Re: [Xen-devel] [PVH]: Help: msi.c

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 14 Dec 2012, Mukesh Rathor wrote:
> On Thu, 13 Dec 2012 14:25:16 +0000
> Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> 
> > On Thu, 13 Dec 2012, Jan Beulich wrote:
> > > >>> On 13.12.12 at 13:19, Stefano Stabellini
> > > >>> <stefano.stabellini@xxxxxxxxxxxxx>
> > > wrote:
> > > > On Thu, 13 Dec 2012, Jan Beulich wrote:
> > > >> >>> On 13.12.12 at 02:43, Mukesh Rathor
> > > >> >>> <mukesh.rathor@xxxxxxxxxx> wrote:
> > 
> > Actually I think that you might be right: just looking at the code it
> > seems that the mask bits get written to the table once as part of the
> > initialization process:
> > 
> > pci_enable_msix -> msix_capability_init -> msix_program_entries
> > 
> > Unfortunately msix_program_entries is called few lines after
> > arch_setup_msi_irqs, where we call PHYSDEVOP_map_pirq to map the MSI
> > as a pirq.
> > However after that is done, all the masking/unmask is done via
> > irq_mask that we handle properly masking/unmasking the corresponding
> > event channels.
> > 
> > 
> > Possible solutions on top of my head:
> > 
> > - in msix_program_entries instead of writing to the table directly
> > (__msix_mask_irq), call desc->irq_data.chip->irq_mask(); 
> > 
> > - replace msix_program_entries with arch_msix_program_entries, but it
> > would probably be unpopular.
> 
> 
> Can you or Jan or somebody please take that over? I can focus on other
> PVH things then and try to get a patch in asap.

The following patch moves the MSI-X masking before arch_setup_msi_irqs,
that is when Linux calls PHYSDEVOP_map_pirq that is the hypercall that
causes Xen to execute msix_capability_init.

I don't have access to a machine with an MSI-X device right now so I
have only tested the appended patch with MSI.

---



diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index a825d78..ef73e80 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -652,11 +652,22 @@ static void msix_program_entries(struct pci_dev *dev,
        int i = 0;
 
        list_for_each_entry(entry, &dev->msi_list, list) {
+               entries[i].vector = entry->irq;
+               irq_set_msi_desc(entry->irq, entry);
+               i++;
+       }
+}
+
+static void msix_mask_entries(struct pci_dev *dev,
+                                       struct msix_entry *entries)
+{
+       struct msi_desc *entry;
+       int i = 0;
+
+       list_for_each_entry(entry, &dev->msi_list, list) {
                int offset = entries[i].entry * PCI_MSIX_ENTRY_SIZE +
                                                PCI_MSIX_ENTRY_VECTOR_CTRL;
 
-               entries[i].vector = entry->irq;
-               irq_set_msi_desc(entry->irq, entry);
                entry->masked = readl(entry->mask_base + offset);
                msix_mask_irq(entry, 1);
                i++;
@@ -696,6 +707,8 @@ static int msix_capability_init(struct pci_dev *dev,
        if (ret)
                return ret;
 
+       msix_mask_entries(dev, entries);
+
        ret = arch_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSIX);
        if (ret)
                goto error;

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