Re: [PATCH v5 4/5] iommu/dma: Pass address limit rather than size to iommu_setup_dma_ops()

Robin Murphy <robin.murphy@xxxxxxx> · Fri, 18 Jun 2021 17:29:11 +0100

On 2021-06-18 16:20, Jean-Philippe Brucker wrote:
Passing a 64-bit address width to iommu_setup_dma_ops() is valid on
virtual platforms, but isn't currently possible. The overflow check in
iommu_dma_init_domain() prevents this even when @dma_base isn't 0. Pass
a limit address instead of a size, so callers don't have to fake a size
to work around the check.

The base and limit parameters are being phased out, because:
* they are redundant for x86 callers. dma-iommu already reserves the
   first page, and the upper limit is already in domain->geometry.
* they can now be obtained from dev->dma_range_map on Arm.
But removing them on Arm isn't completely straightforward so is left for
future work. As an intermediate step, simplify the x86 callers by
passing dummy limits.

Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>

Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
---
  include/linux/dma-iommu.h   |  4 ++--
  arch/arm64/mm/dma-mapping.c |  2 +-
  drivers/iommu/amd/iommu.c   |  2 +-
  drivers/iommu/dma-iommu.c   | 12 ++++++------
  drivers/iommu/intel/iommu.c |  5 +----
  5 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h
index 6e75a2d689b4..758ca4694257 100644
--- a/include/linux/dma-iommu.h
+++ b/include/linux/dma-iommu.h
@@ -19,7 +19,7 @@ int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base);
  void iommu_put_dma_cookie(struct iommu_domain *domain);
  
  /* Setup call for arch DMA mapping code */
-void iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 size);
+void iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 dma_limit);
  
  /* The DMA API isn't _quite_ the whole story, though... */
  /*
@@ -50,7 +50,7 @@ struct msi_msg;
  struct device;
  
  static inline void iommu_setup_dma_ops(struct device *dev, u64 dma_base,
-		u64 size)
+				       u64 dma_limit)
  {
  }
  
diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index 4bf1dd3eb041..6719f9efea09 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -50,7 +50,7 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
  
  	dev->dma_coherent = coherent;
  	if (iommu)
-		iommu_setup_dma_ops(dev, dma_base, size);
+		iommu_setup_dma_ops(dev, dma_base, dma_base + size - 1);
  
  #ifdef CONFIG_XEN
  	if (xen_swiotlb_detect())
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 3ac42bbdefc6..216323fb27ef 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -1713,7 +1713,7 @@ static void amd_iommu_probe_finalize(struct device *dev)
  	/* Domains are initialized for this device - have a look what we ended up with */
  	domain = iommu_get_domain_for_dev(dev);
  	if (domain->type == IOMMU_DOMAIN_DMA)
-		iommu_setup_dma_ops(dev, IOVA_START_PFN << PAGE_SHIFT, 0);
+		iommu_setup_dma_ops(dev, 0, U64_MAX);
  	else
  		set_dma_ops(dev, NULL);
  }
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 7bcdd1205535..c62e19bed302 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -319,16 +319,16 @@ static bool dev_is_untrusted(struct device *dev)
   * iommu_dma_init_domain - Initialise a DMA mapping domain
   * @domain: IOMMU domain previously prepared by iommu_get_dma_cookie()
   * @base: IOVA at which the mappable address space starts
- * @size: Size of IOVA space
+ * @limit: Last address of the IOVA space
   * @dev: Device the domain is being initialised for
   *
- * @base and @size should be exact multiples of IOMMU page granularity to
+ * @base and @limit + 1 should be exact multiples of IOMMU page granularity to
   * avoid rounding surprises. If necessary, we reserve the page at address 0
   * to ensure it is an invalid IOVA. It is safe to reinitialise a domain, but
   * any change which could make prior IOVAs invalid will fail.
   */
  static int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
-		u64 size, struct device *dev)
+				 dma_addr_t limit, struct device *dev)
  {
  	struct iommu_dma_cookie *cookie = domain->iova_cookie;
  	unsigned long order, base_pfn;
@@ -346,7 +346,7 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
  	/* Check the domain allows at least some access to the device... */
  	if (domain->geometry.force_aperture) {
  		if (base > domain->geometry.aperture_end ||
-		    base + size <= domain->geometry.aperture_start) {
+		    limit < domain->geometry.aperture_start) {
  			pr_warn("specified DMA range outside IOMMU capability\n");
  			return -EFAULT;
  		}
@@ -1308,7 +1308,7 @@ static const struct dma_map_ops iommu_dma_ops = {
   * The IOMMU core code allocates the default DMA domain, which the underlying
   * IOMMU driver needs to support via the dma-iommu layer.
   */
-void iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 size)
+void iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 dma_limit)
  {
  	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
  
@@ -1320,7 +1320,7 @@ void iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 size)
  	 * underlying IOMMU driver needs to support via the dma-iommu layer.
  	 */
  	if (domain->type == IOMMU_DOMAIN_DMA) {
-		if (iommu_dma_init_domain(domain, dma_base, size, dev))
+		if (iommu_dma_init_domain(domain, dma_base, dma_limit, dev))
  			goto out_err;
  		dev->dma_ops = &iommu_dma_ops;
  	}
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index be35284a2016..2f7213f0e7a1 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -5165,13 +5165,10 @@ static void intel_iommu_release_device(struct device *dev)
  
  static void intel_iommu_probe_finalize(struct device *dev)
  {
-	dma_addr_t base = IOVA_START_PFN << VTD_PAGE_SHIFT;
  	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
-	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
  
  	if (domain && domain->type == IOMMU_DOMAIN_DMA)
-		iommu_setup_dma_ops(dev, base,
-				    __DOMAIN_MAX_ADDR(dmar_domain->gaw) - base);
+		iommu_setup_dma_ops(dev, 0, U64_MAX);
  	else
  		set_dma_ops(dev, NULL);
  }







