linux-kernel - Re: [RFC PATCH v11 10/29] mm: Add AS_UNMOVABLE to mark mapping as completely unmovable

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Message-ID: <6da710cf-2bc0-bb6e-26f1-fba14ca767db@redhat.com>
Date:   Fri, 28 Jul 2023 18:13:26 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vlastimil Babka <vbabka@...e.cz>,
        Matthew Wilcox <willy@...radead.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Huacai Chen <chenhuacai@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Paul Moore <paul@...l-moore.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>, kvm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Fuad Tabba <tabba@...gle.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Ackerley Tng <ackerleytng@...gle.com>,
        Maciej Szmigiero <mail@...iej.szmigiero.name>,
        David Hildenbrand <david@...hat.com>,
        Quentin Perret <qperret@...gle.com>,
        Michael Roth <michael.roth@....com>,
        Wang <wei.w.wang@...el.com>,
        Liam Merwick <liam.merwick@...cle.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>
Subject: Re: [RFC PATCH v11 10/29] mm: Add AS_UNMOVABLE to mark mapping as
 completely unmovable

On 7/28/23 18:02, Vlastimil Babka wrote:
>> There's even a comment to that effect later on in the function:
> Hmm, well spotted. But it wouldn't be so great if we now had to lock every
> inspected page (and not just dirty pages), just to check the AS_ bit.
> 
> But I wonder if this is leftover from previous versions. Are the guest pages
> even PageLRU currently? (and should they be, given how they can't be swapped
> out or anything?) If not, isolate_migratepages_block will skip them anyway.

No, they're not (migration or even swap-out is not excluded for the 
future, but for now it's left for future work.

Paolo