On Tue, Oct 28, 2014 at 04:44:44PM +0000, David Vrabel wrote:
> On 27/10/14 19:45, Konrad Rzeszutek Wilk wrote:
> > On Mon, Oct 27, 2014 at 11:09:42AM +0000, David Vrabel wrote:
> >> On 27/10/14 02:44, Yijing Wang wrote:
> >>> Commit 0e4ccb1505a9 ("PCI: Add x86_msi.msi_mask_irq() and msix_mask_irq()")
> >>> fixed MSI mask bug which may cause kernel crash. But the commit
> >>> made MSI code complex. Introduce a new global flag "pci_msi_ignore_mask"
> >>> to ignore MSI/MSI-X to fix this issue, it's a cleaner solution.
> >>> And the commit 0e4ccb1505a9 will be reverted in the later patch.
> >>
> >> Reviewed-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> >>
> >> In the sense that it keeps the odd Xen behaviour. But...
> >>
> >> Konrad, why was this fixed like this in the first place? IMO, it would
> >
> > As 0e4ccb1505a9 explains:
> > PCI: Add x86_msi.msi_mask_irq() and msix_mask_irq()
> >
> > Certain platforms do not allow writes in the MSI-X BARs to setup or tear
> > down vector values. To combat against the generic code trying to write to
> > that and either silently being ignored or crashing due to the pagetables
> > being marked R/O this patch introduces a platform override.
> >
> > Note that we keep two separate, non-weak, functions default_mask_msi_irqs()
> > and default_mask_msix_irqs() for the behavior of the arch_mask_msi_irqs()
> > and arch_mask_msix_irqs(), as the default behavior is needed by x86 PCI
> > code.
> >
> > For Xen, which does not allow the guest to write to MSI-X tables - as the
> > hypervisor is solely responsible for setting the vector values - we
> > implement two nops.
>
> My question specifically was: could this be fixed by allowing writes to
> set/clear the mask bit? If so, why was this not done and could we do
No.
> this now?
>
> David
--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
