linux-kernel - Re: [PATCH v12 0/6] iommu/dma: s390 DMA API conversion and optimized IOTLB flushing

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

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

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.