linux-kernel - Re: [PATCH RFC v9 05/51] x86/coco: move CONFIG_HAS_CC

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Message-ID: <20230629210204.tknoh7p3hw45jcp4@amd.com>
Date:   Thu, 29 Jun 2023 16:02:04 -0500
From:   Michael Roth <michael.roth@....com>
To:     Borislav Petkov <bp@...en8.de>
CC:     <kvm@...r.kernel.org>, <linux-coco@...ts.linux.dev>,
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        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH RFC v9 05/51] x86/coco: move CONFIG_HAS_CC_PLATFORM check
 down into coco/Makefile

On Wed, Jun 21, 2023 at 10:54:00AM +0200, Borislav Petkov wrote:
> On Tue, Jun 20, 2023 at 03:43:15PM -0500, Michael Roth wrote:
> > Basically, arch/x86/coco/Makefile is never processed if arch/x86/Kbuild
> > indicates that CONFIG_HAS_CC_PLATFORM is not set. So if we want to have
> > stuff in arch/x86/coco/Makefile that build for !CONFIG_HAS_CC_PLATFORM,
> > like SNP host support, which does not rely on CONFIG_HAS_CC_PLATFORM
> > being set, that check needs to be moved down into arch/x86/coco/Makefile.
> 
> Ok, so if you put SNP host support into arch/x86/virt/svm/sev.c, that
> should work too and won't have any relation to CONFIG_HAS_CC_PLATFORM,
> right?

Right, that works out just as well, and ends up being a bit more
straightforward. I have it implemented here:

  https://github.com/mdroth/linux/commits/snp-host-latest-v9b

  https://github.com/mdroth/linux/commit/a889a2dd64b62d9c3bf74cf02e7d8d71c7061667

and dropped the patch that reworks arch/x86/coco/Makefile.

Thanks,

Mike

> 
> The CC_PLATFORM thing is a way to check for confidential computing guest
> features by abstracting the capabilities so that you don't have to check
> *each* and *every* conf guest type in the conditionals and thus go nuts.
> 
> Thx.
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette