PCI: hv: Reuse existing IRTE allocation in compose_msi_msg()
authorJeffrey Hugo <quic_jhugo@quicinc.com>
Wed, 11 May 2022 15:23:02 +0000 (09:23 -0600)
committerWei Liu <wei.liu@kernel.org>
Wed, 11 May 2022 17:50:20 +0000 (17:50 +0000)
commitb4b77778ecc5bfbd4e77de1b2fd5c1dd3c655f1f
treec6ec67092f9314054fb3c6ccc76f65d0fc47ffe9
parentac6811a9b36f3ceb549d8b84bd8aeedf6026df02
PCI: hv: Reuse existing IRTE allocation in compose_msi_msg()

Currently if compose_msi_msg() is called multiple times, it will free any
previous IRTE allocation, and generate a new allocation.  While nothing
prevents this from occurring, it is extraneous when Linux could just reuse
the existing allocation and avoid a bunch of overhead.

However, when future IRTE allocations operate on blocks of MSIs instead of
a single line, freeing the allocation will impact all of the lines.  This
could cause an issue where an allocation of N MSIs occurs, then some of
the lines are retargeted, and finally the allocation is freed/reallocated.
The freeing of the allocation removes all of the configuration for the
entire block, which requires all the lines to be retargeted, which might
not happen since some lines might already be unmasked/active.

Signed-off-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Tested-by: Dexuan Cui <decui@microsoft.com>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1652282582-21595-1-git-send-email-quic_jhugo@quicinc.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
drivers/pci/controller/pci-hyperv.c