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Subject[PATCH v9 3/5] iommu/vt-d: Don't switch off swiotlb if bounce page is used
Date
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 e12aa73008df..34e1265bb2ad 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4576,22 +4576,20 @@ 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)
@@ -4605,9 +4603,6 @@ 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;
@@ -4747,7 +4742,14 @@ 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
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