Messages in this thread | | | Subject | Re: [RFC PATCH 0/4] Use 1st-level for DMA remapping in guest | From | Lu Baolu <> | Date | Tue, 24 Sep 2019 12:40:29 +0800 |
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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
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