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Date: Thu, 19 Aug 2021 10:52:53 +0100
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH v2 03/12] x86/sev: Add an x86 version of prot_guest_has()
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To: Tom Lendacky <thomas.lendacky@amd.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, iommu@lists.linux-foundation.org, kvm@vger.kernel.org, linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-graphics-maintainer@vmware.com, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, Borislav Petkov <bp@alien8.de>, Brijesh Singh <brijesh.singh@amd.com>, Joerg Roedel <joro@8bytes.org>, Andi Kleen <ak@linux.intel.com>, Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@linux.intel.com>, Tianyu Lan <Tianyu.Lan@microsoft.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Dave Hansen <dave.hansen@linux.intel.com>, Andy Lutomirski <luto@kernel.org>, Peter Zijlstra <peterz@infradead.org>, Joerg Roedel <jroedel@suse.de>

On Fri, Aug 13, 2021 at 11:59:22AM -0500, Tom Lendacky wrote:
> While the name suggests this is intended mainly for guests, it will
> also be used for host memory encryption checks in place of sme_active().

Which suggest that the name is not good to start with.  Maybe protected
hardware, system or platform might be a better choice?

> +static inline bool prot_guest_has(unsigned int attr)
> +{
> +#ifdef CONFIG_AMD_MEM_ENCRYPT
> +	if (sme_me_mask)
> +		return amd_prot_guest_has(attr);
> +#endif
> +
> +	return false;
> +}

Shouldn't this be entirely out of line?

> +/* 0x800 - 0x8ff reserved for AMD */
> +#define PATTR_SME			0x800
> +#define PATTR_SEV			0x801
> +#define PATTR_SEV_ES			0x802

Why do we need reservations for a purely in-kernel namespace?

And why are you overoading a brand new generic API with weird details
of a specific implementation like this?

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