On 17/02/2020 1:01 pm, Michael S. Tsirkin wrote:
On Mon, Feb 17, 2020 at 10:01:07AM +0100, Jean-Philippe Brucker wrote:
On Sun, Feb 16, 2020 at 04:50:33AM -0500, Michael S. Tsirkin wrote:
On Fri, Feb 14, 2020 at 04:57:11PM +0000, Robin Murphy wrote:
On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote:
With the built-in topology description in place, x86 platforms can now
use the virtio-iommu.
Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
---
drivers/iommu/Kconfig | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 068d4e0e3541..adcbda44d473 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -508,8 +508,9 @@ config HYPERV_IOMMU
config VIRTIO_IOMMU
bool "Virtio IOMMU driver"
depends on VIRTIO=y
- depends on ARM64
+ depends on (ARM64 || X86)
select IOMMU_API
+ select IOMMU_DMA
Can that have an "if X86" for clarity? AIUI it's not necessary for
virtio-iommu itself (and really shouldn't be), but is merely to satisfy the
x86 arch code's expectation that IOMMU drivers bring their own DMA ops,
right?
Robin.
In fact does not this work on any platform now?
There is ongoing work to use the generic IOMMU_DMA ops on X86. AMD IOMMU
has been converted recently [1] but VT-d still implements its own DMA ops
(conversion patches are on the list [2]). On Arm the arch Kconfig selects
IOMMU_DMA, and I assume we'll have the same on X86 once Tom's work is
complete. Until then I can add a "if X86" here for clarity.
Thanks,
Jean
[1] https://lore.kernel.org/linux-iommu/20190613223901.9523-1-murphyt7@xxxxxx/
[2] https://lore.kernel.org/linux-iommu/20191221150402.13868-1-murphyt7@xxxxxx/
What about others? E.g. PPC?
That was the point I was getting at - while iommu-dma should build just
fine for the likes of PPC, s390, 32-bit Arm, etc., they have no
architecture code to correctly wire up iommu_dma_ops to devices. Thus
there's currently no point pulling it in and pretending it's anything
more than a waste of space for architectures other than arm64 and x86.
It's merely a historical artefact of the x86 DMA API implementation that
when the IOMMU drivers were split out to form drivers/iommu they took
some of their relevant arch code with them.
Robin.
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