[PATCH v8 5/7] iommu/vt-d: Don't switch off swiotlb if bounce page is used

Lu Baolu
2019-08-30T07:19:08Z

The bounce page implementation depends on swiotlb. Hence, don't
switch off swiotlb if the system has untrusted devices or could
potentially be hot-added with any untrusted devices.

Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
drivers/iommu/Kconfig | 1 +
drivers/iommu/intel-iommu.c | 32 +++++++++++++++++---------------
2 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index e15cdcd8cb3c..a4ddeade8ac4 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -182,6 +182,7 @@ config INTEL_IOMMU
select IOMMU_IOVA
select NEED_DMA_MAP_STATE
select DMAR_TABLE
+ select SWIOTLB
help
DMA remapping (DMAR) devices support enables independent address
translations for Direct Memory Access (DMA) from devices.
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index fee5dff16e95..eb2a13e39eca 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4575,22 +4575,20 @@ const struct attribute_group *intel_iommu_groups[] = {
NULL,
};

-static int __init platform_optin_force_iommu(void)
+static inline bool has_untrusted_dev(void)
{
struct pci_dev *pdev = NULL;
- bool has_untrusted_dev = false;

- if (!dmar_platform_optin() || no_platform_optin)
- return 0;
+ for_each_pci_dev(pdev)
+ if (pdev->untrusted)
+ return true;

- for_each_pci_dev(pdev) {
- if (pdev->untrusted) {
- has_untrusted_dev = true;
- break;
- }
- }
+ return false;
+}

- if (!has_untrusted_dev)
+static int __init platform_optin_force_iommu(void)
+{
+ if (!dmar_platform_optin() || no_platform_optin || !has_untrusted_dev())
return 0;

if (no_iommu || dmar_disabled)
@@ -4604,9 +4602,6 @@ static int __init platform_optin_force_iommu(void)
iommu_identity_mapping |= IDENTMAP_ALL;

dmar_disabled = 0;
-#if defined(CONFIG_X86) && defined(CONFIG_SWIOTLB)
- swiotlb = 0;
-#endif
no_iommu = 0;

return 1;
@@ -4746,7 +4741,14 @@ int __init intel_iommu_init(void)
up_write(&dmar_global_lock);

#if defined(CONFIG_X86) && defined(CONFIG_SWIOTLB)
- swiotlb = 0;
+ /*
+ * 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;

--
2.17.1