x86/cpu: Expose only stepping min/max interface

The x86_match_cpu() infrastructure can match CPU steppings. Since
there are only 16 possible steppings, the matching infrastructure goes
all out and stores the stepping match as a bitmap. That means it can
match any possible steppings in a single list entry. Fun.

But it exposes this bitmap to each of the X86_MATCH_*() helpers when
none of them really need a bitmap. It makes up for this by exporting a
helper (X86_STEPPINGS()) which converts a contiguous stepping range
into the bitmap which every single user leverages.

Instead of a bitmap, have the main helper for this sort of thing
(X86_MATCH_VFM_STEPS()) just take a stepping range. This ends up
actually being even more compact than before.

Leave the helper in place (renamed to __X86_STEPPINGS()) to make it
more clear what is going on instead of just having a random GENMASK()
in the middle of an already complicated macro.

One oddity that I hit was this macro:

       X86_MATCH_VFM_STEPS(vfm, X86_STEPPING_MIN, max_stepping, issues)

It *could* have been converted over to take a min/max stepping value
for each entry. But that would have been a bit too verbose and would
prevent the one oddball in the list (INTEL_COMETLAKE_L stepping 0)
from sticking out.

Instead, just have it take a *maximum* stepping and imply that the match
is from 0=>max_stepping. This is functional for all the cases now and
also retains the nice property of having INTEL_COMETLAKE_L stepping 0
stick out like a sore thumb.

skx_cpuids[] is goofy. It uses the stepping match but encodes all
possible steppings. Just use a normal, non-stepping match helper.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20241213185129.65527B2A%40davehans-spike.ostc.intel.com

1 files changed, 9 insertions, 9 deletions

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index c5fb28e6451a..b16bda1ffaab 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -509,19 +509,19 @@ static struct clock_event_device lapic_clockevent = {
 static DEFINE_PER_CPU(struct clock_event_device, lapic_events);
 
 static const struct x86_cpu_id deadline_match[] __initconst = {
-	X86_MATCH_VFM_STEPPINGS(INTEL_HASWELL_X, X86_STEPPINGS(0x2, 0x2), 0x3a), /* EP */
-	X86_MATCH_VFM_STEPPINGS(INTEL_HASWELL_X, X86_STEPPINGS(0x4, 0x4), 0x0f), /* EX */
+	X86_MATCH_VFM_STEPS(INTEL_HASWELL_X,   0x2, 0x2, 0x3a), /* EP */
+	X86_MATCH_VFM_STEPS(INTEL_HASWELL_X,   0x4, 0x4, 0x0f), /* EX */
 
 	X86_MATCH_VFM(INTEL_BROADWELL_X,	0x0b000020),
 
-	X86_MATCH_VFM_STEPPINGS(INTEL_BROADWELL_D, X86_STEPPINGS(0x2, 0x2), 0x00000011),
-	X86_MATCH_VFM_STEPPINGS(INTEL_BROADWELL_D, X86_STEPPINGS(0x3, 0x3), 0x0700000e),
-	X86_MATCH_VFM_STEPPINGS(INTEL_BROADWELL_D, X86_STEPPINGS(0x4, 0x4), 0x0f00000c),
-	X86_MATCH_VFM_STEPPINGS(INTEL_BROADWELL_D, X86_STEPPINGS(0x5, 0x5), 0x0e000003),
+	X86_MATCH_VFM_STEPS(INTEL_BROADWELL_D, 0x2, 0x2, 0x00000011),
+	X86_MATCH_VFM_STEPS(INTEL_BROADWELL_D, 0x3, 0x3, 0x0700000e),
+	X86_MATCH_VFM_STEPS(INTEL_BROADWELL_D, 0x4, 0x4, 0x0f00000c),
+	X86_MATCH_VFM_STEPS(INTEL_BROADWELL_D, 0x5, 0x5, 0x0e000003),
 
-	X86_MATCH_VFM_STEPPINGS(INTEL_SKYLAKE_X, X86_STEPPINGS(0x3, 0x3), 0x01000136),
-	X86_MATCH_VFM_STEPPINGS(INTEL_SKYLAKE_X, X86_STEPPINGS(0x4, 0x4), 0x02000014),
-	X86_MATCH_VFM_STEPPINGS(INTEL_SKYLAKE_X, X86_STEPPINGS(0x5, 0xf), 0),
+	X86_MATCH_VFM_STEPS(INTEL_SKYLAKE_X,   0x3, 0x3, 0x01000136),
+	X86_MATCH_VFM_STEPS(INTEL_SKYLAKE_X,   0x4, 0x4, 0x02000014),
+	X86_MATCH_VFM_STEPS(INTEL_SKYLAKE_X,   0x5, 0xf, 0),
 
 	X86_MATCH_VFM(INTEL_HASWELL,		0x22),
 	X86_MATCH_VFM(INTEL_HASWELL_L,		0x20),