genirq/msi: Make sure PCI MSIs are activated early

Bharat Kumar Gogada reported issues with the generic MSI code, where the
end-point ended up with garbage in its MSI configuration (both for the vector
and the message).

It turns out that the two MSI paths in the kernel are doing slightly different
things:

generic MSI: disable MSI -> allocate MSI -> enable MSI -> setup EP
PCI MSI: disable MSI -> allocate MSI -> setup EP -> enable MSI

And it turns out that end-points are allowed to latch the content of the MSI
configuration registers as soon as MSIs are enabled.  In Bharat's case, the
end-point ends up using whatever was there already, which is not what you
want.

In order to make things converge, we introduce a new MSI domain flag
(MSI_FLAG_ACTIVATE_EARLY) that is unconditionally set for PCI/MSI. When set,
this flag forces the programming of the end-point as soon as the MSIs are
allocated.

A consequence of this is that we have an extra activate in irq_startup, but
that should be without much consequence.

tglx:

 - Several people reported a VMWare regression with PCI/MSI-X passthrough. It
   turns out that the patch also cures that issue.

 - We need to have a look at the MSI disable interrupt path, where we write
   the msg to all zeros without disabling MSI in the PCI device. Is that
   correct?

Fixes: 52f518a3a7c2 "x86/MSI: Use hierarchical irqdomains to manage MSI interrupts"
Reported-and-tested-by: Bharat Kumar Gogada <bharat.kumar.gogada@xilinx.com>
Reported-and-tested-by: Foster Snowhill <forst@forstwoof.ru>
Reported-by: Matthias Prager <linux@matthiasprager.de>
Reported-by: Jason Taylor <jason.taylor@simplivity.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1468426713-31431-1-git-send-email-marc.zyngier@arm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index a02981efdad570148e39925cfbe4a8579ca7f7ca..eafa6138a6b81866a3bc09739ab3398513746253 100644 (file)
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1411,6 +1411,8 @@ struct irq_domain *pci_msi_create_irq_domain(struct fwnode_handle *fwnode,
        if (info->flags & MSI_FLAG_USE_DEF_CHIP_OPS)
                pci_msi_domain_update_chip_ops(info);
 
+       info->flags |= MSI_FLAG_ACTIVATE_EARLY;
+
        domain = msi_create_irq_domain(fwnode, info, parent);
        if (!domain)
                return NULL;

diff --git a/include/linux/msi.h b/include/linux/msi.h
index 4f0bfe5912b2f1eb9be7a5c25f4e1ec64c2fafbe..e8c81fbd5f9cd11d4ac01adb929c7d1eee86e69e 100644 (file)
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -270,6 +270,8 @@ enum {
        MSI_FLAG_MULTI_PCI_MSI          = (1 << 2),
        /* Support PCI MSIX interrupts */
        MSI_FLAG_PCI_MSIX               = (1 << 3),
+       /* Needs early activate, required for PCI */
+       MSI_FLAG_ACTIVATE_EARLY         = (1 << 4),
 };
 
 int msi_domain_set_affinity(struct irq_data *data, const struct cpumask *mask,

diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
index 54999350162cbc89326a67a3728814e17871d784..19e9dfbe97fa53f732edd375cdd50341327750ac 100644 (file)
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -359,6 +359,17 @@ int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
                else
                        dev_dbg(dev, "irq [%d-%d] for MSI\n",
                                virq, virq + desc->nvec_used - 1);
+               /*
+                * This flag is set by the PCI layer as we need to activate
+                * the MSI entries before the PCI layer enables MSI in the
+                * card. Otherwise the card latches a random msi message.
+                */
+               if (info->flags & MSI_FLAG_ACTIVATE_EARLY) {
+                       struct irq_data *irq_data;
+
+                       irq_data = irq_domain_get_irq_data(domain, desc->irq);
+                       irq_domain_activate_irq(irq_data);
+               }
        }
 
        return 0;