PCI: hv: Reuse existing IRTE allocation in compose_msi_msg()

stable inclusion
from stable-v5.10.134
commit 522bd31d6b4bb783e4454d8f11d012e77c627648
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5ZVR7

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=522bd31d6b4bb783e4454d8f11d012e77c627648



--------------------------------

commit b4b77778 upstream.

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>
Signed-off-by: Carl Vanderlip <quic_carlv@quicinc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>