APPLIED/Cmnts: [SRU][bionic/azure-4.15][PATCH 0/5] add x2apic support

[Krzysztof Kozlowski]

On 10/12/2021 18:40, Bartlomiej Zolnierkiewicz wrote:
> BugLink: https://bugs.launchpad.net/bugs/1951924
> 
> [SRU Justification]
> 
> [Impact]
> 
> Current linux-azure-4.15 kernel in bionic fails to boot Standard_M416s_v2 VM because of x2apic being disabled:
> 
> [ 0.000000] x2apic: IRQ remapping doesn't support X2APIC mode
> [ 0.000000] unchecked MSR access error: WRMSR to 0x1b (tried to write 0x00000000fee00100) at rIP: 0xffffffff9325d1f8 (native_write_msr+0x8/0x30)
> [ 0.000000] Call Trace:
> [ 0.000000] __x2apic_disable.part.5+0x49/0x80
> [ 0.000000] enable_IR_x2apic+0x123/0x18c
> [ 0.000000] default_setup_apic_routing+0x16/0x73
> [ 0.000000] apic_intr_mode_init+0x84/0x91
> [ 0.000000] x86_late_time_init+0x24/0x2b
> [ 0.000000] start_kernel+0x444/0x505
> [ 0.000000] x86_64_start_reservations+0x24/0x26
> [ 0.000000] x86_64_start_kernel+0x74/0x77
> [ 0.000000] secondary_startup_64+0xa5/0xb0
> [ 0.000000] x2apic disabled
> [ 0.000000] Switched APIC routing to physical flat.
> 
> [Test Plan]
> 
> Run updated kernel (with x2apic support backported from linux-azure-5.4 kernel).
> 
> It should boot fine and display:
> 
> [ 0.000000] Setting APIC routing to physical x2apic.
> 
> [Where problems could occur]
> 
> Potentially x2apic may now be used on other VM instances.
> 
> [Other Info]
> 
> None.


Applied with fixes:
1. Add "commit" to "backported from xxxx".
2. The same for cherry-picked. Please use `git cherry-pick -s -x` command.
3. Removal of second buglink and "cherry picked" from patch 5/5.


Best regards,
Krzysztof