linux-kernel - Re: [PATCH v2 01/29] x86: treewide: Introduce x86_vendor_amd_or

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Message-ID: <Z9lUB2t0eZ8bz4vW@lx-t490>
Date: Tue, 18 Mar 2025 12:07:51 +0100
From: "Ahmed S. Darwish" <darwi@...utronix.de>
To: Borislav Petkov <bp@...en8.de>
Cc: Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	John Ogness <john.ogness@...utronix.de>, x86@...nel.org,
	x86-cpuid@...ts.linux.dev, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 01/29] x86: treewide: Introduce
 x86_vendor_amd_or_hygon()

Hi,

On Mon, 17 Mar 2025, Borislav Petkov wrote:
>
> On Mon, Mar 17, 2025, Ahmed S. Darwish wrote:
> > The pattern to check if an x86 vendor is AMD or HYGON (or not both) is
> > pretty common.  Introduce x86_vendor_amd_or_hygon() at <asm/processor.h>
>
> So if we need to check "intel too", we do
>
> x86_vendor_amd_or_hygon_or_intel?
>
> Nah, this is silly.
>

I needed this while refactoring the cacheinfo.c leaf 0x8000001d code at
patch 11/29 ("x86/cacheinfo: Consolidate AMD/Hygon leaf 0x8000001d
calls") as the combined check was done multiple times.

Then I found that there are 28 other cases in the x86 tree where the
AMD/Hygon CPU vendor check is also combined.  So I did that macro and it
also made a number the affected sites more succinct; e.g.:

|  diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
|  index 43dcd8c7badc..13df4917d7d8 100644
|  --- a/arch/x86/xen/enlighten.c
|  +++ b/arch/x86/xen/enlighten.c
|  @@ -82,11 +82,9 @@ void xen_hypercall_setfunc(void)
|   	if (static_call_query(xen_hypercall) != xen_hypercall_hvm)
|   		return;
|
|  -	if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
|  -	     boot_cpu_data.x86_vendor == X86_VENDOR_HYGON))
|  -		static_call_update(xen_hypercall, xen_hypercall_amd);
|  -	else
|  -		static_call_update(xen_hypercall, xen_hypercall_intel);
|  +	static_call_update(xen_hypercall,
|  +			   x86_vendor_amd_or_hygon(boot_cpu_data.x86_vendor) ?
|  +			   xen_hypercall_amd : xen_hypercall_intel);
|   }
|
|   /*
|  @@ -118,11 +116,8 @@ noinstr void *__xen_hypercall_setfunc(void)
|   	if (!boot_cpu_has(X86_FEATURE_CPUID))
|   		xen_get_vendor();
|
|  -	if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
|  -	     boot_cpu_data.x86_vendor == X86_VENDOR_HYGON))
|  -		func = xen_hypercall_amd;
|  -	else
|  -		func = xen_hypercall_intel;
|  +	func = x86_vendor_amd_or_hygon(boot_cpu_data.x86_vendor) ?
|  +		xen_hypercall_amd : xen_hypercall_intel;
|
|   	static_call_update_early(xen_hypercall, func);

Nonetheless, I've seen your other emails in the thread, and I'll drop the
patch.

Thanks!

--
Ahmed S. Darwish
Linutronix GmbH