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Tue, 21 Apr 2026 07:02:53 -0700 (PDT) Received: from [192.168.1.150] ([198.8.77.157]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7dcc712b4easm4501507a34.23.2026.04.21.07.02.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Apr 2026 07:02:52 -0700 (PDT) Message-ID: <023f90bc-9058-461d-bd68-956665ceed6d@kernel.dk> Date: Tue, 21 Apr 2026 08:02:51 -0600 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] io_uring: take page references for NOMMU pbuf_ring mmaps To: Greg Kroah-Hartman Cc: io-uring@vger.kernel.org References: <2026042115-body-attention-d15b@gregkh> <842a9dff-b12c-4cec-bc8d-8c1adb3ba280@kernel.dk> <2026042108-fiscally-unglazed-56c7@gregkh> Content-Language: en-US From: Jens Axboe In-Reply-To: <2026042108-fiscally-unglazed-56c7@gregkh> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/21/26 7:55 AM, Greg Kroah-Hartman wrote: > On Tue, Apr 21, 2026 at 07:50:32AM -0600, Jens Axboe wrote: >> On 4/21/26 7:46 AM, Greg Kroah-Hartman wrote: >>> Note, I have no way of testing this, I'm only forwarding this on because >>> I got the bug report and was able to generate something that "seems" >> >> AI bug report I presume? Because I can't imagine anyone ever attempted >> to run this. > > Yes, I got a bunch of "non-mmu" bug reports, which is a bit odd but I > guess you can do that with qemu these days? I should dig into that, > maybe that way I can test this and get a reproducer for you. If not, > let's just bin the thing. Was just pondering if I can run it in qemu. I'll take a look. But I knew it'd be some kind of AI bs, because why else would anyone look at nommu in the first place. But we have it in the codebase, so... >>> correct, but it might be a total load of crap here, my knowledge of the >>> vm layer is very low so take this for where it is coming from (i.e. a >>> non-deterministic pattern matching system.) >>> >>> I do have another patch that just disables io_uring for !MMU systems, if >>> you want that instead? Or is this feature something that !MMU devices >>> actually care about? >> >> I mean, who really cares about !MMU in the first place, we should just >> kill that off with a passion. >> >> Let me take a closer look at this and bounce it past some vm people, my >> nommu knowledge is close to zero as it's never been relevant in my >> professional life time. Which is saying something... > > Let me try to get a reproducer going first, let's not waste any more > human time on this just yet, sorry for sending this out without that > done first... Thanks! -- Jens Axboe