linux-kernel - Re: [PATCH] x86/coco, x86/sev: Use cpu_feature

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Message-ID: <20231205180813.phbxg5jdumfovshz@box.shutemov.name>
Date:   Tue, 5 Dec 2023 21:08:13 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Tom Lendacky <thomas.lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/coco, x86/sev: Use cpu_feature_enabled() to detect
 SEV guest flavor

On Tue, Dec 05, 2023 at 06:24:36PM +0100, Borislav Petkov wrote:
> On Tue, Dec 05, 2023 at 08:16:43PM +0300, Kirill A. Shutemov wrote:
> > What's wrong with using X86_FEATURE_* here?
> 
> What's wrong with using something which is already there?

It is here and it is broken.

I think legitimate use case for cc_platfrom_has() is to check platform
capability, not specific implementation. CC_ATTR_GUEST_MEM_ENCRYPT makes
sense, CC_ATTR_GUEST_SEV_SNP doesn't.

And we have much more mature infrastructure around X86_FEATURE_ comparing
to CC_ATRR_. If we can use it, we should.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov