Question: Enable LINUX_EFI_MEMRESERVE_TABLE_GUID in EFI

[Leo Yan <leo.yan@xxxxxxxxxx>]

Hi there,

Now I am working on Ampere Altra SoC platform, with Xen (4.16) and Linux
kernel (5.15.23).

I observed a warning is reported by Linux kernel in the booting flow:

[    0.403737] ------------[ cut here ]------------
[    0.403738] WARNING: CPU: 30 PID: 0 at drivers/irqchip/irq-gic-v3-its.c:3074 
its_cpu_init+0x814/0xae0
[    0.403745] Modules linked in:
[    0.403748] CPU: 30 PID: 0 Comm: swapper/30 Tainted: G        W         
5.15.23-ampere-lts-standard #1
[    0.403752] pstate: 600001c5 (nZCv dAIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[    0.403755] pc : its_cpu_init+0x814/0xae0
[    0.403758] lr : its_cpu_init+0x810/0xae0
[    0.403761] sp : ffff800009c03ce0
[    0.403762] x29: ffff800009c03ce0 x28: 000000000000001e x27: ffff880711f43000
[    0.403767] x26: ffff80000a3c0070 x25: fffffc1ffe0a4400 x24: ffff80000a3c0000
[    0.403770] x23: ffff8000095bc998 x22: ffff8000090a6000 x21: ffff800009850cb0
[    0.403774] x20: ffff800009701a10 x19: ffff800009701000 x18: ffffffffffffffff
[    0.403777] x17: 3030303035303031 x16: 3030313030303078 x15: 303a30206e6f6967
[    0.403780] x14: 6572206530312072 x13: 3030303030353030 x12: 3130303130303030
[    0.403784] x11: 78303a30206e6f69 x10: 6765722065303120 x9 : ffff80000870e710
[    0.403788] x8 : 6964657220646e75 x7 : 0000000000000003 x6 : 0000000000000000
[    0.403791] x5 : 0000000000000000 x4 : fffffc0000000000 x3 : 0000000000000010
[    0.403794] x2 : 000000000000ffff x1 : 0000000000010000 x0 : 00000000ffffffed
[    0.403798] Call trace:
[    0.403799]  its_cpu_init+0x814/0xae0
[    0.403802]  gic_starting_cpu+0x48/0x90
[    0.403805]  cpuhp_invoke_callback+0x16c/0x5b0
[    0.403808]  cpuhp_invoke_callback_range+0x78/0xf0
[    0.403811]  notify_cpu_starting+0xbc/0xdc
[    0.403814]  secondary_start_kernel+0xe0/0x170
[    0.403817]  __secondary_switched+0x94/0x98
[    0.403821] ---[ end trace f68728a0d3053b70 ]---

Looked into the code, the GICv3 driver tries to create persistent
reservations for pending pages, and the persistent reservation table
can be used by kexec/kdump.  For the persistent reservations, it
relies on MEMRESERVE EFI configuration table, but this table is not
supported by xen.efi, I think this is the reason for the above oops.

I checked that if I boot a host Linux (without Xen), then the EFI has
provided MEMRESERVE configuration table, I can get below log:

  #  dmesg | grep MEMRESERVE
  [    0.000000] efi: TPMFinalLog=0x807f9ef0000 ACPI 2.0=0x807fa0d0018 ... 
MEMRESERVE=0x807f8141e98

Just want to confirm, is anyone working on enabling MEMRESERVE EFI
configuration table for Xen?  And welcome any comments and
suggestions!

Thanks,
Leo