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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] KVM: arm64: Stop printing about MMIO accesses where
 ISV==0
Message-ID: <ZTjQ43gpJUvfh6rG@linux.dev>
References: <20231024210739.1729723-1-oliver.upton@linux.dev>
 <86il6v3z6d.wl-maz@kernel.org>
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On Wed, Oct 25, 2023 at 09:04:58AM +0100, Marc Zyngier wrote:

[...]

> While I totally agree that this *debug* statement should go, we should
> also replace it with something else.
> 
> Because when you're trying to debug a guest (or even KVM itself),
> seeing this message is a sure indication that the guest is performing
> an access outside of memory. The fact that KVM tries to handle it as
> MMIO is just an implementation artefact.
> 
> So I'd very much welcome a replacement tracepoint giving a bit more
> information, such as guest PC, IPA being accessed, load or store. With
> that, everybody wins.

Aren't we already covered by the kvm_guest_fault tracepoint? Userspace
can filter events on ESR to get the faults it cares about. I'm not
against adding another tracepoint, but in my experience kvm_guest_fault
has been rather useful for debugging any type of guest fault.

-- 
Thanks,
Oliver