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From: Christoph Hellwig <hch@lst.de>
To: David Rientjes <rientjes@google.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	"Lendacky, Thomas" <Thomas.Lendacky@amd.com>,
	"Singh, Brijesh" <brijesh.singh@amd.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Ming Lei <ming.lei@redhat.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	Peter Gonda <pgonda@google.com>, Keith Busch <kbusch@kernel.org>,
	Christoph Hellwig <hch@lst.de>, Jianxiong Gao <jxgao@google.com>
Subject: Re: [bug] __blk_mq_run_hw_queue suspicious rcu usage
Date: Thu, 28 Nov 2019 07:40:56 +0100	[thread overview]
Message-ID: <20191128064056.GA19822@lst.de> (raw)
In-Reply-To: <alpine.DEB.2.21.1911271359000.135363@chino.kir.corp.google.com>

On Wed, Nov 27, 2019 at 02:11:28PM -0800, David Rientjes wrote:
> So we're left with making dma_pool_alloc(GFP_ATOMIC) actually be atomic 
> even when the DMA needs to be unencrypted for SEV.  Christoph's suggestion 
> was to wire up dmapool in kernel/dma/remap.c for this.  Is that necessary 
> to be done for all devices that need to do dma_pool_alloc(GFP_ATOMIC) or 
> can we do it within the DMA API itself so it's transparent to the driver?

It needs to be transparent to the driver.  Lots of drivers use GFP_ATOMIC
dma allocations, and all of them are broken on SEV setups currently.
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WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: David Rientjes <rientjes@google.com>
Cc: Christoph Hellwig <hch@lst.de>,
	"Lendacky, Thomas" <Thomas.Lendacky@amd.com>,
	Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@kernel.dk>,
	"Singh, Brijesh" <brijesh.singh@amd.com>,
	Ming Lei <ming.lei@redhat.com>, Peter Gonda <pgonda@google.com>,
	Jianxiong Gao <jxgao@google.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"x86@kernel.org" <x86@kernel.org>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>
Subject: Re: [bug] __blk_mq_run_hw_queue suspicious rcu usage
Date: Thu, 28 Nov 2019 07:40:56 +0100	[thread overview]
Message-ID: <20191128064056.GA19822@lst.de> (raw)
In-Reply-To: <alpine.DEB.2.21.1911271359000.135363@chino.kir.corp.google.com>

On Wed, Nov 27, 2019 at 02:11:28PM -0800, David Rientjes wrote:
> So we're left with making dma_pool_alloc(GFP_ATOMIC) actually be atomic 
> even when the DMA needs to be unencrypted for SEV.  Christoph's suggestion 
> was to wire up dmapool in kernel/dma/remap.c for this.  Is that necessary 
> to be done for all devices that need to do dma_pool_alloc(GFP_ATOMIC) or 
> can we do it within the DMA API itself so it's transparent to the driver?

It needs to be transparent to the driver.  Lots of drivers use GFP_ATOMIC
dma allocations, and all of them are broken on SEV setups currently.

  reply	other threads:[~2019-11-28  6:41 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-04 21:40 [bug] __blk_mq_run_hw_queue suspicious rcu usage David Rientjes
2019-09-05  6:06 ` Christoph Hellwig
2019-09-05  6:06   ` Christoph Hellwig
2019-09-05 22:37   ` David Rientjes via iommu
2019-09-05 22:37     ` David Rientjes
2019-09-16 23:45     ` David Rientjes via iommu
2019-09-16 23:45       ` David Rientjes
2019-09-17 18:23       ` David Rientjes via iommu
2019-09-17 18:23         ` David Rientjes
2019-09-17 18:32         ` Jens Axboe
2019-09-17 18:32           ` Jens Axboe
2019-09-17 18:41         ` Lendacky, Thomas
2019-09-17 18:41           ` Lendacky, Thomas
2019-09-18 13:22           ` Christoph Hellwig
2019-09-18 13:22             ` Christoph Hellwig
2019-11-27 22:11             ` David Rientjes via iommu
2019-11-27 22:11               ` David Rientjes
2019-11-28  6:40               ` Christoph Hellwig [this message]
2019-11-28  6:40                 ` Christoph Hellwig
2019-12-13  0:07                 ` David Rientjes via iommu
2019-12-13  0:07                   ` David Rientjes
2019-12-13  9:33                   ` David Rientjes via iommu
2019-12-13  9:33                     ` David Rientjes
2019-12-15  5:38                   ` David Rientjes via iommu
2019-12-15  5:38                     ` David Rientjes

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