linux-kernel - Re: [PATCH v1 2/4] mm/mmu_notifier: drop owner from MMU_NOTIFY

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: <10e0b904-1ddb-429e-bcfa-22b360a841b3@redhat.com>
Date: Thu, 30 Jan 2025 16:26:49 +0100
From: David Hildenbrand <david@...hat.com>
To: Alistair Popple <apopple@...dia.com>, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 linux-mm@...ck.org, nouveau@...ts.freedesktop.org,
 Andrew Morton <akpm@...ux-foundation.org>, Jérôme Glisse
 <jglisse@...hat.com>, Jonathan Corbet <corbet@....net>,
 Alex Shi <alexs@...nel.org>, Yanteng Si <si.yanteng@...ux.dev>,
 Karol Herbst <kherbst@...hat.com>, Lyude Paul <lyude@...hat.com>,
 Danilo Krummrich <dakr@...nel.org>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, "Liam R. Howlett"
 <Liam.Howlett@...cle.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
 Pasha Tatashin <pasha.tatashin@...een.com>, Peter Xu <peterx@...hat.com>,
 Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [PATCH v1 2/4] mm/mmu_notifier: drop owner from
 MMU_NOTIFY_EXCLUSIVE

On 30.01.25 14:29, Simona Vetter wrote:
> On Thu, Jan 30, 2025 at 10:28:00AM +0100, David Hildenbrand wrote:
>> On 30.01.25 06:34, Alistair Popple wrote:
>>> Looking at hmm_test I see that doesn't use the sequence counter to ensure
>>> the PTE remains valid whilst it is mapped. I think that is probably wrong, so
>>> apologies if that lead you astray.
>>
>> Yes, the hmm_test does not completely follow the same model the nouveau
>> implementation does; so it might not be completely correct.
> 
> But unrelated but just crossed my mind:
> 
> I guess another crucial difference is that the hw (probably, not sure)
> will restart the fault if we don't repair it to its liking. So the
> hmm-test does need some kind of retry loop too somewhere to match that.

Yes. Especially for the folio lock spinning is a rather suboptimal 
approach. So we likely would want the option to just lock it instead of 
try-locking it. (or getting rid of it entirely :) )

> But might be good to also still land some of the other improvements
> discussed in these threads to make make_device_exclusive a bit more
> reliable instead of relying on busy-looping throug the hw fault handler
> for everything.

Right.

-- 
Cheers,

David / dhildenb