Messages in this thread |  | | | Date | Wed, 23 Jun 2010 08:51:53 -0700 | | From | Jesse Barnes <> | | Subject | Re: [PATCH for-2.6.35] virtio-pci: disable msi at startup |
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On Wed, 23 Jun 2010 18:35:55 +0300 Avi Kivity <avi@redhat.com> wrote:
> On 06/23/2010 06:26 PM, Michael S. Tsirkin wrote: > > > > > >>> > >>> > >>>>>> Shouldn't a reset be equivalent to power cycling? > >>>>>> > >>>>>> > >>>>>> > >>>>> If we did this, driver would need to restore registers > >>>>> such as BAR etc. > >>>>> > >>>>> > >>>>> > >>>> We could save/restore the registers we care about. > >>>> > >>>> > >>> It seems easier to clear registers we care about. > >>> > >> We know the registers we care about, we don't know the ones we don't. > >> > > If/when we use more registers, we can update driver to clear them on start. > > > > The kdump kernel may not load drivers for those extra devices.
FLR or another type of reset also has the nice property of bringing the device into a known state. kexec/kdump has always been vulnerable to having devices in partial states when the new kernel loads; would be good to make it more robust.
> > >> I'm talking about FLRing all cards, not just those you want to use. > >> > > reset using FLR/PM is complex because of the need to save/restore > > config space. Doing this on a crashing kernel sounds scary. > > > > Well, you only need to save/restore for the devices you use. The rest > you reset and forget. > > I don't really see why copying some config space is crazy.
We could push any needed save/restore of core settings and regs into the PCI core like we do for PM. That would save a bunch of driver trouble...
-- Jesse Barnes, Intel Open Source Technology Center
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