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Re: [Xen-devel]Question about qemu interrupt deliver.

To: "Xu, Anthony" <anthony.xu@xxxxxxxxx>, Keir Fraser <keir@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel]Question about qemu interrupt deliver.
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Thu, 30 Nov 2006 09:15:09 +0000
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Thread-topic: [Xen-devel]Question about qemu interrupt deliver.
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1a. If there is opportunity for code reuse we should aim for it. I'd be
happy to see a root hvm/ directory. Clearly the IOAPIC code is already
shared and that could be made more explicit by moving the source file.

1b. I don't care about the hypervisor getting bigger if the alternative is
simply pushing code into other critical components. If the device models are
buggy then HVM domains do not work -- it doesn't matter whether the code is
in Xen or in qemu-dm. In some respects I prefer the former as I will tend to
audit Xen code more aggressively. There is a downside that the effects of
bad code may not be limited to a single guest but we should be aiming for
high-quality code regardless of the context in which it executes.

2. I browsed a few drivers and concluded that most have correct INTx
assertion behaviour. Any that don't should be fixed. Hacks like the 0-1
pulse done for periodic timers need addressing in a future patch, for
example.

 -- Keir

On 30/11/06 02:52, "Xu, Anthony" <anthony.xu@xxxxxxxxx> wrote:

> 1.  PCI->link and PCI->GSI are put into hypervisor. But it is under x86
> directory,
>      it's not convenient for other architecture to share these information.
> 
>      Seems there is a trend, we move code from other component into
> hypersivor,
>      is there any criteria whether we should move code into hypersivor?
> Otherwise 
>     hypersivor  will become bigger and bigger quickly, that's not definitely
> what we want.
> 
> 2.  hypervisor uses hvm_irq->gsi_assert_count[gsi] to emulate level triggered
> interrupt.
>     The code itself is correct, but it sets a high stardant for PCI device
> emulator, it PCI device
>      emulator set irq_line low/hight twice continuously, that will lead to
> interrupt lost or spurios
>      interrupt.


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