Hi,
On 9/24/19 4:25 AM, Raj, Ashok wrote:
Hi Jacob
On Mon, Sep 23, 2019 at 12:27:15PM -0700, Jacob Pan wrote:
In VT-d 3.0, scalable mode is introduced, which offers two level
translation page tables and nested translation mode. Regards to
GIOVA support, it can be simplified by 1) moving the GIOVA support
over 1st-level page table to store GIOVA->GPA mapping in vIOMMU,
2) binding vIOMMU 1st level page table to the pIOMMU, 3) using pIOMMU
second level for GPA->HPA translation, and 4) enable nested (a.k.a.
dual stage) translation in host. Compared with current shadow GIOVA
support, the new approach is more secure and software is simplified
as we only need to flush the pIOMMU IOTLB and possible device-IOTLB
when an IOVA mapping in vIOMMU is torn down.
.-----------.
| vIOMMU |
|-----------| .-----------.
| |IOTLB flush trap | QEMU |
.-----------. (unmap) |-----------|
| GVA->GPA |---------------->| |
'-----------' '-----------'
| | |
'-----------' |
<------------------------------
| VFIO/IOMMU
| cache invalidation and
| guest gpd bind interfaces
v
For vSVA, the guest PGD bind interface will mark the PASID as guest
PASID and will inject page request into the guest. In FL gIOVA case, I
guess we are assuming there is no page fault for GIOVA. I will need to
add a flag in the gpgd bind such that any PRS will be auto responded
with invalid.
Is there real need to enforce this? I'm not sure if there is any
limitation in the spec, and if so, can the guest check that instead?
For FL gIOVA case, gPASID is always 0. If a physical device is passed
through, hPASID is also 0; If an mdev device (representing an ADI)
instead, hPASID would be the PASID corresponding to the ADI. The
simulation software (i.e. QEMU) maintains a map between gPASID and
hPASID.
I second Ashok's idea. We don't need to distinguish these two cases in
the api and handle page request interrupt in guest as an unrecoverable
one.
Also i believe the idea is to overcommit PASID#0 such uses. Thought
we had a capability to expose this to the vIOMMU as well. Not sure if this
is already documented, if not should be up in the next rev.
Also, native use of IOVA FL map is not to be supported? i.e. IOMMU API
and DMA API for native usage will continue to be SL only?
.-----------.
| pIOMMU |
|-----------|
.-----------.
| GVA->GPA |<---First level
'-----------'
| GPA->HPA |<---Scond level
s/Scond/Second
Yes. Thanks!
Best regards,
Baolu
