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Re: [Qemu-devel] [PATCH 8/9] isa: refine irq reservations
From: |
Blue Swirl |
Subject: |
Re: [Qemu-devel] [PATCH 8/9] isa: refine irq reservations |
Date: |
Tue, 15 Sep 2009 22:08:16 +0300 |
On Tue, Sep 15, 2009 at 10:23 AM, Gerd Hoffmann <address@hidden> wrote:
> On 09/14/09 18:55, Blue Swirl wrote:
>>
>> On Mon, Sep 14, 2009 at 6:49 PM, Gerd Hoffmann<address@hidden> wrote:
>>>
>>> There are a few cases where IRQ sharing on the ISA bus is used and
>>> possible. In general only devices of the same kind can do that.
>>> A few use cases:
>>>
>>> * serial lines 1+3 share irq 4
>>> * serial lines 2+4 share irq 3
>>> * parallel ports share irq 7
>>> * ppc/prep: ide ports share irq 13
>>
>> There is another ppc/prep case where RTC and m48t59 share irq 8. The
>> attached patch converts m48t59 to ISA and makes this more visible.
>
> Hmm, ok. So scratch this and maybe use a 'sharing the irq is is fine with
> me' flag instead?
>
>> Does sharing of IRQs really have to be fatal? Wasn't ISA bus edge
>> triggered and so IRQ sharing was a bit unreliable (but not completely
>> broken) also on real HW?
>
> Well, the fundamental problem is that (1) the drivers must be prepared to
> handle that and (b) the hardware must be designed sanely. There are cases
> where it works fine (see the list above). It isn't true in general though.
> You can't configure two random devices (say sb16 + ne2k) to share the same
> irq and expect everything to work fine.
I wonder if the PREP machine is emulated correctly. I couldn't find
docs about PREP NVRAM or RTC.
- [Qemu-devel] [PATCH 0/9] ide: convert to qdev., Gerd Hoffmann, 2009/09/14
- [Qemu-devel] [PATCH 2/9] support media=cdrom for if=none, Gerd Hoffmann, 2009/09/14
- [Qemu-devel] [PATCH 1/9] qdev/pci: add pci_create_noinit(), Gerd Hoffmann, 2009/09/14
- [Qemu-devel] [PATCH 4/9] ide/qdev: add ide bus., Gerd Hoffmann, 2009/09/14
- [Qemu-devel] [PATCH 3/9] split away drive init from ide_init2(), Gerd Hoffmann, 2009/09/14
- [Qemu-devel] [PATCH 5/9] ide/pci: fix indention, Gerd Hoffmann, 2009/09/14
- [Qemu-devel] [PATCH 8/9] isa: refine irq reservations, Gerd Hoffmann, 2009/09/14
- [Qemu-devel] [PATCH 9/9] unbreak ppc/prep, Gerd Hoffmann, 2009/09/14
- [Qemu-devel] [PATCH 7/9] ide/isa: convert to qdev., Gerd Hoffmann, 2009/09/14
[Qemu-devel] [PATCH 6/9] ide/pci: convert to qdev., Gerd Hoffmann, 2009/09/14
Re: [Qemu-devel] [PATCH 0/9] ide: convert to qdev., Markus Armbruster, 2009/09/23