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Date: Mon, 19 Jul 2021 14:07:43 +0100
From: Matthew Wilcox <willy@infradead.org>
To: Joerg Roedel <jroedel@suse.de>
Cc: David Rientjes <rientjes@google.com>, Borislav Petkov <bp@alien8.de>,
	Andy Lutomirski <luto@kernel.org>,
	Sean Christopherson <seanjc@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Andi Kleen <ak@linux.intel.com>,
	Brijesh Singh <brijesh.singh@amd.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Jon Grimm <jon.grimm@amd.com>, Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Paolo Bonzini <pbonzini@redhat.com>, Ingo Molnar <mingo@redhat.com>,
	"Kaplan, David" <David.Kaplan@amd.com>,
	Varad Gautam <varad.gautam@suse.com>,
	Dario Faggioli <dfaggioli@suse.com>, x86@kernel.org,
	linux-mm@kvack.org, linux-coco@lists.linux.dev
Subject: Re: Runtime Memory Validation in Intel-TDX and AMD-SNP
Message-ID: <YPV5H0A+HB/t6y+z@casper.infradead.org>
References: <YPV27hDPZUoVsIZt@suse.de>
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In-Reply-To: <YPV27hDPZUoVsIZt@suse.de>

On Mon, Jul 19, 2021 at 02:58:22PM +0200, Joerg Roedel wrote:
> I'd like to get some movement again into the discussion around how to
> implement runtime memory validation for confidential guests and wrote up
> some thoughts on it.
> Below are the results in form of a proposal I put together. Please let
> me know your thoughts on it and whether it fits everyones requirements.

I think this proposal skips (intentionally?) something that s390 already
implemented: the secure guest deliberately allowing the hypervisor to
access certain pages for a period and then re-validating them.  I hope x86
can use the same interface as s390 for this, or if not, the interface can
be modified to be usable by all architectures.  See commit f28d43636d6f
("mm/gup/writeback: add callbacks for inaccessible pages").