[PATCH v1 1/3] kernel/resource: make walk_system_ram_res() find all busy IORESOURCE_SYSTEM_RAM resources

[David Hildenbrand]

It used to be true that we can have busy system RAM only on the first level
in the resourc tree. However, this is no longer holds for driver-managed
system RAM (i.e., added via dax/kmem and virtio-mem), which gets added on
lower levels.

We have two users of walk_system_ram_res(), which currently only
consideres the first level:
a) kernel/kexec_file.c:kexec_walk_resources() -- We properly skip
   IORESOURCE_SYSRAM_DRIVER_MANAGED resources via
   locate_mem_hole_callback(), so even after this change, we won't be
   placing kexec images onto dax/kmem and virtio-mem added memory. No
   change.
b) arch/x86/kernel/crash.c:fill_up_crash_elf_data() -- we're currently
   not adding relevant ranges to the crash elf info, resulting in them
   not getting dumped via kdump.

This change fixes loading a crashkernel via kexec_file_load() and including
dax/kmem and virtio-mem added System RAM in the crashdump on x86-64. Note
that e.g,, arm64 relies on memblock data and, therefore, always considers
all added System RAM already.

Let's find all busy IORESOURCE_SYSTEM_RAM resources, making the function
behave like walk_system_ram_range().

Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Cc: Dan Williams <dan.j.williams at intel.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
Cc: Mauro Carvalho Chehab <mchehab+huawei at kernel.org>
Cc: Signed-off-by: David Hildenbrand <david at redhat.com>
Cc: Dave Young <dyoung at redhat.com>
Cc: Baoquan He <bhe at redhat.com>
Cc: Vivek Goyal <vgoyal at redhat.com>
Cc: Dave Hansen <dave.hansen at linux.intel.com>
Cc: Keith Busch <keith.busch at intel.com>
Cc: Michal Hocko <mhocko at suse.com>
Cc: Qian Cai <cai at lca.pw>
Cc: Oscar Salvador <osalvador at suse.de>
Cc: Eric Biederman <ebiederm at xmission.com>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Ingo Molnar <mingo at redhat.com>
Cc: Borislav Petkov <bp at alien8.de>
Cc: "H. Peter Anvin" <hpa at zytor.com>
Cc: Tom Lendacky <thomas.lendacky at amd.com>
Cc: Brijesh Singh <brijesh.singh at amd.com>
Cc: x86 at kernel.org
Cc: kexec at lists.infradead.org
Signed-off-by: David Hildenbrand <david at redhat.com>
---
 kernel/resource.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 627e61b0c124..4efd6e912279 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -457,7 +457,7 @@ int walk_system_ram_res(u64 start, u64 end, void *arg,
 {
 	unsigned long flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 
-	return __walk_iomem_res_desc(start, end, flags, IORES_DESC_NONE, true,
+	return __walk_iomem_res_desc(start, end, flags, IORES_DESC_NONE, false,
 				     arg, func);
 }
 
-- 
2.29.2