On Thu, Feb 20, 2025 at 12:45:46PM -0800, Nicolin Chen wrote:

This is documented as 'Transaction StreamID out of range.' so it would
by a hypervisor kernel bug to hit it

+ *       - 0x04 C_BAD_STE

I'm not sure we do enough validation to reject all bad STE fragments
so it makes sense this could happen.

+ *       - 0x06 F_STREAM_DISABLED

This looked guest triggerable to me.. so it makes sense

+ *       - 0x08 C_BAD_SUBSTREAMID
+ *       - 0x0a C_BAD_STE

Typo, this is C_BAD_CD

+ *       - 0x10 F_TRANSLATION
+ *       - 0x11 F_ADDR_SIZE
+ *       - 0x12 F_ACCESS
+ *       - 0x13 F_PERMISSION

List makes sense to me otherwise

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..

Jason