[PATCH v2 0/3] kernel/resource: make walk_system_ram_res() and walk_mem_res() search the whole tree

[PATCH v2 0/3] kernel/resource: make walk_system_ram_res() and walk_mem_res() search the whole tree

[David Hildenbrand]

Playing with kdump+virtio-mem I noticed that kexec_file_load() does not
consider System RAM added via dax/kmem and virtio-mem when preparing the
elf header for kdump. Looking into the details, the logic used in
walk_system_ram_res() and walk_mem_res() seems to be outdated.

walk_system_ram_range() already does the right thing, let's change
walk_system_ram_res() and walk_mem_res(), and clean up.

Loading a kdump kernel via "kexec -p -s" ... will result in the kdump
kernel to also dump dax/kmem and virtio-mem added System RAM now.

Note: kexec-tools on x86-64 also have to be updated to consider this
memory in the kexec_load() case when processing /proc/iomem.

v1 -> v2:
- Added fixes tags to patch #1 and #2
- Refined the patch descriptions
- Added acks/rbs

David Hildenbrand (3):
  kernel/resource: make walk_system_ram_res() find all busy
    IORESOURCE_SYSTEM_RAM resources
  kernel/resource: make walk_mem_res() find all busy IORESOURCE_MEM
    resources
  kernel/resource: remove first_lvl / siblings_only logic

 kernel/resource.c | 45 ++++++++++++---------------------------------
 1 file changed, 12 insertions(+), 33 deletions(-)


base-commit: 0d02ec6b3136c73c09e7859f0d0e4e2c4c07b49b
-- 
2.29.2

[PATCH v2 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 system RAM (IORESOURCE_SYSTEM_RAM |
IORESOURCE_BUSY) only on the first level in the resource 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, for example,
inside device containers.

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 header, 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 IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY resources, making
the function behave like walk_system_ram_range().

Fixes: ebf71552bb0e ("virtio-mem: Add parent resource for all added "System RAM"")
Fixes: c221c0b0308f ("device-dax: "Hotplug" persistent memory for use like normal RAM")
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Dave Young <dyoung@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: x86@kernel.org
Cc: kexec@lists.infradead.org
Signed-off-by: David Hildenbrand <david@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

[PATCH v2 2/3] kernel/resource: make walk_mem_res() find all busy IORESOURCE_MEM resources

[David Hildenbrand]

It used to be true that we can have system RAM (IORESOURCE_SYSTEM_RAM |
IORESOURCE_BUSY) only on the first level in the resource 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, for example,
inside device containers.

IORESOURCE_SYSTEM_RAM is defined as IORESOURCE_MEM | IORESOURCE_SYSRAM
and just a special type of IORESOURCE_MEM.

The function walk_mem_res() only consideres the first level and is
used in arch/x86/mm/ioremap.c:__ioremap_check_mem() only. We currently
fail to identify System RAM added by dax/kmem and virtio-mem as
"IORES_MAP_SYSTEM_RAM", for example, allowing for remapping of such
"normal RAM" in __ioremap_caller().

Let's find all IORESOURCE_MEM | IORESOURCE_BUSY resources, making the
function behave similar to walk_system_ram_res().

Fixes: ebf71552bb0e ("virtio-mem: Add parent resource for all added "System RAM"")
Fixes: c221c0b0308f ("device-dax: "Hotplug" persistent memory for use like normal RAM")
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Dave Young <dyoung@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: x86@kernel.org
Cc: kexec@lists.infradead.org
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 kernel/resource.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 4efd6e912279..16e0c7e8ed24 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -470,7 +470,7 @@ int walk_mem_res(u64 start, u64 end, void *arg,
 {
 	unsigned long flags = IORESOURCE_MEM | 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

[PATCH v2 3/3] kernel/resource: remove first_lvl / siblings_only logic

[David Hildenbrand]

All functions that search for IORESOURCE_SYSTEM_RAM or IORESOURCE_MEM
resources now properly consider the whole resource tree, not just the first
level. Let's drop the unused first_lvl / siblings_only logic.

Remove documentation that indicates that some functions behave differently,
all consider the full resource tree now.

Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Dave Young <dyoung@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: x86@kernel.org
Cc: kexec@lists.infradead.org
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 kernel/resource.c | 45 ++++++++++++---------------------------------
 1 file changed, 12 insertions(+), 33 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 16e0c7e8ed24..7e00239a023a 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -64,12 +64,8 @@ static DEFINE_RWLOCK(resource_lock);
 static struct resource *bootmem_resource_free;
 static DEFINE_SPINLOCK(bootmem_resource_lock);
 
-static struct resource *next_resource(struct resource *p, bool sibling_only)
+static struct resource *next_resource(struct resource *p)
 {
-	/* Caller wants to traverse through siblings only */
-	if (sibling_only)
-		return p->sibling;
-
 	if (p->child)
 		return p->child;
 	while (!p->sibling && p->parent)
@@ -81,7 +77,7 @@ static void *r_next(struct seq_file *m, void *v, loff_t *pos)
 {
 	struct resource *p = v;
 	(*pos)++;
-	return (void *)next_resource(p, false);
+	return (void *)next_resource(p);
 }
 
