linux-kernel - Re: [PATCH v6 3/5] x86/cpufeatures: Generate a feature mask header based on build config

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Message-ID: <8e4e1723-321a-4e8e-bbac-e2e5d8b08bfc@zytor.com>
Date: Tue, 4 Mar 2025 02:18:51 -0800
From: Xin Li <xin@...or.com>
To: Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>
Cc: "Aithal, Srikanth" <sraithal@....com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        dave.hansen@...ux.intel.com, x86@...nel.org, will@...nel.org,
        peterz@...radead.org, yury.norov@...il.com, akpm@...ux-foundation.org,
        acme@...nel.org, namhyung@...nel.org, brgerst@...il.com,
        andrew.cooper3@...rix.com, nik.borisov@...e.com
Subject: Re: [PATCH v6 3/5] x86/cpufeatures: Generate a feature mask header
 based on build config

On 3/3/2025 5:25 AM, Borislav Petkov wrote:
> On Mon, Mar 03, 2025 at 04:05:54AM -0800, H. Peter Anvin wrote:
>> "make headers" on an unconfigured tree should presumably only produce the uapi headers, not kernel-internal ones, one could surmise?
> 
> Well, that's kinda a question for you guys:
> 
> cfc7686900a87   (H. Peter Anvin (Intel) 2025-02-28 00:23:36 -0800       281)archheaders: $(out)/$(featuremasks_hdr)
> 1f57d5d85ba7f   (Ingo Molnar    2015-06-03 18:36:41 +0200       282)    $(Q)$(MAKE) $(build)=arch/x86/entry/syscalls all
> 
> and the headers target has
> 
> headers: $(version_h) scripts_unifdef uapi-asm-generic archheaders archscripts
> 
> as its prereq.
> 
> Judging by
> 
> 59b2bd05f5f4 ("kbuild: add 'headers' target to build up uapi headers in usr/include")

It seems that 'archprepare' works, however I'm not sure if it's the best
choice.  Any suggestion?

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 60583987d320..2db535958b8d 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -276,9 +276,9 @@ $(out)/$(featuremasks_hdr): $(featuremasks_awk) 
$(cpufeatures_hdr) $(KCONFIG_CON
	$(shell mkdir -p $(out))
	$(call if_changed,gen_featuremasks)

-targets += $(out)/$(featuremasks_hdr)
+archprepare: $(out)/$(featuremasks_hdr)

-archheaders: $(out)/$(featuremasks_hdr)
+archheaders:
	$(Q)$(MAKE) $(build)=arch/x86/entry/syscalls all

  ###

> 
> it sure looks like "make headers" should be for uapi headers only.
> 
> Oh, and it should be documented in "make help" output btw.

Want me to add it btw?

Thanks!
     Xin