On 05/03/2021 16:32, Robin Murphy wrote:
In converting intel-iommu over to the common IOMMU DMA ops, it quietly lost the functionality of its "forcedac" option. Since this is a handy thing both for testing and for performance optimisation on certain platforms, reimplement it under the common IOMMU parameter namespace.For the sake of fixing the inadvertent breakage of the Intel-specific parameter, remove the dmar_forcedac remnants and hook it up as an alias while documenting the transition to the new common parameter. Fixes: c588072bba6b ("iommu/vt-d: Convert intel iommu driver to the iommu ops") Signed-off-by: Robin Murphy <robin.mur...@arm.com>
If it's worth anything: Reviewed-by: John Garry <john.ga...@huawei.com>
--- Documentation/admin-guide/kernel-parameters.txt | 15 ++++++++------- drivers/iommu/dma-iommu.c | 13 ++++++++++++- drivers/iommu/intel/iommu.c | 5 ++--- include/linux/dma-iommu.h | 2 ++ 4 files changed, 24 insertions(+), 11 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 04545725f187..835f810f2f26 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1869,13 +1869,6 @@ bypassed by not enabling DMAR with this option. In this case, gfx device will use physical address for DMA. - forcedac [X86-64] - With this option iommu will not optimize to look - for io virtual address below 32-bit forcing dual - address cycle on pci bus for cards supporting greater - than 32-bit addressing. The default is to look - for translation below 32-bit and if not available - then look in the higher range. strict [Default Off] With this option on every unmap_single operation will result in a hardware IOTLB flush operation as opposed @@ -1964,6 +1957,14 @@ nobypass [PPC/POWERNV] Disable IOMMU bypass, using IOMMU for PCI devices.+ iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices.+ Format: { "0" | "1" } + 0 - Try to allocate a 32-bit DMA address first, before + falling back to the full range if needed. + 1 - Allocate directly from the full usable range, + forcing Dual Address Cycle for PCI cards supporting + greater than 32-bit addressing. + iommu.strict= [ARM64] Configure TLB invalidation behaviour Format: { "0" | "1" } 0 - Lazy mode. diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c index 9ab6ee22c110..260bf3de1992 100644 --- a/drivers/iommu/dma-iommu.c +++ b/drivers/iommu/dma-iommu.c @@ -52,6 +52,17 @@ struct iommu_dma_cookie { };static DEFINE_STATIC_KEY_FALSE(iommu_deferred_attach_enabled);+bool iommu_dma_forcedac __read_mostly; + +static int __init iommu_dma_forcedac_setup(char *str) +{ + int ret = kstrtobool(str, &iommu_dma_forcedac); + + if (!ret && iommu_dma_forcedac) + pr_info("Forcing DAC for PCI devices\n");
I seem to remember some disagreement on this sort of print some other time :)
+ return ret; +} +early_param("iommu.forcedac", iommu_dma_forcedac_setup);void iommu_dma_free_cpu_cached_iovas(unsigned int cpu,struct iommu_domain *domain) @@ -438,7 +449,7 @@ static dma_addr_t iommu_dma_alloc_iova(struct iommu_domain *domain, dma_limit = min(dma_limit, (u64)domain->geometry.aperture_end);
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