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[Xen-devel] Re: [PATCH] xen: use the trigger info we already have to cho

To: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH] xen: use the trigger info we already have to choose the irq handler
From: Tom Goetz <tom.goetz@xxxxxxxxxxxxxxxxxxx>
Date: Wed, 25 May 2011 10:33:47 -0400
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
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On May 25, 2011, at 10:25 AM, Konrad Rzeszutek Wilk wrote:

> On Wed, May 25, 2011 at 12:33:23PM +0100, Stefano Stabellini wrote:
>> Do not use pirq_needs_eoi to decide which irq handler to use because Xen
>> always returns true if the guest does not support pirq_eoi_map.
>> Use the trigger information we already have from MP-tables and ACPI.
>> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
>> Reported-by: Thomas Goetz <tcgoetz@xxxxxxxxx>
>> Tested-by: Thomas Goetz <tcgoetz@xxxxxxxxx>
> Tom,
> Do you prefer those email addresses or tom.goetz@xxxxxxxxxxxxxxxxxxx ?

It doesn't matter to me. I'm signed up to Xen devel with the gmail address 
because I signed up before we had a domain for the company and never bothered 
to change it.

> ..
>> -    if (pirq_needs_eoi(irq))
>> +    if (shareable)
> Ok, so for dom0, the sharable flag is determined by the ACPI parsing.. good.
> And for MSI/MSI-X we use xen_bind_pirq_msi_to_irq which sets it to use 
> handle_edge_irq.
> The only hazard which you asked me on IRC is for PV guests with Xen PCI front.
> In those cases, we have no idea whether the "GSI" IRQ is edge or level and we
> just assume that anything under 16 is edge. Which is 99% right, except if you
> are to pass in the ACPI IRQ to the guest, or some other weird creature. The 
> part of the PCI front are OK too - they use the xen_bind_pirq_msi_to_irq call.
> So, putting on the todo list an extension to the PCI PV protocol to pass 
> information
> about the GSI's - whether they are edge or level.
> Patch is on the 2.6.40-rc1 train.

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