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genirq/msi: Provide MSI_FLAG_MSIX_ALLOC_DYN

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Provide a new MSI feature flag in preparation for dynamic MSIX allocation
after the initial MSI-X enable has been done.

This needs to be an explicit MSI interrupt domain feature because quite
some implementations (both interrupt domains and legacy allocation mode)
have clear expectations that the allocation code is only invoked when MSI-X
is about to be enabled. They either talk to hypervisors or do some other
work and are not prepared to be invoked on an already MSI-X enabled device.

This is also explicit MSI-X only because rewriting the size of the MSI
entries is only possible when disabling MSI which in turn might cause lost
interrupts on the device.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221124232326.558843119@linutronix.de
This commit is contained in:
Thomas Gleixner 2022-11-25 00:26:20 +01:00
parent 3d393b2174
commit b834e3c08f
1 changed files with 2 additions and 1 deletions
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3
include/linux/msi.h
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@ -557,7 +557,8 @@ enum {
MSI_FLAG_LEVEL_CAPABLE = (1 << 18),
/* MSI-X entries must be contiguous */
MSI_FLAG_MSIX_CONTIGUOUS = (1 << 19),
/* PCI/MSI-X vectors can be dynamically allocated/freed post MSI-X enable */
MSI_FLAG_PCI_MSIX_ALLOC_DYN = (1 << 20),
};
/**