On 2017年02月20日 17:13, Liu, Yi L wrote:
-----Original Message-----
From: Jason Wang [mailto:[email protected]]
Sent: Monday, February 20, 2017 5:04 PM
To: Liu, Yi L <[email protected]>; Michael S. Tsirkin <[email protected]>; qemu-
[email protected]
Cc: Lan, Tianyu <[email protected]>; Peter Maydell
<[email protected]>; Tian, Kevin <[email protected]>; Eduardo
Habkost <[email protected]>; Peter Xu <[email protected]>; Alex
Williamson <[email protected]>; Paolo Bonzini
<[email protected]>; Richard Henderson <[email protected]>
Subject: Re: [Qemu-devel] [PULL 08/41] intel_iommu: support device iotlb
descriptor
On 2017年02月20日 16:27, Liu, Yi L wrote:
-----Original Message-----
From: Jason Wang [mailto:[email protected]]
Sent: Friday, February 17, 2017 2:43 PM
To: Liu, Yi L <[email protected]>; Michael S. Tsirkin
<[email protected]>; qemu- [email protected]
Cc: Peter Maydell <[email protected]>; Eduardo Habkost
<[email protected]>; Peter Xu <[email protected]>; Paolo Bonzini
<[email protected]>; Richard Henderson <[email protected]>; Tian,
Kevin <[email protected]>; Lan, Tianyu <[email protected]>;
Alex Williamson <[email protected]>
Subject: Re: [Qemu-devel] [PULL 08/41] intel_iommu: support device
iotlb descriptor
On 2017年02月17日 14:18, Liu, Yi L wrote:
-----Original Message-----
From: Jason Wang [mailto:[email protected]]
Sent: Thursday, February 16, 2017 1:44 PM
To: Liu, Yi L <[email protected]>; Michael S. Tsirkin
<[email protected]>; qemu- [email protected]
Cc: Peter Maydell <[email protected]>; Eduardo Habkost
<[email protected]>; Peter Xu <[email protected]>; Paolo Bonzini
<[email protected]>; Richard Henderson <[email protected]>; Tian,
Kevin <[email protected]>; Lan, Tianyu <[email protected]>;
Alex Williamson <[email protected]>
Subject: Re: [Qemu-devel] [PULL 08/41] intel_iommu: support device
iotlb descriptor
On 2017年02月16日 13:36, Liu, Yi L wrote:
-----Original Message-----
From: Qemu-devel
[mailto:[email protected]]
On Behalf Of Michael S. Tsirkin
Sent: Tuesday, January 10, 2017 1:40 PM
To: [email protected]
Cc: Peter Maydell <[email protected]>; Eduardo Habkost
<[email protected]>; Jason Wang <[email protected]>; Peter
Xu
<[email protected]>; Paolo Bonzini <[email protected]>; Richard
Henderson <[email protected]>
Subject: [Qemu-devel] [PULL 08/41] intel_iommu: support device
iotlb descriptor
From: Jason Wang <[email protected]>
This patch enables device IOTLB support for intel iommu. The
major work is to implement QI device IOTLB descriptor processing
and notify the device through iommu notifier.
Hi Jason/Michael,
Recently Peter Xu's patch also touched intel-iommu emulation. His
patch shadows second-level page table by capturing iotlb flush
from guest. It would result in page table updating in host. Does
this patch also use the same map/umap API provided by VFIO?
Yes, it depends on the iommu notifier too.
If it is, then I think it would also update page table in host. It
looks to be a duplicate update. Pls refer to the following
snapshot captured from section 6.5.2.5 of vtd spec.
"Since translation requests from a device may be serviced by
hardware from the IOTLB, software must always request IOTLB
invalidation
(iotlb_inv_dsc) before requesting corresponding Device-TLB
(dev_tlb_inv_dsc) invalidation."
Maybe for device-iotlb, we need a separate API which just pass
down the invalidate info without updating page table. Any thoughts?
cc Alex.
If we want ATS to be visible for guest (but I'm not sure if VFIO
support this), we probably need another notifier or a new flag.
Jason, for assigned device, I think guest could see ATS if the
assigned device supports ATS. I can see it when passthru iGPU.
Regards,
Yi L
Good to know this.
If I understand your suggestion correctly, you want a dedicated API
to flush a hardware device IOTLB. I'm not sure this is really needed.
yes, I'd like to have an extra API besides the current MAP/UNMAP.
I'm think whether or not we can do this without extra API or even don't need to
care about this.
There's some discussion of similar issue in the past (when ATS is
used for virtio- net/vhost), looks like we could solve this by not
trigger the UNMAP notifier unless it was device IOTLB inv desc if ATS
is enabled for the device? With this remote IOMMU/IOTLB can only get
invalidation request once. For VFIO, the under layer IOMMU can deal
with hardware device IOTLB without any extra efforts.
If I catch the background, I think it should be "not trigger the UNMAP
notifier when unless it was device IOTLB inv desc if ATS is enabled for the
device"
Seems not :)
I mean, if ATS is enabled for the device, only trigger UNMAP notifier when
processing device IOTLB. Then we can only have flush once. And host IOMMU
driver will take care of device IOTLB flush too.
hmmm, how about the iotlb inv desc which is prior to device-iotlb?
Any issue in this case?
I'm not sure
if it is practical to ignore the iotlb inv des since there is no SID info in it.
Yes, this needs some changes maybe.
Thanks
Regards,
Yi L
