[PATCH 0/15][focal/linux-azure, jammy/linux-azure] Azure: Support multi-MSI

[Tim Gardner]

BugLink: https://bugs.launchpad.net/bugs/1981577

SRU Justification

[Impact]

The Hyper-V vPCI driver (pci-hyperv) doesn't work with a PCIe devcie that
supports multiple MSI interrupts (Note: MSI-X has been working fine). Recently
Jeffrey Hugo <quic_jhugo at quicinc.com> made 4 patches to the vPCI driver so
multiple-MSI can work now. Please consider picking up the 4 patches into the
linux-azure kernels for Ubuntu LTS 18.04, 20.04 and 22.04:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=08e61e861a0e47e5e1a3fb78406afd6b0cea6b6d
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=455880dfe292a2bdd3b4ad6a107299fce610e64b
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b4b77778ecc5bfbd4e77de1b2fd5c1dd3c655f1f
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a2bad844a67b1c7740bda63e87453baf63c3a7f7

Microsoft is working to bring up a Qualcomm PCIe device to Linux VMs running
on Azure. We need the 4 patches for the device to work on Azure/Hyper-V.

The 5.4 kernel patches are a mix of cherry picks and backports since cherry picking scaffold
patches would have been too intrusive, whereas for the 5.15 kernel I chose
some scaffolding patches in order to have all clean cherry picks.

[Test Plan]

Microsoft tested both 5.4 and 5.15 kernels.

[Where things could go wrong]

MSI vectors could be mis-wired or ignored.

[Other Info]

SF: #00339521