Re: [PATCH 1/5] x86/cpu: Introduce new microcode matching helper

[Chao Gao]

On Fri, Dec 06, 2024 at 11:38:31AM -0800, Dave Hansen wrote:
>
>From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
>
>The 'x86_cpu_id' and 'x86_cpu_desc' structures are very similar and
>need to be consolidated.  There is a microcode version matching
>function for 'x86_cpu_desc' but not 'x86_cpu_id'.
>
>Create one for 'x86_cpu_id'.
>
>This essentially just leverages the x86_cpu_id->driver_data field
>to replace the less generic x86_cpu_desc->x86_microcode_rev field.
>
>Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
>---
>
> b/arch/x86/include/asm/cpu_device_id.h |    1 +
> b/arch/x86/kernel/cpu/match.c          |   11 +++++++++++
> 2 files changed, 12 insertions(+)
>
>diff -puN arch/x86/include/asm/cpu_device_id.h~min-ucode-rev arch/x86/include/asm/cpu_device_id.h
>--- a/arch/x86/include/asm/cpu_device_id.h~min-ucode-rev	2024-12-06 11:33:15.663128241 -0800
>+++ b/arch/x86/include/asm/cpu_device_id.h	2024-12-06 11:33:15.667128399 -0800
>@@ -278,5 +278,6 @@ struct x86_cpu_desc {
> 
> extern const struct x86_cpu_id *x86_match_cpu(const struct x86_cpu_id *match);
> extern bool x86_cpu_has_min_microcode_rev(const struct x86_cpu_desc *table);
>+extern bool x86_match_min_microcode_rev(const struct x86_cpu_id *table);
> 
> #endif /* _ASM_X86_CPU_DEVICE_ID */
>diff -puN arch/x86/kernel/cpu/match.c~min-ucode-rev arch/x86/kernel/cpu/match.c
>--- a/arch/x86/kernel/cpu/match.c~min-ucode-rev	2024-12-06 11:33:15.663128241 -0800
>+++ b/arch/x86/kernel/cpu/match.c	2024-12-06 11:33:15.667128399 -0800
>@@ -86,3 +86,14 @@ bool x86_cpu_has_min_microcode_rev(const
> 	return true;
> }
> EXPORT_SYMBOL_GPL(x86_cpu_has_min_microcode_rev);
>+
>+bool x86_match_min_microcode_rev(const struct x86_cpu_id *table)
>+{
>+	const struct x86_cpu_id *res = x86_match_cpu(table);
>+
>+	if (!res || res->driver_data > boot_cpu_data.microcode)
>+		return false;
>+
>+	return true;

Maybe we can simplify the logic to:

	return res && res->driver_data <= boot_cpu_data.microcode;

>+}
>+EXPORT_SYMBOL_GPL(x86_match_min_microcode_rev);
>_