Re: [PATCH 0/3] KVM: arm64: Load the stage-2 MMU from vcpu_load() for VHE

[Marc Zyngier <maz@kernel.org>]

On Fri, 06 Oct 2023 10:35:57 +0100,
Oliver Upton <oliver.upton@linux.dev> wrote:
> 
> Unlike nVHE, there is no need to switch the stage-2 MMU around on guest
> entry/exit in VHE mode as the host is running at EL2. Despite this KVM
> reloads the stage-2 on every guest entry, which is needless.
> 
> This series moves the setup of the stage-2 MMU context to vcpu_load()
> when running in VHE mode. This is likely to be a win across the board,
> but also allows us to remove an ISB on the guest entry path for systems
> with one of the speculative AT errata.
> 
> None of my machines affected by the AT errata are VHE-capable, so it'd
> be appreciated if someone could give this series a go and make sure I
> haven't wrecked anything.

It totally breaks on my A55 board. Running a single guest seems OK,
but running a number of the concurrently makes them explode early on
(faults in EFI...)

I guess we end-up running with the wrong VTTBR at times, which would
be interesting...

	M.

-- 
Without deviation from the norm, progress is not possible.