Messages in this thread | | | Subject | Re: [PATCH] iommu/dma: Resurrect the "forcedac" option | From | Lu Baolu <> | Date | Mon, 8 Mar 2021 09:51:36 +0800 |
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Hi Robin,
On 3/6/21 12:32 AM, 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.murphy@arm.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"); > + 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); > > /* Try to get PCI devices a SAC address */ > - if (dma_limit > DMA_BIT_MASK(32) && dev_is_pci(dev)) > + if (dma_limit > DMA_BIT_MASK(32) && !iommu_dma_forcedac && dev_is_pci(dev)) > iova = alloc_iova_fast(iovad, iova_len, > DMA_BIT_MASK(32) >> shift, false); > > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c > index ee0932307d64..1c32522220bc 100644 > --- a/drivers/iommu/intel/iommu.c > +++ b/drivers/iommu/intel/iommu.c > @@ -360,7 +360,6 @@ int intel_iommu_enabled = 0; > EXPORT_SYMBOL_GPL(intel_iommu_enabled); > > static int dmar_map_gfx = 1; > -static int dmar_forcedac; > static int intel_iommu_strict; > static int intel_iommu_superpage = 1; > static int iommu_identity_mapping; > @@ -451,8 +450,8 @@ static int __init intel_iommu_setup(char *str) > dmar_map_gfx = 0; > pr_info("Disable GFX device mapping\n"); > } else if (!strncmp(str, "forcedac", 8)) { > - pr_info("Forcing DAC for PCI devices\n"); > - dmar_forcedac = 1; > + pr_warn("intel_iommu=forcedac deprecated; use iommu.forcedac instead\n"); > + iommu_dma_forcedac = true; > } else if (!strncmp(str, "strict", 6)) { > pr_info("Disable batched IOTLB flush\n"); > intel_iommu_strict = 1; > diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h > index 706b68d1359b..13d1f4c14d7b 100644 > --- a/include/linux/dma-iommu.h > +++ b/include/linux/dma-iommu.h > @@ -40,6 +40,8 @@ void iommu_dma_get_resv_regions(struct device *dev, struct list_head *list); > void iommu_dma_free_cpu_cached_iovas(unsigned int cpu, > struct iommu_domain *domain); > > +extern bool iommu_dma_forcedac; > + > #else /* CONFIG_IOMMU_DMA */ > > struct iommu_domain; >
Thanks for catching this.
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Best regards, baolu
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