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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
Date: Wed, 11 Aug 2021 06:52:57 +0100	[thread overview]
Message-ID: <YRNluS1qt1YL2r7p@infradead.org> (raw)
In-Reply-To: <5df93c4e-ffdd-88c5-db4a-1a09826d047a@amd.com>

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).

      parent reply	other threads:[~2021-08-11  5:54 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-24  5:20 Baoquan He
2021-06-24  5:20 ` [PATCH 1/2] docs: kernel-parameters: Update to reflect the current default size of " Baoquan He
2021-06-24  5:20 ` [PATCH 2/2] dma-pool: allow user to disable " Baoquan He
2021-06-24  7:40 ` [PATCH RFC 0/2] " Christoph Hellwig
2021-06-24  9:29   ` Baoquan He
2021-06-24 10:47     ` Robin Murphy
2021-06-24 12:10       ` Christoph Hellwig
2021-08-05  6:54       ` Baoquan He
2021-08-10 20:52         ` Tom Lendacky
2021-08-11  2:23           ` Baoquan He
2021-08-11 13:46             ` Tom Lendacky
2021-08-11  5:52           ` Christoph Hellwig [this message]

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