linux-kernel - Re: [RFCv2 00/13] TDX and guest memory unmapping

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Message-ID: <20210416164602.GN2531743@casper.infradead.org>
Date:   Fri, 16 Apr 2021 17:46:02 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "Kleen, Andi" <andi.kleen@...el.com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Steve Rutherford <srutherford@...gle.com>,
        Peter Gonda <pgonda@...gle.com>,
        David Hildenbrand <david@...hat.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFCv2 00/13] TDX and guest memory unmapping

On Fri, Apr 16, 2021 at 06:40:53PM +0300, Kirill A. Shutemov wrote:
> TDX integrity check failures may lead to system shutdown host kernel must
> not allow any writes to TD-private memory. This requirment clashes with
> KVM design: KVM expects the guest memory to be mapped into host userspace
> (e.g. QEMU).
> 
> This patchset aims to start discussion on how we can approach the issue.
> 
> The core of the change is in the last patch. Please see more detailed
> description of the issue and proposoal of the solution there.

This seems to have some parallels with s390's arch_make_page_accessible().
Is there any chance to combine the two, so we don't end up with duplicated
hooks all over the MM for this kind of thing?

https://patchwork.kernel.org/project/kvm/cover/20200214222658.12946-1-borntraeger@de.ibm.com/

and recent THP/Folio-related discussion:
https://lore.kernel.org/linux-mm/20210409194059.GW2531743@casper.infradead.org/