iommu: Express DMA strictness via the domain type

Eliminate the iommu_get_dma_strict() indirection and pipe the
information through the domain type from the beginning. Besides
the flow simplification this also has several nice side-effects:

 - Automatically implies strict mode for untrusted devices by
   virtue of their IOMMU_DOMAIN_DMA override.
 - Ensures that we only end up using flush queues for drivers
   which are aware of them and can actually benefit.
 - Allows us to handle flush queue init failure by falling back
   to strict mode instead of leaving it to possibly blow up later.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/47083d69155577f1367877b1594921948c366eb3.1628682049.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 17ac3dd..b7ae855 100644 (file)
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -370,13 +370,15 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
 
        init_iova_domain(iovad, 1UL << order, base_pfn);
 
-       if (!cookie->fq_domain && !dev_is_untrusted(dev) &&
-           domain->ops->flush_iotlb_all && !iommu_get_dma_strict(domain)) {
+       /* If the FQ fails we can simply fall back to strict mode */
+       if (domain->type == IOMMU_DOMAIN_DMA_FQ && !cookie->fq_domain) {
                if (init_iova_flush_queue(iovad, iommu_dma_flush_iotlb_all,
-                                         iommu_dma_entry_dtor))
+                                         iommu_dma_entry_dtor)) {
                        pr_warn("iova flush queue initialization failed\n");
-               else
+                       domain->type = IOMMU_DOMAIN_DMA;
+               } else {
                        cookie->fq_domain = domain;
+               }
        }
 
        return iova_reserve_iommu_regions(dev, domain);

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 17d6728..e09f0d4 100644 (file)
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -136,6 +136,9 @@ static int __init iommu_subsys_init(void)
                }
        }
 
+       if (!iommu_default_passthrough() && !iommu_dma_strict)
+               iommu_def_domain_type = IOMMU_DOMAIN_DMA_FQ;
+
        pr_info("Default domain type: %s %s\n",
                iommu_domain_type_str(iommu_def_domain_type),
                (iommu_cmd_line & IOMMU_CMD_LINE_DMA_API) ?
@@ -355,17 +358,10 @@ early_param("iommu.strict", iommu_dma_setup);
 void iommu_set_dma_strict(void)
 {
        iommu_dma_strict = true;
+       if (iommu_def_domain_type == IOMMU_DOMAIN_DMA_FQ)
+               iommu_def_domain_type = IOMMU_DOMAIN_DMA;
 }
 
-bool iommu_get_dma_strict(struct iommu_domain *domain)
-{
-       /* only allow lazy flushing for DMA domains */
-       if (domain->type == IOMMU_DOMAIN_DMA)
-               return iommu_dma_strict;
-       return true;
-}
-EXPORT_SYMBOL_GPL(iommu_get_dma_strict);
-
 static ssize_t iommu_group_attr_show(struct kobject *kobj,
                                     struct attribute *__attr, char *buf)
 {

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 5629ae4..923a8d1 100644 (file)
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -504,7 +504,6 @@ int iommu_set_pgtable_quirks(struct iommu_domain *domain,
                unsigned long quirks);
 
 void iommu_set_dma_strict(void);
-bool iommu_get_dma_strict(struct iommu_domain *domain);
 
 extern int report_iommu_fault(struct iommu_domain *domain, struct device *dev,
                              unsigned long iova, int flags);