From: Christoph Hellwig <hch@lst.de>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Ming Lei <ming.lei@redhat.com>, Christoph Hellwig <hch@lst.de>,
Hannes Reinecke <hare@suse.de>,
Hamza Mahfooz <someguy@effective-light.com>,
Dan Williams <dan.j.williams@intel.com>,
linux-block@vger.kernel.org, io-uring@vger.kernel.org,
linux-raid@vger.kernel.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org
Subject: Re: [Report] annoyed dma debug warning "cacheline tracking EEXIST, overlapping mappings aren't supported"
Date: Tue, 15 Oct 2024 06:54:13 +0200 [thread overview]
Message-ID: <20241015045413.GA18058@lst.de> (raw)
In-Reply-To: <7411ae1d-5e36-46da-99cf-c485ebdb31bc@arm.com>
On Mon, Oct 14, 2024 at 07:09:08PM +0100, Robin Murphy wrote:
>>> The only case I fully understand without looking into the details
>>> is raid1, and that will obviously map the same data multiple times
>>
>> The other cases should be concurrent DIOs on same userspace buffer.
>
> active_cacheline_insert() does already bail out for DMA_TO_DEVICE, so it
> returning -EEXIST to tickle the warning would seem to genuinely imply these
> are DMA mappings requesting to *write* the same cacheline concurrently,
> which is indeed broken in general.
Yes, active_cacheline_insert only complains for FROM_DEVICE or
BIDIRECTIONAL mappings. I can't see how raid 1 would trigger that
given that it only reads from one leg at a time.
Ming, can you look a bit more into what is happening here?
next prev parent reply other threads:[~2024-10-15 4:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-14 1:27 [Report] annoyed dma debug warning "cacheline tracking EEXIST, overlapping mappings aren't supported" Ming Lei
2024-10-14 7:23 ` Hannes Reinecke
2024-10-14 7:41 ` Christoph Hellwig
2024-10-14 7:58 ` Ming Lei
2024-10-14 18:09 ` Robin Murphy
2024-10-15 1:59 ` Ming Lei
2024-10-15 2:22 ` Dan Williams
2024-10-15 4:54 ` Christoph Hellwig [this message]
2024-10-15 7:40 ` Ming Lei
2024-10-15 7:54 ` Christoph Hellwig
2024-10-15 2:31 ` Ming Lei
2024-10-14 15:17 ` Jens Axboe
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