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Date: Tue, 25 Aug 2020 11:13:06 +0800 From: Lu Baolu <baolu.lu@...ux.intel.com> To: Chris Wilson <chris@...is-wilson.co.uk>, David Woodhouse <dwmw2@...radead.org>, Joerg Roedel <joro@...tes.org> Cc: baolu.lu@...ux.intel.com, ashok.raj@...el.com, jacob.jun.pan@...el.com, kevin.tian@...el.com, jamessewart@...sta.com, tmurphy@...sta.com, dima@...sta.com, sai.praneeth.prakhya@...el.com, iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v4 07/15] iommu/vt-d: Delegate the dma domain to upper layer Hi Chris, On 8/24/20 4:35 PM, Chris Wilson wrote: > Quoting Lu Baolu (2020-08-24 07:31:23) >> Hi Chris, >> >> On 2020/8/22 2:33, Chris Wilson wrote: >>> Quoting Lu Baolu (2019-05-25 06:41:28) >>>> This allows the iommu generic layer to allocate a dma domain and >>>> attach it to a device through the iommu api's. With all types of >>>> domains being delegated to upper layer, we can remove an internal >>>> flag which was used to distinguish domains mananged internally or >>>> externally. >>> >>> I'm seeing some really strange behaviour with this patch on a 32b >>> Skylake system (and still present on mainline). Before this patch >>> everything is peaceful and appears to work correctly. Applying this patch, >>> and we fail to initialise the GPU with a few DMAR errors reported, e.g. >>> >>> [ 20.279445] DMAR: DRHD: handling fault status reg 3 >>> [ 20.279508] DMAR: [DMA Read] Request device [00:02.0] fault addr 8900a000 [fault reason 05] PTE Write access is not set >>> >>> Setting an identity map for the igfx made the DMAR errors disappear, but >>> the GPU still failed to initialise. >>> >>> There's no difference in the DMAR configuration dmesg between working and >>> the upset patch. And the really strange part is that switching to a 64b >>> kernel with this patch, it's working. >>> >>> Any suggestions on what I should look for? >> >> Can the patch titled "[PATCH] iommu/intel: Handle 36b addressing for >> x86-32" solve this problem? > > It does. Not sure why, but that mystery I can leave for others. It's caused by left switching 36 bits operation against a 32-bit integer. Your patch fixes this by converting the integer from unsigned long to u64. It looks good to me. Thanks! > -Chris > Best regards, baolu
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