On 2016年07月07日 00:00, Joerg Roedel wrote:
From: Joerg Roedel <jroe...@suse.de>
There is a race condition in the AMD IOMMU init code that
causes requested unity mappings to be blocked by the IOMMU
for a short period of time. This results on boot failures
and IO_PAGE_FAULTs on some machines.
Fix this by making sure the unity mappings are installed
before all other DMA is blocked.
Fixes: aafd8ba0ca74 ('iommu/amd: Implement add_device and remove_device')
Cc: sta...@vger.kernel.org # v4.2+
Signed-off-by: Joerg Roedel <jroe...@suse.de>
---
drivers/iommu/amd_iommu_init.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
index d091def..59741ea 100644
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -1568,13 +1568,23 @@ static int __init amd_iommu_init_pci(void)
break;
}
+ /*
+ * Order is important here to make sure any unity map requirements are
+ * fulfilled. The unity mappings are created and written to the device
+ * table during the amd_iommu_init_api() call.
+ *
+ * After that we call init_device_table_dma() to make sure any
+ * uninitialized DTE will block DMA, and in the end we flush the caches
+ * of all IOMMUs to make sure the changes to the device table are
+ * active.
+ */
Joerg,
Do you mean we need enable the V and TV bits to DTE entry after all DTEs
tables were initialized completely?
I checked this function 'init_device_table_dma', and find it just set
V and TV bit, to set translation info valid and DTE bits127:1 valid.
So I just think all things it should to do are to allow DMA access,
GPA-to-SPA translation should be active, why you add function comments
below is to not allow DMA access and suppress all page faults?
/*
* Init the device table to not allow DMA access for devices and
* suppress all page faults
*/
static void init_device_table_dma(void)
+ ret = amd_iommu_init_api();
+
init_device_table_dma();
for_each_iommu(iommu)
iommu_flush_all_caches(iommu);
- ret = amd_iommu_init_api();
-
if (!ret)
print_iommu_info();