On Thu, Feb 20, 2025 at 07:24:07PM -0400, Jason Gunthorpe wrote:
On Thu, Feb 20, 2025 at 12:45:46PM -0800, Nicolin Chen wrote:
diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h index fd2f13a63f27..be9746ecdc65 100644 --- a/include/uapi/linux/iommufd.h +++ b/include/uapi/linux/iommufd.h @@ -1067,7 +1067,16 @@ enum iommu_veventq_type {
- struct iommu_vevent_arm_smmuv3 - ARM SMMUv3 Virtual Event
(IOMMU_VEVENTQ_TYPE_ARM_SMMUV3)- @evt: 256-bit ARM SMMUv3 Event record, little-endian.
(Refer to "7.3 Event records" in SMMUv3 HW Spec)
Reported event records: (Refer to "7.3 Event records" in SMMUv3 HW Spec)
- 0x02 C_BAD_STREAMIDThis is documented as 'Transaction StreamID out of range.' so it would by a hypervisor kernel bug to hit it
I see. Dropping it.
- 0x04 C_BAD_STEI'm not sure we do enough validation to reject all bad STE fragments so it makes sense this could happen.
- 0x06 F_STREAM_DISABLEDThis looked guest triggerable to me.. so it makes sense
Keeping these two.
- 0x08 C_BAD_SUBSTREAMID
- 0x0a C_BAD_STETypo, this is C_BAD_CD
Fixed.
But F_CD_FETCH and F_STE_FETCH seem to be complicated here, as both
F_STE_FETCH would indicate a hypervisor failure managing the stream table so no need to forward it.
report PA in their FetchAddr fields, although the spec does mention both might be injected to a guest VM:
- "Note: This event might be injected into a guest VM, as though from a virtual SMMU, when a hypervisor receives a stage 2 Translation-related fault indicating CD fetch as a cause (with CLASS == CD)."
That sounds like the VMM should be catching the F_TRANSLATION and convert it for the CLASS=CD
For F_CD_FETCH, at least the CD table pointer in the nested STE is an IPA, and all the entries in the CD table that can be 2-level are IPAs as well. So, we need some kinda reverse translation from a PA to IPA using its stage-2 mapping. I am not sure what's the best way to do that...
And if the F_TRANSLATION covers the case then maybe this just stays in the hypervisor?
Otherwise, perhaps not-supporting them in this series might be a safer bet?
Yeah, I would consider skipping F_CD_FETCH. May also just try it out and see what events come out on a CD fetch failure..
I will skip these two for now. Meanwhile, will try some hack to trigger a FETCH fault.
Thanks Nicolin