 #ifdef CONFIG_PROC_FS
@@ -330,14 +326,10 @@ EXPORT_SYMBOL(release_resource);
  * of the resource that's within [@start..@end]; if none is found, returns
  * -ENODEV.  Returns -EINVAL for invalid parameters.
  *
- * This function walks the whole tree and not just first level children
- * unless @first_lvl is true.
- *
  * @start:	start address of the resource searched for
  * @end:	end address of same resource
  * @flags:	flags which the resource must have
  * @desc:	descriptor the resource must have
- * @first_lvl:	walk only the first level children, if set
  * @res:	return ptr, if resource found
  *
  * The caller must specify @start, @end, @flags, and @desc
@@ -345,9 +337,8 @@ EXPORT_SYMBOL(release_resource);
  */
 static int find_next_iomem_res(resource_size_t start, resource_size_t end,
 			       unsigned long flags, unsigned long desc,
-			       bool first_lvl, struct resource *res)
+			       struct resource *res)
 {
-	bool siblings_only = true;
 	struct resource *p;
 
 	if (!res)
@@ -358,7 +349,7 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
 
 	read_lock(&resource_lock);
 
-	for (p = iomem_resource.child; p; p = next_resource(p, siblings_only)) {
+	for (p = iomem_resource.child; p; p = next_resource(p)) {
 		/* If we passed the resource we are looking for, stop */
 		if (p->start > end) {
 			p = NULL;
@@ -369,13 +360,6 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
 		if (p->end < start)
 			continue;
 
-		/*
-		 * Now that we found a range that matches what we look for,
-		 * check the flags and the descriptor. If we were not asked to
-		 * use only the first level, start looking at children as well.
-		 */
-		siblings_only = first_lvl;
-
 		if ((p->flags & flags) != flags)
 			continue;
 		if ((desc != IORES_DESC_NONE) && (desc != p->desc))
@@ -402,14 +386,14 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
 
 static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
 				 unsigned long flags, unsigned long desc,
-				 bool first_lvl, void *arg,
+				 void *arg,
 				 int (*func)(struct resource *, void *))
 {
 	struct resource res;
 	int ret = -EINVAL;
 
 	while (start < end &&
-	       !find_next_iomem_res(start, end, flags, desc, first_lvl, &res)) {
+	       !find_next_iomem_res(start, end, flags, desc, &res)) {
 		ret = (*func)(&res, arg);
 		if (ret)
 			break;
@@ -431,7 +415,6 @@ static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
  * @arg: function argument for the callback @func
  * @func: callback function that is called for each qualifying resource area
  *
- * This walks through whole tree and not just first level children.
  * All the memory ranges which overlap start,end and also match flags and
  * desc are valid candidates.
  *
@@ -441,7 +424,7 @@ static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
 int walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start,
 		u64 end, void *arg, int (*func)(struct resource *, void *))
 {
-	return __walk_iomem_res_desc(start, end, flags, desc, false, arg, func);
+	return __walk_iomem_res_desc(start, end, flags, desc, arg, func);
 }
 EXPORT_SYMBOL_GPL(walk_iomem_res_desc);
 
@@ -457,8 +440,8 @@ 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, false,
-				     arg, func);
+	return __walk_iomem_res_desc(start, end, flags, IORES_DESC_NONE, arg,
+				     func);
 }
 
 /*
@@ -470,17 +453,14 @@ int walk_mem_res(u64 start, u64 end, void *arg,
 {
 	unsigned long flags = IORESOURCE_MEM | IORESOURCE_BUSY;
 
-	return __walk_iomem_res_desc(start, end, flags, IORES_DESC_NONE, false,
-				     arg, func);
+	return __walk_iomem_res_desc(start, end, flags, IORES_DESC_NONE, arg,
+				     func);
 }
 
 /*
  * This function calls the @func callback against all memory ranges of type
  * System RAM which are marked as IORESOURCE_SYSTEM_RAM and IORESOUCE_BUSY.
  * It is to be used only for System RAM.
- *
- * This will find System RAM ranges that are children of top-level resources
- * in addition to top-level System RAM resources.
  */
 int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
 			  void *arg, int (*func)(unsigned long, unsigned long, void *))
@@ -495,8 +475,7 @@ int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
 	end = ((u64)(start_pfn + nr_pages) << PAGE_SHIFT) - 1;
 	flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 	while (start < end &&
-	       !find_next_iomem_res(start, end, flags, IORES_DESC_NONE,
-				    false, &res)) {
+	       !find_next_iomem_res(start, end, flags, IORES_DESC_NONE, &res)) {
 		pfn = PFN_UP(res.start);
 		end_pfn = PFN_DOWN(res.end + 1);
 		if (end_pfn > pfn)
-- 
2.29.2