[Bug 1911205] [NEW] Revert or drop obsolete patches for PCI

Public bug reported:

[Impact]

In both 5.4 and 5.8 kernel, there are two patches in PCI to workaround
an issue with GPU and Infiniband at the time. Those two patches are no
longer necessary in today's Azure environment. Those two patches
introduces bugs to the latest Azure HPC VM SKU.

4.15 kernel is not affected.

Microsoft has regression tested and verified that the following two
patches can be dropped or reverted in 5.4 and 5.8.

5.4 kernel:
Patch 1: Revert "PCI: hv: Make sure the bus domain is really unique"
https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-azure/+git/bionic/commit/drivers/pci/controller/pci-hyperv.c?h=azure-5.4&id=faf2750396d60001046333bd46eee757bb4cac7b

Patch 2: UBUNTU: SAUCE: pci-hyperv: Use only 16 bit integer for PCI domain
https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-azure/+git/bionic/commit/drivers/pci/controller/pci-hyperv.c?h=azure-5.4&id=04ac3e06ab708131c1c18cb7db10ca5dd6feedce

5.8 kernel:
Patch 1: Revert "PCI: hv: Make sure the bus domain is really unique"
https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-azure/+git/groovy/commit/drivers/pci/controller/pci-hyperv.c?h=Ubuntu-azure-5.8.0-1016.17&id=7c85402203e26d4d0474f69b99b5a06ffb765630

Patch 2: UBUNTU: SAUCE: pci-hyperv: Use only 16 bit integer for PCI domain
https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-azure/+git/groovy/commit/drivers/pci/controller/pci-hyperv.c?h=Ubuntu-azure-5.8.0-1016.17&id=b72f314d15ab0ad7b80b761d8167962300c1bd35

[Test Case]

As per #1816106, instances with multiple GPUs should still be able to
see all of them.

[Where problems could occur]

Issues or oops in instances types with multiple GPUs.

** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: Marcelo Cerri (mhcerri)
Status: New

** Affects: linux (Ubuntu Focal)
Importance: Undecided
Status: In Progress

** Affects: linux (Ubuntu Groovy)
Importance: Undecided
Status: In Progress

** Also affects: linux (Ubuntu Groovy)
Importance: Undecided
Status: New

** Also affects: linux (Ubuntu Focal)
Importance: Undecided
Status: New

** Changed in: linux (Ubuntu Focal)
Status: New => In Progress

** Changed in: linux (Ubuntu Groovy)
Status: New => In Progress

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https://bugs.launchpad.net/bugs/1911205

Title:
Revert or drop obsolete patches for PCI

Status in linux package in Ubuntu:
New
Status in linux source package in Focal:
In Progress
Status in linux source package in Groovy:
In Progress

Bug description:
[Impact]

In both 5.4 and 5.8 kernel, there are two patches in PCI to workaround
an issue with GPU and Infiniband at the time. Those two patches are no
longer necessary in today's Azure environment. Those two patches
introduces bugs to the latest Azure HPC VM SKU.

4.15 kernel is not affected.

Microsoft has regression tested and verified that the following two
patches can be dropped or reverted in 5.4 and 5.8.

5.4 kernel:
Patch 1: Revert "PCI: hv: Make sure the bus domain is really unique"
https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-azure/+git/bionic/commit/drivers/pci/controller/pci-hyperv.c?h=azure-5.4&id=faf2750396d60001046333bd46eee757bb4cac7b

Patch 2: UBUNTU: SAUCE: pci-hyperv: Use only 16 bit integer for PCI domain
https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-azure/+git/bionic/commit/drivers/pci/controller/pci-hyperv.c?h=azure-5.4&id=04ac3e06ab708131c1c18cb7db10ca5dd6feedce

5.8 kernel:
Patch 1: Revert "PCI: hv: Make sure the bus domain is really unique"
https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-azure/+git/groovy/commit/drivers/pci/controller/pci-hyperv.c?h=Ubuntu-azure-5.8.0-1016.17&id=7c85402203e26d4d0474f69b99b5a06ffb765630

Patch 2: UBUNTU: SAUCE: pci-hyperv: Use only 16 bit integer for PCI domain
https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-azure/+git/groovy/commit/drivers/pci/controller/pci-hyperv.c?h=Ubuntu-azure-5.8.0-1016.17&id=b72f314d15ab0ad7b80b761d8167962300c1bd35

[Test Case]

As per #1816106, instances with multiple GPUs should still be able to
see all of them.

[Where problems could occur]

Issues or oops in instances types with multiple GPUs.

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