On Wed, 2007-03-28 at 00:39 -0600, Eric W. Biederman wrote: > Michael Ellerman <[EMAIL PROTECTED]> writes: > > > It's an arch detail whether MSI irqs need to be masked using the PCI > > MSI registers. > > Agreed. It isn't an arch detail that they need to be unmasked in > the pci configuration space. > > I assume this patch is motivated just to make arch support easier > and not for RTAS compatibility reason. > > > This changes behaviour in that previously we unconditionally masked > > all MSIs, eventhough we only ever enable one, whereas now we only > > mask the irqs we're using. > > > > To be super paranoid I have the archs mask the irq before they write > > the msi message, just in case the device doesn't respect the MSI enable > > bit or MSI is already enabled or something else crazy. > > > > For MSI-X this might mean we mask the already masked MSI-X on the device, > > but that should be harmless. > > I don't think this patch really makes sense. I think we should mask > all possible vectors for msi and msi-x initially in the generic code > and then unmask them. > > If we were trying to support Dave Miller's example of hypervisors > that don't let us touch the msi registers I think there would be a > point. As it is I think this just makes the code more brittle.
The main motivation was to have the arch in control of as much direct register writing as possible. Even though our HV does allow us to write to config space, it's not obviously safe for Linux to be flipping bits and also calling the HV to configure things. What's worse, I don't have hardware that supports the mask bits, so I can't test it. I also thought this would save me from having custom MSI irq_chips for the powerpc backends. But I think I need them now anyway, so I guess that's not a concern. So I guess we'll drop this one, although I might try and tidy up the implementation of "mask all MSIs" in msi_capability_init() as another patch. cheers -- Michael Ellerman OzLabs, IBM Australia Development Lab wwweb: http://michael.ellerman.id.au phone: +61 2 6212 1183 (tie line 70 21183) We do not inherit the earth from our ancestors, we borrow it from our children. - S.M.A.R.T Person
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