On Wed, Jul 13, 2016 at 05:18:33PM +0100, Marc Zyngier wrote:
> 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.
>
> Reported-by: Bharat Kumar Gogada <bharat.kumar.gogada@xxxxxxxxxx>
> Tested-by: Bharat Kumar Gogada <bharat.kumar.gogada@xxxxxxxxxx>
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Thomas, let me know if you'd like me to take this. It looks like the
real smarts here are in kernel/irq, so I assume you'll take it unless
I hear otherwise.
> ---
> drivers/pci/msi.c | 2 ++
> include/linux/msi.h | 2 ++
> kernel/irq/msi.c | 7 +++++++
> 3 files changed, 11 insertions(+)
>
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index a080f44..565e2a4 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -1277,6 +1277,8 @@ 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 8b425c6..513b7c7 100644
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -270,6 +270,8 @@ enum {
> MSI_FLAG_MULTI_PCI_MSI = (1 << 3),
> /* Support PCI MSIX interrupts */
> MSI_FLAG_PCI_MSIX = (1 << 4),
> + /* Needs early activate, required for PCI */
> + MSI_FLAG_ACTIVATE_EARLY = (1 << 5),
> };
>
> 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 38e89ce..4ed2cca 100644
> --- a/kernel/irq/msi.c
> +++ b/kernel/irq/msi.c
> @@ -361,6 +361,13 @@ 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);
> +
> + 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;
> --
> 2.1.4
>
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