[PATCH v2 0/4] KVM: arm64: Hide unsupported MPAM from the guest

[Oliver Upton]

On Fri, Jan 19, 2024 at 05:15:59PM +0000, James Morse wrote:

[...]

> > We've already done something similar to hide our mistakes with IMP DEF
> > PMU versions in commit f90f9360c3d7 ("KVM: arm64: Rewrite IMPDEF PMU
> > version as NI"), and I think MPAM may be a good candidate for something
> > similar.
> 
> As there is precedent, I feel less dirty doing that!
> 
> This also solves the problem of the VMM re-writing the broken value after the vCPU has
> started running, and getting a surprise error. A weird side effect of doing this would be
> you can write MPAM=1 on A53 and KVM will ignore it, I don't want user-space to start
> relying on that! I'll add a final-cap check so this can only be ignored on hardware that
> actually has MPAM, and could have been exposed to the bug.

Ah, good idea. I probably should've done something similar in the PMU
case.

-- 
Thanks,
Oliver