Re: [PATCH v1 10/40] x86/cpu: Remove leaf 0x2 parsing loop and add helpers

Ingo Molnar
2025-03-04T09:26:08Z

* Ahmed S. Darwish <darwi@linutronix.de> wrote:

> Leaf 0x2 output includes a "query count" byte where it was supposed to
> specify the number of repeated cpuid leaf 0x2 subleaf 0 queries needed
> to extract all of the hardware's cache and TLB descriptors.

s/cpuid
/CPUID

Please do this in the rest of the series too. (I did it for the first 9
patches.)

> +++ b/arch/x86/include/asm/cpuid/types.h
> @@ -0,0 +1,79 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_X86_CPUID_TYPES_H
> +#define _ASM_X86_CPUID_TYPES_H
> +
> +#include <linux/types.h>
> +
> +#include <asm/cpuid.h>

So that header organization is a bit messy: if <asm/cpuid.h> is
supposed to be the main header, why is there a <asm/cpuid/types.h>?

I'd suggest we follow the FPU header structure:

starship:~/tip/arch/x86/include/asm/fpu> ls -l
total 48
-rw-rw-r-- 1 mingo mingo 5732 Feb 27 19:24 api.h
-rw-rw-r-- 1 mingo mingo 671 Feb 26 16:13 regset.h
-rw-rw-r-- 1 mingo mingo 2203 Feb 27 13:52 sched.h
-rw-rw-r-- 1 mingo mingo 1110 Feb 27 19:24 signal.h
-rw-rw-r-- 1 mingo mingo 14741 Feb 27 19:24 types.h
-rw-rw-r-- 1 mingo mingo 811 Feb 26 16:13 xcr.h
-rw-rw-r-- 1 mingo mingo 4401 Feb 27 23:01 xstate.h

With <asm/cpuid/api.h> being the main header - established via a
separate preparatory patch.

This followup patch can then add <asm/cpuid/types.h> which will also be
included in <asm/cpuid/api.h>.

> +/*
> + * CPUID(0x2) parsing helpers
> + * Check for_each_leaf_0x2_desc() documentation.
> + */
> +
> +struct leaf_0x2_reg {
> + u32 : 31,
> + invalid : 1;
> +};
> +
> +union leaf_0x2_regs {
> + struct leaf_0x2_reg reg[4];
> + u32 regv[4];
> + u8 desc[16];
> +};
> +
> +/**
> + * get_leaf_0x2_regs() - Return sanitized leaf 0x2 register output
> + * @regs: Output parameter
> + *
> + * Get leaf 0x2 register output and store it in @regs. Invalid byte
> + * descriptors returned by the hardware will be force set to zero (the
> + * NULL cache/TLB descriptor) before returning them to the caller.
> + */
> +static inline void get_leaf_0x2_regs(union leaf_0x2_regs *regs)

Please prefix all new cpuid API functions and types with cpuid_.

> +#define for_each_leaf_0x2_desc(regs, desc) \
> + /* Skip the first byte as it is not a descriptor */ \
> + for (desc = &(regs).desc[1]; desc < &(regs).desc[16]; desc++)

The comment line can come before the macro.

> + get_leaf_0x2_regs(&regs);
> + for_each_leaf_0x2_desc(regs, desc)
> + intel_tlb_lookup(*desc);

Nice interface otherwise.

Thanks,

Ingo