From: Christoph Hellwig <hch@lst.de>
To: David Rientjes <rientjes@google.com>
Cc: Jens Axboe <axboe@kernel.dk>,
Tom Lendacky <thomas.lendacky@amd.com>,
Brijesh Singh <brijesh.singh@amd.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Ming Lei <ming.lei@redhat.com>,
iommu@lists.linux-foundation.org, Peter Gonda <pgonda@google.com>,
Christoph Hellwig <hch@lst.de>, Jianxiong Gao <jxgao@google.com>
Subject: Re: [bug] __blk_mq_run_hw_queue suspicious rcu usage
Date: Thu, 5 Sep 2019 08:06:27 +0200 [thread overview]
Message-ID: <20190905060627.GA1753@lst.de> (raw)
In-Reply-To: <alpine.DEB.2.21.1909041434580.160038@chino.kir.corp.google.com>
On Wed, Sep 04, 2019 at 02:40:44PM -0700, David Rientjes wrote:
> Hi Christoph, Jens, and Ming,
>
> While booting a 5.2 SEV-enabled guest we have encountered the following
> WARNING that is followed up by a BUG because we are in atomic context
> while trying to call set_memory_decrypted:
Well, this really is a x86 / DMA API issue unfortunately. Drivers
are allowed to do GFP_ATOMIC dma allocation under locks / rcu critical
sections and from interrupts. And it seems like the SEV case can't
handle that. We have some semi-generic code to have a fixed sized
pool in kernel/dma for non-coherent platforms that have similar issues
that we could try to wire up, but I wonder if there is a better way
to handle the issue, so I've added Tom and the x86 maintainers.
Now independent of that issue using DMA coherent memory for the nvme
PRPs/SGLs doesn't actually feel very optional. We could do with
normal kmalloc allocations and just sync it to the device and back.
I wonder if we should create some general mempool-like helpers for that.
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next parent reply other threads:[~2019-09-05 6:06 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <alpine.DEB.2.21.1909041434580.160038@chino.kir.corp.google.com>
2019-09-05 6:06 ` Christoph Hellwig [this message]
2019-09-05 22:37 ` [bug] __blk_mq_run_hw_queue suspicious rcu usage David Rientjes via iommu
2019-09-16 23:45 ` David Rientjes via iommu
2019-09-17 18:23 ` David Rientjes via iommu
2019-09-17 18:32 ` Jens Axboe
2019-09-17 18:41 ` Lendacky, Thomas
2019-09-18 13:22 ` Christoph Hellwig
2019-11-27 22:11 ` David Rientjes via iommu
2019-11-28 6:40 ` Christoph Hellwig
2019-12-13 0:07 ` David Rientjes via iommu
2019-12-13 9:33 ` David Rientjes via iommu
2019-12-15 5:38 ` David Rientjes via iommu
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