The following commit has been merged into the irq/core branch of tip:

Commit-ID: 438553958ba19296663c6d6583d208dfb6792830 Gitweb: https://git.kernel.org/tip/438553958ba19296663c6d6583d208dfb6792830 Author: Thomas Gleixner tglx@linutronix.de AuthorDate: Thu, 29 Jul 2021 23:51:40 +02:00 Committer: Thomas Gleixner tglx@linutronix.de CommitterDate: Tue, 10 Aug 2021 10:59:20 +02:00

PCI/MSI: Enable and mask MSI-X early

The ordering of MSI-X enable in hardware is dysfunctional:

1) MSI-X is disabled in the control register 2) Various setup functions 3) pci_msi_setup_msi_irqs() is invoked which ends up accessing the MSI-X table entries 4) MSI-X is enabled and masked in the control register with the comment that enabling is required for some hardware to access the MSI-X table

Step #4 obviously contradicts #3. The history of this is an issue with the NIU hardware. When #4 was introduced the table access actually happened in msix_program_entries() which was invoked after enabling and masking MSI-X.

This was changed in commit d71d6432e105 ("PCI/MSI: Kill redundant call of irq_set_msi_desc() for MSI-X interrupts") which removed the table write from msix_program_entries().

Interestingly enough nobody noticed and either NIU still works or it did not get any testing with a kernel 3.19 or later.

Nevertheless this is inconsistent and there is no reason why MSI-X can't be enabled and masked in the control register early on, i.e. move step #4 above to step #1. This preserves the NIU workaround and has no side effects on other hardware.

Fixes: d71d6432e105 ("PCI/MSI: Kill redundant call of irq_set_msi_desc() for MSI-X interrupts") Signed-off-by: Thomas Gleixner tglx@linutronix.de Tested-by: Marc Zyngier maz@kernel.org Reviewed-by: Ashok Raj ashok.raj@intel.com Reviewed-by: Marc Zyngier maz@kernel.org Acked-by: Bjorn Helgaas bhelgaas@google.com Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210729222542.344136412@linutronix.de

--- drivers/pci/msi.c | 28 +++++++++++++++------------- 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c index 9232255..5d39ed8 100644 --- a/drivers/pci/msi.c +++ b/drivers/pci/msi.c @@ -772,18 +772,25 @@ static int msix_capability_init(struct pci_dev *dev, struct msix_entry *entries, u16 control; void __iomem *base;

- /* Ensure MSI-X is disabled while it is set up */ - pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0); + /* + * Some devices require MSI-X to be enabled before the MSI-X + * registers can be accessed. Mask all the vectors to prevent + * interrupts coming in before they're fully set up. + */ + pci_msix_clear_and_set_ctrl(dev, 0, PCI_MSIX_FLAGS_MASKALL | + PCI_MSIX_FLAGS_ENABLE);

pci_read_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, &control); /* Request & Map MSI-X table region */ base = msix_map_region(dev, msix_table_size(control)); - if (!base) - return -ENOMEM; + if (!base) { + ret = -ENOMEM; + goto out_disable; + }

ret = msix_setup_entries(dev, base, entries, nvec, affd); if (ret) - return ret; + goto out_disable;

ret = pci_msi_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSIX); if (ret) @@ -794,14 +801,6 @@ static int msix_capability_init(struct pci_dev *dev, struct msix_entry *entries, if (ret) goto out_free;

- /* - * Some devices require MSI-X to be enabled before we can touch the - * MSI-X registers. We need to mask all the vectors to prevent - * interrupts coming in before they're fully set up. - */ - pci_msix_clear_and_set_ctrl(dev, 0, - PCI_MSIX_FLAGS_MASKALL | PCI_MSIX_FLAGS_ENABLE); - msix_program_entries(dev, entries);

ret = populate_msi_sysfs(dev); @@ -836,6 +835,9 @@ out_avail: out_free: free_msi_irqs(dev);

+out_disable: + pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0); + return ret; }