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xen-devel
Re: [Xen-devel] Re: [PATCH] xen: fix interrupt routing
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To: |
Avi Kivity <avi@xxxxxxxxxx> |
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Subject: |
Re: [Xen-devel] Re: [PATCH] xen: fix interrupt routing |
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From: |
Alexander Graf <agraf@xxxxxxx> |
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Date: |
Wed, 15 Jun 2011 18:54:30 +0200 |
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Cc: |
"xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>, Jan Kiszka <jan.kiszka@xxxxxxxxxxx>, "qemu-devel@xxxxxxxxxx" <qemu-devel@xxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>, Isaku Yamahata <yamahata@xxxxxxxxxxxxx>, Anthony Liguori <anthony@xxxxxxxxxxxxx> |
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Wed, 15 Jun 2011 09:56:20 -0700 |
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<alpine.DEB.2.00.1105261645560.12963@kaball-desktop> <21A10B78-49E2-453B-8AE6-48155E2071B5@xxxxxxx> <alpine.DEB.2.00.1105311123210.12963@kaball-desktop> <68B936C0-E230-4B48-A274-CB875ED92D5E@xxxxxxx> <1308053820.17937.72.camel@xxxxxxxxxxxxxxxxxxxxxx> <1D2C3E16-193F-4EEC-B7EF-AE038B4F2EE9@xxxxxxx> <alpine.DEB.2.00.1106141344260.12963@kaball-desktop> <4DF77E8E.40806@xxxxxxxxxxx> <alpine.DEB.2.00.1106141658180.12963@kaball-desktop> <DCAB4C78-3A84-41F0-8074-3E2712F60EE4@xxxxxxx> <4DF8DF11.1030206@xxxxxxxxxx> |
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Am 15.06.2011 um 18:34 schrieb Avi Kivity <avi@xxxxxxxxxx>:
> On 06/15/2011 11:24 AM, Alexander Graf wrote:
>> I'm actually not quite sure what exactly he's describing here. But if it's
>> bypassing the bus logic, it's not a normal PCI device :). Sure, there are
>> special case devices that also expose a PCI interface. But real PCI cards
>> that you plug in onto the PCI bus can't bypass the interrupt logic of the
>> bus, as the only interrupt wires they have go to the bus. And since the PCI
>> adapters we use in PC machines in Qemu are all non-special, guests can
>> possibly choke on this.
>>
>
> There actually is a special device in qemu - acpi power management is
> configured as a PCI device, but its interrupt is hard-wired to gsi 9 and is
> edge-triggered (so it can't share the irq line).
>
> I other devices that are special in this regard to also be part of the
> chipset, not devices you can plug into arbitrary slots.
Sure, platform devices can do that. Real PCI cards can not. Have you ever seen
an e1000 with direct mapped interrupt lines? :)
I admit though that we also emulate platform devices that happen to expose
themselves on the PCI bus. It's not common though and I wouldn't expect every
OS/driver to be happy about it.
Alex
>
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