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From:   Oliver Upton <oliver.upton@linux.dev>
To:     Marc Zyngier <maz@kernel.org>
Cc:     kvmarm@lists.linux.dev, kvm@vger.kernel.org,
        James Morse <james.morse@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Zenghui Yu <yuzenghui@huawei.com>
Subject: Re: [PATCH 0/3] KVM: arm64: Load the stage-2 MMU from vcpu_load()
 for VHE
Message-ID: <ZSBN0nAKANRHsxll@linux.dev>
References: <20231006093600.1250986-1-oliver.upton@linux.dev>
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Hey Marc,

On Fri, Oct 06, 2023 at 04:03:32PM +0100, Marc Zyngier wrote:
> On Fri, 06 Oct 2023 14:33:04 +0100,
> Marc Zyngier <maz@kernel.org> wrote:
> 
> Still talking to myself! :D

Seems like you had a good bit of fun :)

> >
> > However, this isn't enough.
> > 
> > [   63.450113] Oh crap 400000435c001 vs 3000004430001
> > 
> > So there are situations where we end-up with the wrong VTTBR, rather
> > than the wrong VMID, which is even worse. Haven't worked out the
> > scenario yet, but it apparently involves being preempted by a vcpu
> > from a different VM and not doing the right thing.
> 
> Actually, no. It is the MMU notifiers kicking in and performing TLB
> invalidation for a guest while we're in the context of another. The
> joy of running 4 large VMs on a box with 2GB of RAM, basically running
> from swap.

Whelp, looks like my self-rule of no patches on the list after midnight
is in force again. Clearly this was all quite gently tested, thanks for
being the guinea pig.

> There's the sum of my hacks, which keeps the box alive.

Thanks! I'll roll it into v2 so we have something that actually works.

-- 
Thanks,
Oliver