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xen/boot: Disable NUMA for PV guests.
The hypervisor is in charge of allocating the proper "NUMA" memory and dealing with the CPU scheduler to keep them bound to the proper NUMA node. The PV guests (and PVHVM) have no inkling of where they run and do not need to know that right now. In the future we will need to inject NUMA configuration data (if a guest spans two or more NUMA nodes) so that the kernel can make the right choices. But those patches are not yet present. In the meantime, disable the NUMA capability in the PV guest, which also fixes a bootup issue. Andre says: "we see Dom0 crashes due to the kernel detecting the NUMA topology not by ACPI, but directly from the northbridge (CONFIG_AMD_NUMA). This will detect the actual NUMA config of the physical machine, but will crash about the mismatch with Dom0's virtual memory. Variation of the theme: Dom0 sees what it's not supposed to see. This happens with the said config option enabled and on a machine where this scanning is still enabled (K8 and Fam10h, not Bulldozer class) We have this dump then: NUMA: Warning: node ids are out of bound, from=-1 to=-1 distance=10 Scanning NUMA topology in Northbridge 24 Number of physical nodes 4 Node 0 MemBase 0000000000000000 Limit 0000000040000000 Node 1 MemBase 0000000040000000 Limit 0000000138000000 Node 2 MemBase 0000000138000000 Limit 00000001f8000000 Node 3 MemBase 00000001f8000000 Limit 0000000238000000 Initmem setup node 0 0000000000000000-0000000040000000 NODE_DATA [000000003ffd9000 - 000000003fffffff] Initmem setup node 1 0000000040000000-0000000138000000 NODE_DATA [0000000137fd9000 - 0000000137ffffff] Initmem setup node 2 0000000138000000-00000001f8000000 NODE_DATA [00000001f095e000 - 00000001f0984fff] Initmem setup node 3 00000001f8000000-0000000238000000 Cannot find 159744 bytes in node 3 BUG: unable to handle kernel NULL pointer dereference at (null) IP: [<ffffffff81d220e6>] __alloc_bootmem_node+0x43/0x96 Pid: 0, comm: swapper Not tainted 3.3.6 #1 AMD Dinar/Dinar RIP: e030:[<ffffffff81d220e6>] [<ffffffff81d220e6>] __alloc_bootmem_node+0x43/0x96 .. snip.. [<ffffffff81d23024>] sparse_early_usemaps_alloc_node+0x64/0x178 [<ffffffff81d23348>] sparse_init+0xe4/0x25a [<ffffffff81d16840>] paging_init+0x13/0x22 [<ffffffff81d07fbb>] setup_arch+0x9c6/0xa9b [<ffffffff81683954>] ? printk+0x3c/0x3e [<ffffffff81d01a38>] start_kernel+0xe5/0x468 [<ffffffff81d012cf>] x86_64_start_reservations+0xba/0xc1 [<ffffffff81007153>] ? xen_setup_runstate_info+0x2c/0x36 [<ffffffff81d050ee>] xen_start_kernel+0x565/0x56c " so we just disable NUMA scanning by setting numa_off=1. CC: stable@vger.kernel.org Reported-and-Tested-by:Andre Przywara <andre.przywara@amd.com> Acked-by: