Re: [PATCH] x86: Fix an issue with invalid ACPI numa config

[Jonathan Cameron <jonathan.cameron@huawei.com>]

On Thu, 15 Nov 2018 11:06:17 +0000
Jonathan Cameron <Jonathan.Cameron@huawei.com> wrote:

> The addition of support to read the numa node for a PCI
> card specified by _PXM resulted in Martin's system not
> booting.   Looking at the ACPI tables it seems that there
> are PXM entries for the root ports, but no SRAT table.
> 
> The absence of SRAT table results in dummy_numa_init being
> called.  However, unlike on arm64, this doesn't then result
> in numa_off being set.  When the PCI code later comes along
> and calls acpi_get_node for any PCI card below the root port,
> it navigates up the ACPI tree until it finds the PXM value in
> the root port. This value is then passed to
> acpi_map_pxm_to_node.  If numa_off is set this returns,
> NUMA_NO_NODE (as it does on arm64), on x86 it instead tries
> to allocate a numa node from the unused set without setting
> up all the infrastructure that would normally accompany such
> a call.  We have not identified exactly which driver is
> causing the subsequent hang for Martin.
> 
> It is invalid under the ACPI spec to specify new
> numa nodes using PXM if they have no presence in SRAT.
> Thus the simplest fix is to set numa_off when it is off due
> to an invalid SRAT (here not present at all).
> 
> I do not have easy access to appropriate x86 numa systems so
> would appreciate some testing of this one!
> 
> Known problem boards setups:
> 
> AMD Ryzen Threadripper 2950X on ASROCK X399 TAICHI
> MSI X399 SLI PLUS (probably - not confirmed yet)
> 
> The PCI patch has been reverted, so this fix is not critical.
> 
> Reported-by: Martin Hundeb�ll <martin@geanix.com>
Sorry, seems I had a wrong encoding somewhere down the line and it messed
up Martin's name.  Could we fix that if applying!

> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Fixes: bad7dcd94f39 ("ACPI/PCI: Pay attention to device-specific _PXM node values")
> 
> ---
>  arch/x86/mm/numa.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> index 1308f5408bf7..ce1182f953ff 100644
> --- a/arch/x86/mm/numa.c
> +++ b/arch/x86/mm/numa.c
> @@ -695,6 +695,8 @@ static int __init dummy_numa_init(void)
>  	node_set(0, numa_nodes_parsed);
>  	numa_add_memblk(0, 0, PFN_PHYS(max_pfn));
>  
> +	numa_off = true;
> +
>  	return 0;
>  }
>