linux-kernel - Re: [RFC PATCH v11 00/29] KVM: guest

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <66efd7f5-92ed-45ec-0550-ca7f012a6e63@amd.com>
Date:   Thu, 27 Jul 2023 12:12:11 +0530
From:   "Nikunj A. Dadhania" <nikunj@....com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.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>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        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>,
        Vlastimil Babka <vbabka@...e.cz>,
        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>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFC PATCH v11 00/29] KVM: guest_memfd() and per-page attributes

On 7/26/2023 7:54 PM, Sean Christopherson wrote:
> On Wed, Jul 26, 2023, Nikunj A. Dadhania wrote:
>> On 7/24/2023 10:30 PM, Sean Christopherson wrote:

>>>>   /proc/<qemu pid>/smaps
>>>>   7f528be00000-7f5c8be00000 rw-p 00000000 00:01 26629                      /memfd:memory-backend-memfd-shared (deleted)
>>>>   7f5c90200000-7f5c90220000 rw-s 00000000 00:01 44033                      /memfd:rom-backend-memfd-shared (deleted)
>>>>   7f5c90400000-7f5c90420000 rw-s 00000000 00:01 44032                      /memfd:rom-backend-memfd-shared (deleted)
>>>>   7f5c90800000-7f5c90b7c000 rw-s 00000000 00:01 1025                       /memfd:rom-backend-memfd-shared (deleted)
>>>
>>> This is all expected, and IMO correct.  There are no userspace mappings, and so
>>> not accounting anything is working as intended.
>> Doesn't sound that correct, if 10 SNP guests are running each using 10GB, how
>> would we know who is using 100GB of memory?
> 
> It's correct with respect to what the interfaces show, which is how much memory
> is *mapped* into userspace.
> 
> As I said (or at least tried to say) in my first reply, I am not against exposing
> memory usage to userspace via stats, only that it's not obvious to me that the
> existing VMA-based stats are the most appropriate way to surface this information.

Right, then should we think in the line of creating a VM IOCTL for querying current memory
usage for guest-memfd ?

We could use memcg for statistics, but then memory cgroup can be disabled and so memcg 
isn't really a dependable option.

Do you have some ideas on how to expose the memory usage to the user space other than
VMA-based stats ?

Regards,
Nikunj