Re: [PATCH] iommu/amd: Mark translation invalid during device detach
Joerg, On 1/16/19 8:03 PM, j...@8bytes.org wrote: > Hi Suravee, > > On Wed, Jan 16, 2019 at 04:15:10AM +, Suthikulpanit, Suravee wrote: >> From: Suravee Suthikulpanit >> >> When a device switches domain, IOMMU driver detach device from the old >> domain, and attach device to the new domain. During this period >> the host table root pointer is not set, which means DMA translation >> should be marked as invalid (clear TV bit). >> >> So, clear the TV bit when detach the device. The TV bit will be set >> again when attaching device to the new domain. > > Is there a specific problem with setting the TV bit? We are not currently seeing issue. > Note that the update will clear all other fields in the first 128 bits > of the DTE, which means that IR, IW and Mode are all set to 0. This > effectivly blocks all DMA requests from the device, which is by design. Ahh.. This makes sense now. I missed the IR/IW/Mode=0 part. It was not clear to us earlier. Thanks for clarification. Regards, Suravee ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH] iommu/amd: Mark translation invalid during device detach
Hi Suravee, On Wed, Jan 16, 2019 at 04:15:10AM +, Suthikulpanit, Suravee wrote: > From: Suravee Suthikulpanit > > When a device switches domain, IOMMU driver detach device from the old > domain, and attach device to the new domain. During this period > the host table root pointer is not set, which means DMA translation > should be marked as invalid (clear TV bit). > > So, clear the TV bit when detach the device. The TV bit will be set > again when attaching device to the new domain. Is there a specific problem with setting the TV bit? Note that the update will clear all other fields in the first 128 bits of the DTE, which means that IR, IW and Mode are all set to 0. This effectivly blocks all DMA requests from the device, which is by design. Regards, Joerg ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
[PATCH] iommu/amd: Mark translation invalid during device detach
From: Suravee Suthikulpanit
When a device switches domain, IOMMU driver detach device from the old
domain, and attach device to the new domain. During this period
the host table root pointer is not set, which means DMA translation
should be marked as invalid (clear TV bit).
So, clear the TV bit when detach the device. The TV bit will be set
again when attaching device to the new domain.
Cc: Boris Ostrovsky
Signed-off-by: Brijesh Singh
Signed-off-by: Suravee Suthikulpanit
---
drivers/iommu/amd_iommu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 87ba23a75b38..525659b88ade 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -1956,7 +1956,7 @@ static void set_dte_entry(u16 devid, struct
protection_domain *domain,
static void clear_dte_entry(u16 devid)
{
/* remove entry from the device table seen by the hardware */
- amd_iommu_dev_table[devid].data[0] = DTE_FLAG_V | DTE_FLAG_TV;
+ amd_iommu_dev_table[devid].data[0] = DTE_FLAG_V;
amd_iommu_dev_table[devid].data[1] &= DTE_FLAG_MASK;
amd_iommu_apply_erratum_63(devid);
--
2.17.1
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