From: Will Deacon <will.deacon@arm.com>
To: "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
Cc: "Yang, Shunyong" <shunyong.yang@hxt-semitech.com>,
Robin Murphy <robin.murphy@arm.com>,
Jean-Philippe Brucker <jean-philippe.brucker@arm.com>,
Joerg Roedel <joro@8bytes.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
iommu <iommu@lists.linux-foundation.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 4/6] iommu/io-pgtable-arm: add support for non-strict mode
Date: Tue, 14 Aug 2018 09:35:01 +0100 [thread overview]
Message-ID: <20180814083500.GA28101@arm.com> (raw)
In-Reply-To: <5B7293E5.7040702@huawei.com>
On Tue, Aug 14, 2018 at 04:33:41PM +0800, Leizhen (ThunderTown) wrote:
> On 2018/8/6 9:32, Yang, Shunyong wrote:
> > On 2018/7/26 22:37, Robin Murphy wrote:
> >> Because DMA code is not the only caller of iommu_map/unmap. It's
> >> perfectly legal in the IOMMU API to partially unmap a previous mapping
> >> such that a block entry needs to be split. The DMA API, however, is a
> >> lot more constrined, and thus by construction the iommu-dma layer will
> >> never generate a block-splitting iommu_unmap() except as a result of
> >> illegal DMA API usage, and we obviously do not need to optimise for that
> >> (you will get a warning about mismatched unmaps under dma-debug, but
> >> it's a bit too expensive to police in the general case).
> >>
> >
> > When I was reading the code around arm_lpae_split_blk_unmap(), I was
> > curious in which scenario a block will be split. Now with your comments
> > "Because DMA code is not the only caller of iommu_map/unmap", it seems
> > depending on the user.
> >
> > Would you please explain this further? I mean besides DMA, which user
> > will use iommu_map/umap and how it split a block.
>
> I also think that arm_lpae_split_blk_unmap() scenario is not exist, maybe
> we should remove it, and give a warning for this wrong usage.
Can't it happen with VFIO?
Will
next prev parent reply other threads:[~2018-08-14 8:34 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-12 6:18 [PATCH v3 0/6] add non-strict mode support for arm-smmu-v3 Zhen Lei
2018-07-12 6:18 ` [PATCH v3 1/6] iommu/arm-smmu-v3: fix the implementation of flush_iotlb_all hook Zhen Lei
2018-07-12 6:18 ` [PATCH v3 2/6] iommu/dma: add support for non-strict mode Zhen Lei
2018-07-24 22:01 ` Robin Murphy
2018-07-26 4:15 ` Leizhen (ThunderTown)
2018-07-12 6:18 ` [PATCH v3 3/6] iommu/amd: use default branch to deal with all non-supported capabilities Zhen Lei
2018-07-12 6:18 ` [PATCH v3 4/6] iommu/io-pgtable-arm: add support for non-strict mode Zhen Lei
2018-07-24 22:25 ` Robin Murphy
2018-07-26 7:20 ` Leizhen (ThunderTown)
2018-07-26 14:35 ` Robin Murphy
2018-08-06 1:32 ` Yang, Shunyong
2018-08-14 8:33 ` Leizhen (ThunderTown)
2018-08-14 8:35 ` Will Deacon [this message]
2018-08-14 10:02 ` Robin Murphy
2018-08-15 1:43 ` Yang, Shunyong
2018-08-15 7:33 ` Will Deacon
2018-08-15 7:35 ` Will Deacon
2018-08-16 0:43 ` Yang, Shunyong
2018-07-12 6:18 ` [PATCH v3 5/6] iommu/arm-smmu-v3: " Zhen Lei
2018-07-12 6:18 ` [PATCH v3 6/6] iommu/arm-smmu-v3: add bootup option "iommu_strict_mode" Zhen Lei
2018-07-24 22:46 ` Robin Murphy
2018-07-26 7:41 ` Leizhen (ThunderTown)
2018-07-24 21:51 ` [PATCH v3 0/6] add non-strict mode support for arm-smmu-v3 Robin Murphy
2018-07-26 3:44 ` Leizhen (ThunderTown)
2018-07-26 14:16 ` Robin Murphy
2018-07-27 2:49 ` Leizhen (ThunderTown)
2018-07-27 9:37 ` Will Deacon
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