Messages in this thread | | | Date | Mon, 20 Mar 2023 14:22:42 -0700 | From | Nicolin Chen <> | Subject | Re: [PATCH v1 14/14] iommu/arm-smmu-v3: Add arm_smmu_cache_invalidate_user |
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On Mon, Mar 20, 2023 at 03:45:54PM -0300, Jason Gunthorpe wrote: > On Mon, Mar 20, 2023 at 09:59:45AM -0700, Nicolin Chen wrote: > > On Mon, Mar 20, 2023 at 01:04:35PM -0300, Jason Gunthorpe wrote: > > > > > > > We need an ioctl for this, I think. To load a map of vSID to dev_id > > > > > into the driver. Kernel will convert dev_id to pSID. Driver will > > > > > program the map into HW. > > > > > > > > Can we just pass a vSID via the alloc ioctl like this? > > > > > > > > ----------------------------------------------------------- > > > > @@ -429,7 +429,7 @@ struct iommu_hwpt_arm_smmuv3 { > > > > #define IOMMU_SMMUV3_FLAG_VMID (1 << 1) /* vmid override */ > > > > __u64 flags; > > > > __u32 s2vmid; > > > > - __u32 __reserved; > > > > + __u32 sid; > > > > __u64 s1ctxptr; > > > > __u64 s1cdmax; > > > > __u64 s1fmt; > > > > ----------------------------------------------------------- > > > > > > > > An alloc is initiated by an SMMU_CMD_CFGI_STE command that has > > > > an SID filed anyway. > > > > > > No, a HWPT is not a device or a SID. a HWPT is an ASID in the ARM > > > model. > > > > > > dev_id is the SID. > > > > > > The cfgi_ste will carry the vSID which is mapped to a iommufd dev_id. > > > > > > The kernel has to translate the vSID to the dev_id to the pSID to > > > issue an ATC invalidation for the correct entity. > > > > OK. This narrative makes sense. I think our solution (the entire > > stack) here mixes these two terms between HWPT/ASID and STE/SID. > > HWPT is an "ASID/DID" on Intel and a CD table on SMMUv3 > > > What QEMU does is trapping an SMMU_CMD_CFGI_STE command to send > > the host an HWPT alloc ioctl. The former one is based on an SID > > or a device, while the latter one is based on ASID. > > > > So the correct way should be for QEMU to maintain an ASID-based > > list, corresponding to the s1ctxptr from STEs, and only send an > > alloc ioctl upon a new s1ctxptr/ASID. Meanwhile, at every trap > > of SMMU_CMD_CFGI_STE, it calls a separate ioctl to tie a vSID to > > a dev_id (and pSID accordingly). > > It is not ASID, it just s1ctxptr's - de-duplicate them.
SMMU has "ASID" too. And it's one per CD table. It can be also seen as one per iommu_domain.
The following are lines from arm_smmu_domain_finalise_s1(): ... ret = xa_alloc(&arm_smmu_asid_xa, &asid, &cfg->cd, XA_LIMIT(1, (1 << smmu->asid_bits) - 1), GFP_KERNEL); ... cfg->cd.asid = (u16)asid; ...
> Do something about SMMUv3 not being able to interwork iommu_domains > across instances
I don't follow this one. Device instances?
> > In another word, an SMMU_CMD_CFGI_STE should do a mandatory SID > > ioctl and an optional HWPT alloc ioctl (only allocates a HWPT if > > the s1ctxptr in the STE is new). > > No, there is no SID ioctl at the STE stage. > > The vSID was decided by qemu before the VM booted. It created it when > it built the vRID and the vPCI device. The vSID is tied to the vfio > device FD. > > Somehow the VM knows the relationship between vSID and vPCI/vRID. IIRC > this is passed in through ACPI from qemu.
Yes.
> So vSID is an alais for the dev_id in iommfd language, and quemu > always has a translation table for it.
I see.
> So CFGI_STE maps to allocating a de-duplicated HWPT for the CD table, > and then a replace operation on the device FD represented by the vSID > to change the pSTE to point to the HWPT. > > The HWPT is effectively the "shadow STE".
IIUIC, the ioctl for the link of vSID/dev_id should happen at the stage when boot boots, while the HWPT alloc ioctl happens at CFGI_STE.
> > What could be a good prototype of the ioctl? Would it be a VFIO > > device one or IOMMUFD one? > > If we load the vSID table it should be a iommufd one, linked to the > ARM SMMUv3 driver and probably take in a pointer to an array of > vSID/dev_id pairs. Maybe an add/remove type of operation.
Will try some solution.
> > > I would expect that if invalidation can fail that we have a way to > > > signal that failure back to the guest. > > > > That's plausible to me, and it could apply to a translation > > fault too. So, should we add back the iommufd infrastructure > > for the fault injection (without PRI), in v2? > > It would be nice if things were not so big, I don't think we need to > tackle translation fault at this time, but we should be thinking about > what invalidation cmd fault converts into.
Will see if we can add a compact one, or some other solution for invalidation fault only.
Thanks Nic
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