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x86/cpu: Introduce and use CPUID leaf 0x2 parsing helpers

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Introduce CPUID leaf 0x2 parsing helpers at <asm/cpuid/leaf_0x2_api.h>.
This allows sharing the leaf 0x2's output validation and iteration logic
across both x86/cpu intel.c and cacheinfo.c.

Start by converting intel.c to the new API.

Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250324133324.23458-4-darwi@linutronix.de
This commit is contained in:
Ahmed S. Darwish
2025-03-24 14:32:58 +01:00
committed by Ingo Molnar
parent 09a1da4beb
commit fe78079ec0
4 changed files with 88 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
arch/x86/include/asm/cpuid.h
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@@ -4,5 +4,6 @@
#define _ASM_X86_CPUID_H
#include <asm/cpuid/api.h>
#include <asm/cpuid/leaf_0x2_api.h>
#endif /* _ASM_X86_CPUID_H */

65
arch/x86/include/asm/cpuid/leaf_0x2_api.h Normal file
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@@ -0,0 +1,65 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_CPUID_LEAF_0x2_API_H
#define _ASM_X86_CPUID_LEAF_0x2_API_H
#include <asm/cpuid/api.h>
#include <asm/cpuid/types.h>
/**
* cpuid_get_leaf_0x2_regs() - Return sanitized leaf 0x2 register output
* @regs: Output parameter
*
* Query CPUID leaf 0x2 and store its output in @regs. Force set any
* invalid 1-byte descriptor returned by the hardware to zero (the NULL
* cache/TLB descriptor) before returning it to the caller.
*
* Use for_each_leaf_0x2_desc() to iterate over the returned output.
*/
static inline void cpuid_get_leaf_0x2_regs(union leaf_0x2_regs *regs)
{
cpuid_leaf(0x2, regs);
/*
* All Intel CPUs must report an iteration count of 1. In case
* of bogus hardware, treat all returned descriptors as NULL.
*/
if (regs->desc[0] != 0x01) {
for (int i = 0; i < 4; i++)
regs->regv[i] = 0;
return;
}
/*
* The most significant bit (MSB) of each register must be clear.
* If a register is invalid, replace its descriptors with NULL.
*/
for (int i = 0; i < 4; i++) {
if (regs->reg[i].invalid)
regs->regv[i] = 0;
}
}
/**
* for_each_leaf_0x2_desc() - Iterator for CPUID leaf 0x2 descriptors
* @regs: Leaf 0x2 output, as returned by cpuid_get_leaf_0x2_regs()
* @desc: Pointer to the returned descriptor for each iteration
*
* Loop over the 1-byte descriptors in the passed leaf 0x2 output registers
* @regs. Provide each descriptor through @desc.
*
* Note that the first byte is skipped as it is not a descriptor.
*
* Sample usage::
*
* union leaf_0x2_regs regs;
* u8 *desc;
*
* cpuid_get_leaf_0x2_regs(&regs);
* for_each_leaf_0x2_desc(regs, desc) {
* // Handle *desc value
* }
*/
#define for_each_leaf_0x2_desc(regs, desc) \
for (desc = &(regs).desc[1]; desc < &(regs).desc[16]; desc++)
#endif /* _ASM_X86_CPUID_LEAF_0x2_API_H */

16
arch/x86/include/asm/cpuid/types.h
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@@ -29,4 +29,20 @@ enum cpuid_regs_idx {
#define CPUID_LEAF_FREQ 0x16
#define CPUID_LEAF_TILE 0x1d
/*
* Types for CPUID(0x2) parsing
* Check <asm/cpuid/leaf_0x2_api.h>
*/
struct leaf_0x2_reg {
u32 : 31,
invalid : 1;
};
union leaf_0x2_regs {
struct leaf_0x2_reg reg[4];
u32 regv[4];
u8 desc[16];
};
#endif /* _ASM_X86_CPUID_TYPES_H */

23
arch/x86/kernel/cpu/intel.c
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@@ -16,6 +16,7 @@
#include <asm/cpu_device_id.h>
#include <asm/cpufeature.h>
#include <asm/cpu.h>
#include <asm/cpuid.h>
#include <asm/hwcap2.h>
#include <asm/intel-family.h>
#include <asm/microcode.h>
@@ -778,27 +779,15 @@ static void intel_tlb_lookup(const unsigned char desc)
static void intel_detect_tlb(struct cpuinfo_x86 *c)
{
u32 regs[4];
u8 *desc = (u8 *)regs;
union leaf_0x2_regs regs;
u8 *desc;
if (c->cpuid_level < 2)
return;
cpuid(2, &regs[0], &regs[1], &regs[2], &regs[3]);
/* Intel CPUs must report an iteration count of 1 */
if (desc[0] != 0x01)
return;
/* If a register's bit 31 is set, it is an unknown format */
for (int i = 0; i < 4; i++) {
if (regs[i] & (1 << 31))
regs[i] = 0;
}
/* Skip the first byte as it is not a descriptor */
for (int i = 1; i < 16; i++)
intel_tlb_lookup(desc[i]);
cpuid_get_leaf_0x2_regs(&regs);
for_each_leaf_0x2_desc(regs, desc)
intel_tlb_lookup(*desc);
}
static const struct cpu_dev intel_cpu_dev = {