7e90e81a4b
commit 438553958ba19296663c6d6583d208dfb6792830 upstream.
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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
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