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Date: Tue, 18 Feb 2020 10:38:14 +0800 From: Lu Baolu <baolu.lu@...ux.intel.com> To: Joerg Roedel <joro@...tes.org>, David Woodhouse <dwmw2@...radead.org> Cc: jroedel@...e.de, iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 3/5] iommu/vt-d: Do deferred attachment in iommu_need_mapping() Hi Joerg, Thanks for doing this. On 2020/2/18 3:38, Joerg Roedel wrote: > From: Joerg Roedel <jroedel@...e.de> > > The attachment of deferred devices needs to happen before the check > whether the device is identity mapped or not. Otherwise the check will > return wrong results, cause warnings boot failures in kdump kernels, like > > WARNING: CPU: 0 PID: 318 at ../drivers/iommu/intel-iommu.c:592 domain_get_iommu+0x61/0x70 > > [...] > > Call Trace: > __intel_map_single+0x55/0x190 > intel_alloc_coherent+0xac/0x110 > dmam_alloc_attrs+0x50/0xa0 > ahci_port_start+0xfb/0x1f0 [libahci] > ata_host_start.part.39+0x104/0x1e0 [libata] > > With the earlier check the kdump boot succeeds and a crashdump is written. > > Signed-off-by: Joerg Roedel <jroedel@...e.de> > --- > drivers/iommu/intel-iommu.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c > index 42cdcce1602e..32f43695a22b 100644 > --- a/drivers/iommu/intel-iommu.c > +++ b/drivers/iommu/intel-iommu.c > @@ -2541,9 +2541,6 @@ static void do_deferred_attach(struct device *dev) > > static struct dmar_domain *deferred_attach_domain(struct device *dev) > { > - if (unlikely(attach_deferred(dev))) > - do_deferred_attach(dev); > - This should also be moved to the call place of deferred_attach_domain() in bounce_map_single(). bounce_map_single() assumes that devices always use DMA domain, so it doesn't call iommu_need_mapping(). We could do_deferred_attach() there manually. Best regards, baolu > return find_domain(dev); > } > > @@ -3595,6 +3592,9 @@ static bool iommu_need_mapping(struct device *dev) > if (iommu_dummy(dev)) > return false; > > + if (unlikely(attach_deferred(dev))) > + do_deferred_attach(dev); > + > ret = identity_mapping(dev); > if (ret) { > u64 dma_mask = *dev->dma_mask; >
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