From: Julien Grall <julien.grall@linaro.org>
To: Ian Campbell <Ian.Campbell@citrix.com>
Cc: xen-devel@lists.xenproject.org, tim@xen.org,
stefano.stabellini@citrix.com, patches@linaro.org
Subject: Re: [PATCH] xen/arm: IRQ: Protect IRQ to be shared between domains and XEN
Date: Wed, 15 Jan 2014 14:16:46 +0000 [thread overview]
Message-ID: <52D6984E.9070909@linaro.org> (raw)
In-Reply-To: <1389793244.3793.25.camel@kazak.uk.xensource.com>
On 01/15/2014 01:40 PM, Ian Campbell wrote:
> On Fri, 2014-01-10 at 20:50 +0000, Julien Grall wrote:
>> The current dt_route_irq_to_guest implementation set IRQ_GUEST no matter if the
>> IRQ is correctly setup.
>>
>> As IRQ can be shared between devices, if the devices are not assigned to the
>> same domain or Xen, this could result to IRQ route to the domain instead of
>> Xen ...
>>
>> Also avoid to rely on wrong behaviour when Xen is routing an IRQ to DOM0.
>>
>> Signed-off-by: Julien Grall <julien.grall@linaro.org>
>
> Does this patch relate to or rely on " setup_dt_irq: don't enable the
> IRQ if the creation has failed" at all?
There is no relation between the 2 patches. Each one fix a different bug.
>>
>> ---
>> Hopefully, none of the supported platforms have UARTs (the only device
>> currently used by Xen). It would be nice to have this patch for Xen 4.4 to
>> avoid waste of time for developer.
>
> Hrm, at some point I think we have to say no and I think post-rc "nice
> to avoid waste of time for developer" might be it. After all in a little
> over a month developers will be using 4.5-pre with this patch applied.
I'm fine to wait after Xen 4.4 release.
> What actually happens without this patch? The Xen console UART stops
> working because the IRQ is delivered to the guest and not to Xen?
Right.
> How did you discover this? Does this happen in practice on any of the
> platforms which Xen supports? I think in general shared interrupts are
> reasonably rare on ARM, especially for on-SoC peripherals which the UART
> very often will be.
By reading the code, IRQ_GUEST is set unconditionally in
dt_route_irq_to_guest.
All the current supported platform are safe.
---
Julien Grall
prev parent reply other threads:[~2014-01-15 14:16 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-10 20:50 [PATCH] xen/arm: IRQ: Protect IRQ to be shared between domains and XEN Julien Grall
2014-01-15 13:40 ` Ian Campbell
2014-01-15 14:16 ` Julien Grall [this message]
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