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From: Robin Murphy <robin.murphy@arm.com>
To: Jason Gunthorpe <jgg@ziepe.ca>, Niklas Schnelle <schnelle@linux.ibm.com>
Cc: Joerg Roedel <joro@8bytes.org>,
	Matthew Rosato <mjrosato@linux.ibm.com>,
	Will Deacon <will@kernel.org>,
	Wenjia Zhang <wenjia@linux.ibm.com>,
	Gerd Bayer <gbayer@linux.ibm.com>,
	Julian Ruess <julianr@linux.ibm.com>,
	Pierre Morel <pmorel@linux.ibm.com>,
	Alexandra Winter <wintera@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>,
	Christian Borntraeger <borntraeger@linux.ibm.com>,
	Sven Schnelle <svens@linux.ibm.com>,
	Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
	Hector Martin <marcan@marcan.st>, Sven Peter <sven@svenpeter.dev>,
	Alyssa Rosenzweig <alyssa@rosenzweig.io>,
	David Woodhouse <dwmw2@infradead.org>,
	Lu Baolu <baolu.lu@linux.intel.com>,
	Andy Gross <agross@kernel.org>,
	Bjorn Andersson <andersson@kernel.org>,
	Konrad Dybcio <konrad.dybcio@linaro.org>,
	Yong Wu <yong.wu@mediatek.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	AngeloGioacchino Del Regno
	<angelogioacchino.delregno@collabora.com>,
	Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
	Orson Zhai <orsonzhai@gmail.com>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	Chunyan Zhang <zhang.lyra@gmail.com>,
	Chen-Yu Tsai <wens@csie.org>,
	Jernej Skrabec <jernej.skrabec@gmail.com>,
	Samuel Holland <samuel@sholland.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	Krishna Reddy <vdumpa@nvidia.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Jonathan Corbet <corbet@lwn.net>,
	linux-s390@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, iommu@lists.linux.dev,
	asahi@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
	linux-arm-msm@vger.kernel.org,
	linux-mediatek@lists.infradead.org, linux-sunxi@lists.linux.dev,
	linux-tegra@vger.kernel.org, linux-doc@vger.kernel.org
Subject: Re: [PATCH v12 0/6] iommu/dma: s390 DMA API conversion and optimized IOTLB flushing
Date: Wed, 27 Sep 2023 17:16:23 +0100	[thread overview]
Message-ID: <96c0892f-20e6-db1f-f310-9b09d419aa6a@arm.com> (raw)
In-Reply-To: <20230927154009.GN13795@ziepe.ca>

On 27/09/2023 4:40 pm, Jason Gunthorpe wrote:
> On Wed, Sep 27, 2023 at 05:24:20PM +0200, Niklas Schnelle wrote:
> 
>> Ok, another update. On trying it out again this problem actually also
>> occurs when applying this v12 on top of v6.6-rc3 too. Also I guess
>> unlike my prior thinking it probably doesn't occur with
>> iommu.forcedac=1 since that still allows IOVAs below 4 GiB and we might
>> be the only ones who don't support those. From my point of view this
>> sounds like a mlx5_core issue they really should call
>> dma_set_mask_and_coherent() before their first call to
>> dma_alloc_coherent() not after. So I guess I'll send a v13 of this
>> series rebased on iommu/core and with an additional mlx5 patch and then
>> let's hope we can get that merged in a way that doesn't leave us with
>> broken ConnectX VFs for too long.
> 
> Yes, OK. It definitely sounds wrong that mlx5 is doing dma allocations before
> setting it's dma_set_mask_and_coherent(). Please link to this thread
> and we can get Leon or Saeed to ack it for Joerg.
> 
> (though wondering why s390 is the only case that ever hit this?)

Probably because most systems happen to be able to satisfy the 
allocation within the default 32-bit mask - the whole bottom 4GB of IOVA 
space being reserved is pretty atypical.

TBH it makes me wonder the opposite - how this ever worked on s390 
before? And I think the answer to that is "by pure chance", since upon 
inspection the existing s390_pci_dma_ops implementation appears to pay 
absolutely no attention to the device's DMA masks whatsoever :(

Robin.

  reply	other threads:[~2023-09-27 16:16 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-25 10:11 [PATCH v12 0/6] iommu/dma: s390 DMA API conversion and optimized IOTLB flushing Niklas Schnelle
2023-08-25 10:11 ` [PATCH v12 1/6] iommu: Allow .iotlb_sync_map to fail and handle s390's -ENOMEM return Niklas Schnelle
2023-08-25 10:11 ` [PATCH v12 2/6] s390/pci: prepare is_passed_through() for dma-iommu Niklas Schnelle
2023-08-25 10:11 ` [PATCH v12 3/6] s390/pci: Use dma-iommu layer Niklas Schnelle
2023-08-25 10:11 ` [PATCH v12 4/6] iommu/s390: Disable deferred flush for ISM devices Niklas Schnelle
2023-08-25 18:23   ` Matthew Rosato
2023-08-25 10:11 ` [PATCH v12 5/6] iommu/dma: Allow a single FQ in addition to per-CPU FQs Niklas Schnelle
2023-09-11 12:06   ` Niklas Schnelle
2023-08-25 10:11 ` [PATCH v12 6/6] iommu/dma: Use a large flush queue and timeout for shadow_on_flush Niklas Schnelle
2023-08-25 18:26 ` [PATCH v12 0/6] iommu/dma: s390 DMA API conversion and optimized IOTLB flushing Matthew Rosato
2023-09-05 16:09   ` Robin Murphy
2023-09-25  9:56 ` Joerg Roedel
2023-09-26 15:04 ` Joerg Roedel
2023-09-26 16:08   ` Jason Gunthorpe
2023-09-27  8:55     ` Niklas Schnelle
2023-09-27  9:26       ` Robin Murphy
2023-09-27  9:55       ` Joerg Roedel
2023-09-27 11:24         ` Niklas Schnelle
2023-09-27 13:20           ` Niklas Schnelle
2023-09-27 14:31             ` Niklas Schnelle
2023-09-27 15:24               ` Niklas Schnelle
2023-09-27 15:40                 ` Jason Gunthorpe
2023-09-27 16:16                   ` Robin Murphy [this message]
2023-09-27 20:25                   ` Matthew Rosato

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