Re: [PATCH v4 5/9] iommu/vt-d: Don't switch off swiotlb if use direct dma

From: Lu Baolu
Date: Tue Jun 11 2019 - 22:15:42 EST


On 6/10/19 11:54 PM, Konrad Rzeszutek Wilk wrote:
On Mon, Jun 03, 2019 at 09:16:16AM +0800, Lu Baolu wrote:
The direct dma implementation depends on swiotlb. Hence, don't
switch of swiotlb since direct dma interfaces are used in this




But I think you really want to leave the code as is but change
the #ifdef to check for IOMMU_BOUNCE_PAGE and not CONFIG_SWIOTLB.

As one could disable IOMMU_BOUNCE_PAGE.

SWIOTLB is not only used when IOMMU_BOUCE_PAGE is enabled.

Please check this code:

static dma_addr_t intel_map_page(struct device *dev, struct page *page,
unsigned long offset, size_t size,
enum dma_data_direction dir,
unsigned long attrs)
if (iommu_need_mapping(dev))
return __intel_map_single(dev, page_to_phys(page) + offset,
size, dir, *dev->dma_mask);
return dma_direct_map_page(dev, page, offset, size, dir, attrs);

The dma_direct_map_page() will eventually call swiotlb_map() if the
buffer is beyond the address capability of the device.

Best regards,

Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
Cc: Mika Westerberg <mika.westerberg@xxxxxxxxx>
Signed-off-by: Lu Baolu <>
drivers/iommu/intel-iommu.c | 6 ------
1 file changed, 6 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index d5a6c8064c56..235837c50719 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4625,9 +4625,6 @@ 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;
no_iommu = 0;
return 1;
@@ -4765,9 +4762,6 @@ int __init intel_iommu_init(void)
-#if defined(CONFIG_X86) && defined(CONFIG_SWIOTLB)
- swiotlb = 0;
dma_ops = &intel_dma_ops;