[PATCH 4/5] resource: Report parent to walk_iomem_res_desc() callback

[Dan Williams]

In support of detecting whether a resource might have been been claimed,
report the parent to the walk_iomem_res_desc() callback. For example,
the ACPI HMAT parser publishes "hmem" platform devices per target range.
However, if the HMAT is disabled / missing a fallback driver can attach
devices to the raw memory ranges as a fallback if it sees unclaimed /
orphan "Soft Reserved" resources in the resource tree.
Otherwise, find_next_iomem_res() returns a resource with garbage data
from the stack allocation in __walk_iomem_res_desc() for the res->parent
field.

Just wondering if we shouldn't just copy the complete resource struct and
just override the start and end values? That way, if some code in the
future wants to look at sibling or child values, another change isn't needed.
Just a thought.

Thanks for taking a look. I think it's ok to come update this again if
that need arises.

[Dan Williams]

Disable parsing of the HMAT for debug, to workaround broken platform
instances, or cases where it is otherwise not wanted.

Rafael, any heartburn with this change to the numa= option?

...as I look at this I realize I failed to also update
Documentation/x86/x86_64/boot-options.rst, will fix.

---
arch/x86/mm/numa.c | 4 ++++
drivers/acpi/numa/hmat.c | 3 ++-
include/acpi/acpi_numa.h | 1 +
3 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index 59ba008504dc..22de2e2610c1 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -44,6 +44,10 @@ static __init int numa_setup(char *opt)
#ifdef CONFIG_ACPI_NUMA
if (!strncmp(opt, "noacpi", 6))
acpi_numa = -1;
+#ifdef CONFIG_ACPI_HMAT
+ if (!strncmp(opt, "nohmat", 6))
+ hmat_disable = 1;
+#endif
#endif
return 0;
}
diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
index 2c32cfb72370..d3db121e393a 100644
--- a/drivers/acpi/numa/hmat.c
+++ b/drivers/acpi/numa/hmat.c
@@ -26,6 +26,7 @@
#include <linux/sysfs.h>
static u8 hmat_revision;
+int hmat_disable __initdata;
static LIST_HEAD(targets);
static LIST_HEAD(initiators);
@@ -814,7 +815,7 @@ static __init int hmat_init(void)
enum acpi_hmat_type i;
acpi_status status;
- if (srat_disabled())
+ if (srat_disabled() || hmat_disable)
return 0;
status = acpi_get_table(ACPI_SIG_SRAT, 0, &tbl);
diff --git a/include/acpi/acpi_numa.h b/include/acpi/acpi_numa.h
index fdebcfc6c8df..48ca468e9b61 100644
--- a/include/acpi/acpi_numa.h
+++ b/include/acpi/acpi_numa.h
@@ -18,6 +18,7 @@ extern int node_to_pxm(int);
extern int acpi_map_pxm_to_node(int);
extern unsigned char acpi_srat_revision;
extern int acpi_numa __initdata;
+extern int hmat_disable __initdata;
extern void bad_srat(void);
extern int srat_disabled(void);