From: Pavel Fedin <p.fedin@samsung.com>
To: 'Marc Zyngier' <marc.zyngier@arm.com>
Cc: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
"'Christoffer Dall'" <christoffer.dall@linaro.org>,
"'Alex Bennée'" <alex.bennee@linaro.org>
Subject: RE: [PATCH] KVM: arm/arm64: BUG: Fix losing level-sensitive interrupts
Date: Wed, 26 Aug 2015 14:33:06 +0300 [thread overview]
Message-ID: <00d901d0dff2$fa5616d0$ef024470$@samsung.com> (raw)
In-Reply-To: <55DD9F5B.4080602@arm.com>
Hello!
> As for v4.1 not having that problem, the pl011 driver has gone though a
> lot if rework lately, and I wouldn't be surprised if it now exhibited a
> different behaviour thanks to the broken userspace behaviour.
Sorry, you misunderstood me. Or i wrote badly. I meant that _KVM_ did not have this particular
problem in kernel v4.0, because:
http://lxr.free-electrons.com/source/virt/kvm/arm/vgic.c?v=4.0#L998
you see, LR_STATE_PENDING is assigned unconditionally. Is this code correct? I believe yes. Compare
with:
http://lxr.free-electrons.com/source/virt/kvm/arm/vgic.c#L1104
Now it is possible to have neither PENDING nor ACTIVE irq. Does it even make sense? So what is
wrong with the modification as follows?
--- cut ---
if (vgic_irq_is_active(vcpu, irq)) {
vlr.state |= LR_STATE_ACTIVE;
kvm_debug("Set active, clear distributor: 0x%x\n", vlr.state);
vgic_irq_clear_active(vcpu, irq);
vgic_update_state(vcpu->kvm);
} else {
vlr.state |= LR_STATE_PENDING;
kvm_debug("Set pending: 0x%x\n", vlr.state);
}
--- cut ---
Alex, are you reading us? Can you explain, why you introduced that extra check?
> And what you're suggesting is to actually introduce a bug.
Why would that be a bug, if it was not a bug in kernel 4.0?
Kind regards,
Pavel Fedin
Expert Engineer
Samsung Electronics Research center Russia
next prev parent reply other threads:[~2015-08-26 11:33 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-26 6:46 [PATCH] KVM: arm/arm64: BUG: Fix losing level-sensitive interrupts Pavel Fedin
2015-08-26 8:27 ` Marc Zyngier
2015-08-26 10:58 ` Pavel Fedin
2015-08-26 11:13 ` Marc Zyngier
2015-08-26 11:33 ` Pavel Fedin [this message]
2015-08-26 13:11 ` Pavel Fedin
2015-08-26 14:03 ` Christoffer Dall
2015-08-26 14:02 ` Christoffer Dall
2015-08-26 14:26 ` Pavel Fedin
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