[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 1/2] pci: Add pci_device_get_host_irq
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH 1/2] pci: Add pci_device_get_host_irq |
Date: |
Fri, 1 Jun 2012 16:27:46 +0300 |
On Fri, Jun 01, 2012 at 02:52:56PM +0200, Jan Kiszka wrote:
> On 2012-05-30 22:31, Michael S. Tsirkin wrote:
> >>> So we'll just have PIIX_NUM_PIC_IRQS entries there and use
> >>> irq_count instead of the pic_levels bitmap.
> >>
> >> Just that this affects generic PCI code, not only PIIX-specific things.
> >
> > Yes but it's not a problem - pci_bus_irqs sets the map function and nirqs.
> >
> >> And that we need to save/restore some irq_count field according to the
> >> old semantics.
> >
> > Well, it's a bug: this is redundant info we should not have exposed it.
> >
> > Anyway, let's make the rest work properly and cleanly first, add a FIXME
> > for now, then we'll find a hack making it work for migration.
>
> It remains non-trivial: I got your patch working (a minor init issue),
> but yet without changing the number of IRQs for PIIX3, so keeping the
> irq_count semantics for this host bridge.
>
> Now I'm facing three possibilities of how to proceed:
They all look OK I think :) Some comments below.
> 1. Give up on the (currently broken) feature to write a vmstate for
> older QEMU versions.
>
> This will allow to declare the irq_count field in vmstate_pcibus
> unused, and we would have to restore it on vmload step-wise via the
> PCI devices. It would also allow to change its semantics for PIIX3,
> mapping directly to PIC IRQs.
I think that's okay too simply because these things are usually
easy to fix after the fact when the rest of the issues are addressed.
> 2. Keep writing a legacy irq_count field.
>
> This will require quite a few new APIs so that host bridges that
> want to change their nirq can still generate a compatible irq_count
> vmstate field. Namely:
> - A function to set up vmstate_irq_count and define a callback that
> the core will invoke to prepare the vmstate_irq_count before
> vmsave.
> - A function to obtain the IRQ mapping /without/ the final host
> bridge step. This is required so that the callback above can
> calculate the old state like in the PIIX3 case.
Does this really need to be so complex? It seems that we just need
pci_get_irq_count(bus, irq) which can use the existing map_irq API, no?
Then invoke that before save.
> 3. Keep irq_count and nirq as is, introduce additional map_host_irq.
>
> This is simpler than 2 and more compatible than 1. It would also
> allow to introduce the polarity and masking information more
> smoothly as we won't have to add it to existing map_irq callbacks
> then.
So what does it map, and to what?
Maybe we can make the name imply that somehow.
> Any other suggestions?
>
> Jan
> --
> Siemens AG, Corporate Technology, CT T DE IT 1
> Corporate Competence Center Embedded Linux
- Re: [Qemu-devel] [PATCH 1/2] pci: Add pci_device_get_host_irq, Jan Kiszka, 2012/06/01
- Re: [Qemu-devel] [PATCH 1/2] pci: Add pci_device_get_host_irq,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PATCH 1/2] pci: Add pci_device_get_host_irq, Jan Kiszka, 2012/06/01
- Re: [Qemu-devel] [PATCH 1/2] pci: Add pci_device_get_host_irq, Michael S. Tsirkin, 2012/06/01
- Re: [Qemu-devel] [PATCH 1/2] pci: Add pci_device_get_host_irq, Jan Kiszka, 2012/06/01
- Re: [Qemu-devel] [PATCH 1/2] pci: Add pci_device_get_host_irq, Michael S. Tsirkin, 2012/06/01
- Re: [Qemu-devel] [PATCH 1/2] pci: Add pci_device_get_host_irq, Jan Kiszka, 2012/06/01
- Re: [Qemu-devel] [PATCH 1/2] pci: Add pci_device_get_host_irq, Michael S. Tsirkin, 2012/06/01
- Re: [Qemu-devel] [PATCH 1/2] pci: Add pci_device_get_host_irq, Jan Kiszka, 2012/06/01
- Re: [Qemu-devel] [PATCH 1/2] pci: Add pci_device_get_host_irq, Michael S. Tsirkin, 2012/06/01
- Re: [Qemu-devel] [PATCH 1/2] pci: Add pci_device_get_host_irq, Jan Kiszka, 2012/06/01
- Re: [Qemu-devel] [PATCH 1/2] pci: Add pci_device_get_host_irq, Michael S. Tsirkin, 2012/06/01