Re: [Xen-devel] [PATCH 2/3] Refactor msi/msix restore code Part2

[Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>]

On 2013-07-24 21:46, Konrad Rzeszutek Wilk wrote:
> On Wed, Jul 24, 2013 at 11:08:10AM +0800, Zhenzhong Duan wrote:
> > xen_initdom_restore_msi_irqs trigger a hypercall to restore addr/data/mask
> > in dom0. It's better to do the same for default_restore_msi_irqs in baremetal.
> >
> > Move restore of mask in default_restore_msi_irqs, this could avoid mask
> > restored twice in dom0, once in hypercall, the other in kernel.
> Why not remove the hypercall then?
If removed, msi entry couldn't be restored, such as pci_reset_function 
who will reset pci registers.
> Or alter the function to detect
> whether the restore of the mask has occurred?
Then we need to add the check for dom0 only.
> > Without that, qlcnic driver calling pci_reset_function will lost interrupt
> > in dom0.
> >
> > Tested-by: Sucheta Chakraborty <sucheta.chakraborty@xxxxxxxxxx>
> > Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>
> > ---
> >   drivers/pci/msi.c |   17 ++++++++++++++---
> >   1 files changed, 14 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> > index 87223ae..922fb49 100644
> > --- a/drivers/pci/msi.c
> > +++ b/drivers/pci/msi.c
> > @@ -216,6 +216,8 @@ void unmask_msi_irq(struct irq_data *data)
> >   #ifdef HAVE_DEFAULT_MSI_RESTORE_IRQS
> >   void default_restore_msi_irqs(struct pci_dev *dev, int irq)
> >   {
> > +       int pos;
> > +       u16 control;
> >         struct msi_desc *entry;
> >   
> >   	entry = NULL;
> > @@ -228,8 +230,19 @@ void default_restore_msi_irqs(struct pci_dev *dev, int irq)
> >                 entry = irq_get_msi_desc(irq);
> >         }
> >   
> > -	if (entry)
> > +       if (entry) {
> >                 write_msi_msg(irq, &entry->msg);
> > +               if (dev->msix_enabled) {
> > +                       msix_mask_irq(entry, entry->masked);
> > +                       readl(entry->mask_base);
> > +               } else {
> > +                       pos = entry->msi_attrib.pos;
> > +                       pci_read_config_word(dev, pos + PCI_MSI_FLAGS,
> > +                                            &control);
> > +                       msi_mask_irq(entry, msi_capable_mask(control),
> > +                                    entry->masked);
> > +               }
> > +       }
> >   }
> >   #endif
> >   
> > @@ -406,7 +419,6 @@ static void __pci_restore_msi_state(struct pci_dev *dev)
> >         arch_restore_msi_irqs(dev, dev->irq);
> >   
> >   	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control);
> > -       msi_mask_irq(entry, msi_capable_mask(control), entry->masked);
> Before this patch we had:
>
>         write_msi_msg(..)
>         pci_read_config_work(PCI_MSI_FLAGS, &control)
>         pci_write_config_dword(~msi_capable_mask(control) | entry->masked)
>         control &= ~_PCI_MSI_FLAGS_QSIZE;
>         control |= ...
>         pci_write_config_dword(PCI_MSI_FLAGS, control)
>
> while with this you have now:
>
>         write_msi_msg(..)
>         pci_read_config_work(PCI_MSI_FLAGS, &_control)
>         pci_write_config_dword(~msi_capable_mask(_control) | entry->masked)
> -->  pci_read_config_work(PCI_MSI_FLAGS, &control)
>         control &= ~_PCI_MSI_FLAGS_QSIZE;
>         control |= ...
>         pci_write_config_dword(PCI_MSI_FLAGS, control)
>
> see the problem? The 'control' value in __pci_restore_msi_state reads the
> value _after_ it has been masked (which is now done in 
> default_restore_msi_irqs).
>
> Wouldn't that cause problems?
pci_write_config_dword(~msi_capable_mask(_control) | entry->masked) restore per 
vector
msi mask bits based on the support of PCI_MSI_FLAGS_MASKBIT. This is different 
from the
global mask bit in PCI_MSI_FLAGS.


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