7.4
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