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Re: [Qemu-devel] [PATCH] Register usb-uhci reset function.
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [PATCH] Register usb-uhci reset function. |
Date: |
Tue, 16 Jun 2009 19:41:05 +0100 |
User-agent: |
KMail/1.11.4 (Linux/2.6.29-2-amd64; KDE/4.2.4; x86_64; ; ) |
>> If allow devices to be reset independently then they should probably set
>> theit IRQ output on reset.
>
>It is not "if" it is "when". We have to allow device to be reset
> independently for hot-unplug.
I'm not entirely convinced about reset-on-hotunplug. What about a device that
pulls its IRQ line high on reset?
> > The only relevant circumstances are if the devices raises an IRQ, and is
> > then reset by software while the system is running. It's got nothing to
> > do with piix3, PCI bus interrupt sharing or system reset. If you are
> > seeing problems after a system reset then your bug lies elsewhere.
>
> So you apparently never heard about hardware reset? You never saw buggy
> guests that does not reset HW before reboot?
Clearing device state on full system reset makes sense because the whole point
is that we're returning the system to its power-on state.
Lowering the IRQ when a single device is reset also makes sense.
However having the device explicit set its IRQ line during a full system reset
is a different matter. This is probably harmless most of the time, and may
paper over other bugs (e.g. the PCI bus not being reset properly). However I
do not believe it is the correct justification for these changes.
Paul
Re: [Qemu-devel] [PATCH] Register usb-uhci reset function., Blue Swirl, 2009/06/16
Re: [Qemu-devel] [PATCH] Register usb-uhci reset function., Anthony Liguori, 2009/06/16
Re: [Qemu-devel] [PATCH] Register usb-uhci reset function., Filip Navara, 2009/06/17