[PATCH 04/11] x86/acpi: Check MWAIT feature instead of CPUID level

Dave Hansen
2024-11-20T19:53:33Z

From: Dave Hansen <dave.hansen@linux.intel.com>

I think this code is possibly buggy. The CPU could have a high
c->cpuid_level and not support MWAIT at all. It is much more clear to
just check for MWAIT support directly. Also, because of the CPU level
dependency code, any CPU that has X86_FEATURE_MWAIT also has a
high-enough CPUID level.

Check X86_FEATURE_MWAIT instead of the CPUID level.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
---

b/arch/x86/kernel/acpi/cstate.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff -puN arch/x86/kernel/acpi/cstate.c~mwait-leaf-checks-3 arch/x86/kernel/acpi/cstate.c
--- a/arch/x86/kernel/acpi/cstate.c~mwait-leaf-checks-3 2024-11-20 11:44:17.225650902 -0800
+++ b/arch/x86/kernel/acpi/cstate.c 2024-11-20 11:44:17.225650902 -0800
@@ -173,7 +173,7 @@ int acpi_processor_ffh_cstate_probe(unsi
struct cpuinfo_x86 *c = &cpu_data(cpu);
long retval;

- if (!cpu_cstate_entry || c->cpuid_level < CPUID_MWAIT_LEAF)
+ if (!cpu_cstate_entry || cpu_has(c, X86_FEATURE_MWAIT))
return -1;

if (reg->bit_offset != NATIVE_CSTATE_BEYOND_HALT)
_