From: Sean Christopherson <seanjc@google.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@intel.com>, X86 ML <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86/cpu: Start documenting what the X86_FEATURE_ flag testing macros do
Date: Thu, 10 Nov 2022 23:27:08 +0000 [thread overview]
Message-ID: <Y22IzA9DN/xYWgWN@google.com> (raw)
In-Reply-To: <Y2okdzF60XHLCK2v@zn.tnic>
On Tue, Nov 08, 2022, Borislav Petkov wrote:
> On Mon, Nov 07, 2022 at 02:13:52PM -0800, Dave Hansen wrote:
> > It seems to be mildly warning against using _static_cpu_has()
> > indiscriminately. Should we tone that down a bit if we're recommending
> > implicit use of static_cpu_has() via cpu_feature_enabled() everywhere?
>
> Yeah, that comment is mine AFAIR. I was thinking of simply removing
> it as part of a long-term effort of converting everything to
> cpu_feature_enabled() and hiding static_cpu_has() eventually...
What about doing the opposite and folding cpu_feature_enabled()'s build-time
functionality into static_cpu_has() _and_ boot_cpu_has(), and then dropping
cpu_feature_enabled()? That way the tradeoffs of using the static variant are
still captured in code (cpu_feature_enabled() sounds too innocuous to my ears),
and as an added bonus even slow paths benefit from build-time disabling of features.
Hiding the use of alternatives in cpu_feature_enabled() seems like it will lead to
unnecessary code patching.
next prev parent reply other threads:[~2022-11-10 23:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-07 21:15 [PATCH] x86/cpu: Start documenting what the X86_FEATURE_ flag testing macros do Borislav Petkov
2022-11-07 22:13 ` Dave Hansen
2022-11-08 9:42 ` Borislav Petkov
2022-11-10 23:27 ` Sean Christopherson [this message]
2023-01-19 9:47 ` Borislav Petkov
2023-01-20 0:35 ` Sean Christopherson
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