On Tue, Jan 24, 2023 at 08:26:02AM -0800, Ricardo Koller wrote:
> On Mon, Jan 23, 2023 at 11:36:52PM +0000, Oliver Upton wrote:
> > On Tue, Jan 10, 2023 at 02:24:32AM +0000, Ricardo Koller wrote:
> > > Extend the read-only memslot tests in page_fault_test to test read-only PT
> > > (Page table) memslots. Note that this was not allowed before commit "KVM:
> > > arm64: Fix handling of S1PTW S2 fault on RO memslots" as all S1PTW faults
> > > were treated as writes which resulted in an (unrecoverable) exception
> > > inside the guest.
> >
> > Do we need an additional test that the guest gets nuked if TCR_EL1.HA =
> > 0b1 and AF is clear in one of the stage-1 PTEs?
> >
>
> That should be easy to add. The only issue is whether that's also a case
> of checking for very specific KVM behavior that could change in the
> future.
>From the perspective of the guest I believe this to match the
architecture. An external abort is appropriate if the hardware update to
a descriptor failed.
I believe that the current implementation of this in KVM is slightly
wrong, though. AFAICT, we encode the abort with an FSC of 0x10, which
indicates an SEA occurred outside of a table walk. The other nuance of
reporting SEAs due to a TTW is that the FSC encodes the level at which
the external abort occurred. Nonetheless, I think we can hide behind
R_BGPQR of DDI0487I.a and always encode a level of 0:
"""
If a synchronous External abort is generated due to a TLB or
intermediate TLB caching structure, including parity or ECC errors,
then all of the following are permitted:
- If the PE cannot precisely determine the translation stage at which
the error occurred, then it is reported and prioritized as a stage 1
fault.
- If the PE cannot precisely determine the lookup level at which the
error occurred, then the lookup level is reported and prioritized
as one of the following:
- The lowest-numbered lookup level that could have caused the error.
- If the PE cannot determine any information about the lookup level,
then level 0.
"""
Thoughts?
--
Thanks,
Oliver
