Re: [PATCH] KVM: arm64: Disable preemption in kvm_arch_hardware_enable()

[Marc Zyngier <maz@kernel.org>]

On Tue, 04 Jul 2023 19:32:09 +0100,
Kristina Martsenko <kristina.martsenko@arm.com> wrote:
> 
> On 03/07/2023 17:35, Marc Zyngier wrote:
> > Since 0bf50497f03b ("KVM: Drop kvm_count_lock and instead protect
> > kvm_usage_count with kvm_lock"), hotplugging back a CPU whilst
> > a guest is running results in a number of ugly splats as most
> > of this code expects to run with preemption disabled, which isn't
> > the case anymore.
> > 
> > While the context is preemptable, it isn't migratable, which should
> > be enough. But we have plenty of preemptible() checks all over
> > the place, and our per-CPU accessors also disable preemption.
> > 
> > Since this affects released versions, let's do the easy fix first,
> > disabling preemption in kvm_arch_hardware_enable(). We can always
> > revisit this with a more invasive fix in the future.
> > 
> > Fixes: 0bf50497f03b ("KVM: Drop kvm_count_lock and instead protect kvm_usage_count with kvm_lock")
> > Reported-by: Kristina Martsenko <kristina.martsenko@arm.com>
> > Tested-by: Kristina Martsenko <kristina.martsenko@arm.com>
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > Link: https://lore.kernel.org/r/aeab7562-2d39-e78e-93b1-4711f8cc3fa5@arm.com
> > Cc: stable@vger.kernek.org # v6.3, v6.4
> 
> Typo here, didn't make it to the stable list (kernek.org -> kernel.org)

Yeah, I had a bad day (I also typoed Catalin's address in a separate
email...).

	M.

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