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Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api |
Date: |
Thu, 21 May 2009 20:33:08 +0300 |
User-agent: |
Mutt/1.5.18 (2008-05-17) |
On Thu, May 21, 2009 at 07:45:20PM +0300, Michael S. Tsirkin wrote:
> On Thu, May 21, 2009 at 02:31:26PM +0100, Paul Brook wrote:
> > On Thursday 21 May 2009, Paul Brook wrote:
> > > > > MSI provides multiple edge triggered interrupts, whereas traditional
> > > > > mode provides a single level triggered interrupt. My guess is most
> > > > > devices will want to treat these differently anyway.
> > > >
> > > > So, is qemu_send_msi better than qemu_set_irq.
> > >
> > > Neither. pci_send_msi, which is a trivial wrapper around stl_phys.
> >
> > To clarify, you seem to be trying to fuse two largely separate features
> > together.
> >
> > MSI is a standard PCI device capability[1] that involves the device
> > performing
> > a 32-bit memory write when something interesting occurs. These writes may
> > or
> > may not be directed at a APIC.
> >
> > The x86 APIC has a memory mapped interface that allows generation of CPU
> > interrupts in response response to memory writes. These may or may not come
> > from an MSI capable PCI device.
> >
> > Paul
> >
> > [1] Note a *device* capability, not a bus capability.
>
> Paul, so I went over specs, and what you say about APIC here does not
> seem to be what Intel actually implemented. Specifically, Intel
> implemented *MSI support in APIC*. This lets PCI devices, but not the CPU,
> signal interrupts by memory writes.
>
> For example, after reset, when CPU writes to address 0xfee00000 this
> is an access to a reserved register in APIC, but when PCI device
> does write to 0xfee00000, this triggers an interrupt to destination 0.
>
> See section 9.12 in Intel® 64 and IA-32 Architectures Software
> Developer’s Manual Volume 3A: System Programming Guide, Part 1
> http://www.intel.com/Assets/PDF/manual/253668.pdf
>
> So it seems that what we need to do in pci is:
>
> if (!msi_ops || msi_ops->send_msi(address, data))
> stl_phy(address, data);
>
> where send_msi is wired to apic_send_msi and
> where apic_send_msi returns an error for an address
> outside of the MSI range 0xfee00000 - 0xfeefffff
>
> Makes sense?
So I ended up with these ops:
allocate
free
update
send
which APIC will define and MSI emulation
will use. Here, send will return error for addresses
outside 0xfeexxxxx range, and device will do a plain
stl_phy.
--
MST
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, (continued)
- 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, 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 <=
- 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, 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, 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, Avi Kivity, 2009/05/21
- Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api, Michael S. Tsirkin, 2009/05/21