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Date:   Wed, 11 Aug 2021 06:52:57 +0100
From:   Christoph Hellwig <hch@infradead.org>
To:     Tom Lendacky <thomas.lendacky@amd.com>
Cc:     Baoquan He <bhe@redhat.com>, Robin Murphy <robin.murphy@arm.com>,
        Christoph Hellwig <hch@infradead.org>, brijesh.singh@amd.com,
        x86@kernel.org, kexec@lists.infradead.org,
        linux-kernel@vger.kernel.org, rppt@linux.ibm.com,
        linux-mm@kvack.org, iommu@lists.linux-foundation.org,
        rientjes@google.com
Subject: Re: [PATCH RFC 0/2] dma-pool: allow user to disable atomic pool
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References: <20210624052010.5676-1-bhe@redhat.com>
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On Tue, Aug 10, 2021 at 03:52:25PM -0500, Tom Lendacky via iommu wrote:
> I think the atomic pool is used by the NVMe driver. My understanding is
> that driver will do a dma_alloc_coherent() from interrupt context, so it
> needs to use GFP_ATOMIC. The pool was created because dma_alloc_coherent()
> would perform a set_memory_decrypted() call, which can sleep. The pool
> eliminates that issue (David can correct me if I got that wrong).

Not just the NVMe driver.  We have plenty of drivers doing that, just
do a quick grep for dma_alloc_* dma_poll_alloc, dma_pool_zalloc with
GFP_ATOMIC (and that won't even find multi-line strings).