On 12/31/2010 05:05 AM, Sheng Yang wrote:
> > Existing code does not support PBA in assigned devices, so at least it's > not a regression there, and the virtio spec says nothing about this so > we should be fine. I agree. At least it's not a regression. And in fact we haven't seen any device driver use this. I've checked Linux kernel code, found no one used PCI_MSIX_PBA or msix_pba_offset_reg(). I guess it's fine to get MSI-X mask part in first, then deal with PBA part if necessary - though we haven't seen any driver use it so far. It won't be worse with this patch anyway...
In a way it is worse because before, the fix would belong in user space, which is easier to test and distribute. Now we have to fix it in the kernel.
However I recognize that drivers which rely on the pending bit are rare/nonexistent (likely on in preboot environments where interrupts are hard), so even if we do code it, it will likely be incorrect (certainly without a test).
So I'll accept the patch without PBA. Michael, what about supporting virtio? Can we base something on this patch?
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