Re: [PATCH 0/5] KVM: arm/arm64: fix some races and allow userspace to set MPIDR

[Christoffer Dall <christoffer.dall@linaro.org>]

Hi Drew,

On Mon, Feb 27, 2017 at 06:54:59PM +0100, Andrew Jones wrote:
> This series fixes four races. Two are easy to produce with a
> kvm-unit-test test[1], but the other two would be quite hard. I
> didn't even try to produce those. The two hard to produce races are
> addressed by changing vcpu->arch.pause and vcpu->arch.power_off to
> vcpu requests. The two easy to produce races are addressed in two
> different ways: the first takes advantage of power_off having been
> changed to a vcpu request, the second caches vcpu MPIDRs in order
> to avoid extracting them from sys_regs. When introducing the MPIDR
> cache we also introduce a new feature (userspace settable MPIDRs).
> 
> Support for userspace settable MPIDRs was already posted once[2],
> but rejected due to not having a use case. We have one now, which
> is to satisfy QEMU's need for the MPDIR information very early,
> before vcpu-init has even run. While the original posting author
> wasn't me, I've taken authorship now, as I've changed the patch
> substantially. If anybody disagrees with that, then feel free to
> suggest alternatives. The QEMU counterpart has been posted[3].
> 
> This series is based on Radim's recent posting[4] that improves
> the vcpu-request framework. I've tested the series on a couple
> AArch64 platforms and compile-tested the arm bits.

So as we discussed during lunch today, it would be awesome if you could
split this up into a series that fixes the identified races and a
separate series for the introduction of supporting setting the MPIDR
from user space.

Thanks a lot!
-Christoffer