[Patch 0/2 v2] [impish/linux-azure] Azure: not enough RAM under 4GB for CVM

[Tim Gardner]

v2 - attach the 2nd patch which was forgotten the first time.

SRU Justification

[Impact]
Can you please include one more patchset for the "no enough RAM under 4GB" issue
for the v5.13 kernel (and v5.15 kernel):
https://lwn.net/ml/linux-kernel/20220209122302.213882-2-ltykernel@gmail.com/
https://lwn.net/ml/linux-kernel/20220209122302.213882-3-ltykernel@gmail.com/

Without the two patches, currently the 5.13 kernel (and 5.15 kernel) can't boot
as a CVM guest on Azure. :-(

The background is: currently an Azure host only provides about 900 MB memory below
the 4GB boundary while the swiotlb code (which is required by the CVM patchset)
needs to allocate memory of a size of MIN(1GB, 6% of the total memory). There will
be an Azure host update, with which the host will provide about 3GB memory below
the 4GB boundary, but we still need to wait a few more weeks to know the ETA.
Currently the above two patches can work around the issue from the guest side.

[Test Case]

Microsoft tested

[Where things could go wrong]

These patches could affect non-CVM instances.

[Other Info]

SF: #00323683