Messages in this thread Patch in this message | | | From | Lu Baolu <> | Subject | [PATCH 3/6] iommu/vt-d: Don't force 32bit devices to uses DMA domain | Date | Sat, 7 Mar 2020 14:20:11 +0800 |
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Currently, if a 32bit device initially uses an identity domain, Intel IOMMU driver will convert it forcibly to a DMA one if its address capability is not enough for the whole system memory. The motivation was to overcome the overhead caused by possible bounced buffer.
Unfortunately, this improvement has led to many problems. For example, some 32bit devices are required to use an identity domain, forcing them to use DMA domain will cause the device not to work anymore. On the other hand, the VMD sub-devices share a domain but each sub-device might have different address capability. Forcing a VMD sub-device to use DMA domain blindly will impact the operation of other sub-devices without any notification. Further more, PCI aliased devices (PCI bridge and all devices beneath it, VMD devices and various devices quirked with pci_add_dma_alias()) must use the same domain. Forcing one device to switch to DMA domain during runtime will cause in-fligh DMAs for other devices to abort or target to other memory which might cause undefind system behavior.
Cc: Daniel Drake <drake@endlessm.com> Cc: Derrick Jonathan <jonathan.derrick@intel.com> Cc: Jerry Snitselaar <jsnitsel@redhat.com> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> --- drivers/iommu/intel-iommu.c | 46 +------------------------------------ 1 file changed, 1 insertion(+), 45 deletions(-)
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c index 33593fea0250..c58ced848206 100644 --- a/drivers/iommu/intel-iommu.c +++ b/drivers/iommu/intel-iommu.c @@ -3582,47 +3582,13 @@ static struct dmar_domain *get_private_domain_for_dev(struct device *dev) /* Check if the dev needs to go through non-identity map and unmap process.*/ static bool iommu_need_mapping(struct device *dev) { - int ret; - 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; - - if (dev->coherent_dma_mask && dev->coherent_dma_mask < dma_mask) - dma_mask = dev->coherent_dma_mask; - - if (dma_mask >= dma_direct_get_required_mask(dev)) - return false; - - /* - * 32 bit DMA is removed from si_domain and fall back to - * non-identity mapping. - */ - dmar_remove_one_dev_info(dev); - ret = iommu_request_dma_domain_for_dev(dev); - if (ret) { - struct iommu_domain *domain; - struct dmar_domain *dmar_domain; - - domain = iommu_get_domain_for_dev(dev); - if (domain) { - dmar_domain = to_dmar_domain(domain); - dmar_domain->flags |= DOMAIN_FLAG_LOSE_CHILDREN; - } - dmar_remove_one_dev_info(dev); - get_private_domain_for_dev(dev); - } - - dev_info(dev, "32bit DMA uses non-identity mapping\n"); - } - - return true; + return !identity_mapping(dev); } static dma_addr_t __intel_map_single(struct device *dev, phys_addr_t paddr, @@ -5179,16 +5145,6 @@ int __init intel_iommu_init(void) } up_write(&dmar_global_lock); -#if defined(CONFIG_X86) && defined(CONFIG_SWIOTLB) - /* - * If the system has no untrusted device or the user has decided - * to disable the bounce page mechanisms, we don't need swiotlb. - * Mark this and the pre-allocated bounce pages will be released - * later. - */ - if (!has_untrusted_dev() || intel_no_bounce) - swiotlb = 0; -#endif dma_ops = &intel_dma_ops; init_iommu_pm_ops(); -- 2.17.1
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