4.20-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit c12b08ebbe16f0d3a96a116d86709b04c1ee8e74 ]
The parameter is still there but it's ignored. We need to check its value before deciding to go into passthrough mode for AMD IOMMU v2 capable device.
We occasionally use this parameter to force v2 capable device into translation mode to debug memory corruption that we suspect is caused by DMA writes.
To address the following comment from Joerg Roedel on the first version, v2 capability of device is completely ignored.
This breaks the iommu_v2 use-case, as it needs a direct mapping for the devices that support it.
And from Documentation/admin-guide/kernel-parameters.txt: This option does not override iommu=pt
Fixes: aafd8ba0ca74 ("iommu/amd: Implement add_device and remove_device")
Signed-off-by: Yu Zhao yuzhao@google.com Signed-off-by: Joerg Roedel jroedel@suse.de Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/iommu/amd_iommu.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c index 1167ff0416cf..325f3bad118b 100644 --- a/drivers/iommu/amd_iommu.c +++ b/drivers/iommu/amd_iommu.c @@ -438,7 +438,14 @@ static int iommu_init_device(struct device *dev)
dev_data->alias = get_alias(dev);
- if (dev_is_pci(dev) && pci_iommuv2_capable(to_pci_dev(dev))) { + /* + * By default we use passthrough mode for IOMMUv2 capable device. + * But if amd_iommu=force_isolation is set (e.g. to debug DMA to + * invalid address), we ignore the capability for the device so + * it'll be forced to go into translation mode. + */ + if ((iommu_pass_through || !amd_iommu_force_isolation) && + dev_is_pci(dev) && pci_iommuv2_capable(to_pci_dev(dev))) { struct amd_iommu *iommu;
iommu = amd_iommu_rlookup_table[dev_data->devid];