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Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api |
Date: |
Thu, 21 May 2009 13:01:50 +0100 |
User-agent: |
KMail/1.11.2 (Linux/2.6.29-2-amd64; KDE/4.2.2; x86_64; ; ) |
> >> The PCI bus doesn't need any special support (I think) but something on
> >> the other end needs to interpret those writes.
> >
> > Sure. But there's definitely nothing PCI specific about it. I assumed
> > this would all be contained within the APIC.
>
> MSIs are defined by PCI and their configuration is done using the PCI
> configuration space.
A MSI is just a regular memory write, and the PCI spec explicitly states that
a target (e.g. the APIC) is unable to distinguish between a MSI and any other
write. The PCI config bits just provide a way of telling the device where/what
to write.
> >> In any case we need some internal API for this, and qemu_irq looks like
> >> a good choice.
> >
> > What do you expect to be using this API?
>
> virtio, emulated devices capable of supporting MSI (e1000?), device
> assignment (not yet in qemu.git).
It probably makes sense to have common infrastructure in pci.c to
expose/implement device side MSI functionality. However I see no need for a
direct API between the device and the APIC. We already have an API for memory
accesses and MMIO regions. I'm pretty sure a system could implement MSI by
pointing the device at system ram, and having the CPU periodically poll that.
Paul
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, (continued)
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Michael S. Tsirkin, 2009/05/20
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Blue Swirl, 2009/05/20
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Michael S. Tsirkin, 2009/05/20
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Blue Swirl, 2009/05/20
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Michael S. Tsirkin, 2009/05/21
Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Paul Brook, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Avi Kivity, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Paul Brook, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Michael S. Tsirkin, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Avi Kivity, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api,
Paul Brook <=
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Avi Kivity, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Michael S. Tsirkin, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Paul Brook, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Avi Kivity, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Paul Brook, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Michael S. Tsirkin, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Paul Brook, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Paul Brook, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Michael S. Tsirkin, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Michael S. Tsirkin, 2009/05/21