From: Jens Axboe <axboe@kernel.dk>
To: David Rientjes <rientjes@google.com>,
Christoph Hellwig <hch@lst.de>, Keith Busch <kbusch@kernel.org>
Cc: 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>,
Jianxiong Gao <jxgao@google.com>
Subject: Re: [bug] __blk_mq_run_hw_queue suspicious rcu usage
Date: Tue, 17 Sep 2019 12:32:45 -0600 [thread overview]
Message-ID: <4cd700ef-f2fc-2bb5-35d2-0b2194accc45@kernel.dk> (raw)
In-Reply-To: <alpine.DEB.2.21.1909171121300.151243@chino.kir.corp.google.com>
On 9/17/19 12:23 PM, David Rientjes wrote:
> On Mon, 16 Sep 2019, David Rientjes wrote:
>
>> Brijesh and Tom, we currently hit this any time we boot an SEV enabled
>> Ubuntu 18.04 guest; I assume that guest kernels, especially those of such
>> major distributions, are expected to work with warnings and BUGs when
>> certain drivers are enabled.
>>
>> If the vmap purge lock is to remain a mutex (any other reason that
>> unmapping aliases can block?) then it appears that allocating a dmapool
>> is the only alternative. Is this something that you'll be addressing
>> generically or do we need to get buy-in from the maintainers of this
>> specific driver?
>>
>
> We've found that the following applied on top of 5.2.14 suppresses the
> warnings.
>
> Christoph, Keith, Jens, is this something that we could do for the nvme
> driver? I'll happily propose it formally if it would be acceptable.
No, this is not going to be acceptable, I'm afraid. This tells blk-mq
that the driver always needs blocking context for queueing IO, which
will increase latencies for the cases where we'd otherwise issue IO
directly from the context that queues it.
--
Jens Axboe
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next prev parent reply other threads:[~2019-09-17 18:32 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 ` [bug] __blk_mq_run_hw_queue suspicious rcu usage Christoph Hellwig
2019-09-05 22:37 ` 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 [this message]
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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