From: Dexuan Cui <decui@microsoft.com>
Sent: Monday, November 2, 2020 5:12 PM

...

Hi tglx,
Now this patch is in the x86/apic branch, which is great! Thanks for the 
quick action! But the third line of the below paragraph of the commit log
is missing... Sorry I just realized I should have not prefixed that line with the
">255 APIC IDs" -- it looks a line is ignored if it starts with 2 chars of ">>". :-(

On an old Hyper-V host that doesn't support the Extended Dest ID, nothing
changes with this commit: Linux VM is still able to bring up the CPUs with

quoted

255 APIC IDs with the help of hyperv-iommu.c, but IOAPIC interrupts still

can not go to such CPUs, and the kdump kernel still can not work properly
on such CPUs.