From: Dan Williams <dan.j.williams@intel.com>
Insert Soft Reserved memory into a dedicated soft_reserve_resource tree
instead of the iomem_resource tree at boot. Delay publishing these ranges
into the iomem hierarchy until ownership is resolved and the HMEM path
is ready to consume them.
Publishing Soft Reserved ranges into iomem too early conflicts with CXL
hotplug and prevents region assembly when those ranges overlap CXL
windows.
Follow up patches will reinsert Soft Reserved ranges into iomem after CXL
window publication is complete and HMEM is ready to claim the memory. This
provides a cleaner handoff between EFI-defined memory ranges and CXL
resource management without trimming or deleting resources later.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
---
arch/x86/kernel/e820.c | 2 +-
drivers/cxl/acpi.c | 2 +-
drivers/dax/hmem/device.c | 4 +-
drivers/dax/hmem/hmem.c | 7 ++-
include/linux/ioport.h | 13 +++++-
kernel/resource.c | 92 +++++++++++++++++++++++++++++++++------
6 files changed, 100 insertions(+), 20 deletions(-)
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index c3acbd26408b..c32f144f0e4a 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -1153,7 +1153,7 @@ void __init e820__reserve_resources_late(void)
res = e820_res;
for (i = 0; i < e820_table->nr_entries; i++) {
if (!res->parent && res->end)
- insert_resource_expand_to_fit(&iomem_resource, res);
+ insert_resource_expand_to_fit(res);
res++;
}
diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index bd2e282ca93a..b37858f797be 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -847,7 +847,7 @@ static int add_cxl_resources(struct resource *cxl_res)
*/
cxl_set_public_resource(res, new);
- insert_resource_expand_to_fit(&iomem_resource, new);
+ __insert_resource_expand_to_fit(&iomem_resource, new);
next = res->sibling;
while (next && resource_overlaps(new, next)) {
diff --git a/drivers/dax/hmem/device.c b/drivers/dax/hmem/device.c
index f9e1a76a04a9..22732b729017 100644
--- a/drivers/dax/hmem/device.c
+++ b/drivers/dax/hmem/device.c
@@ -83,8 +83,8 @@ static __init int hmem_register_one(struct resource *res, void *data)
static __init int hmem_init(void)
{
- walk_iomem_res_desc(IORES_DESC_SOFT_RESERVED,
- IORESOURCE_MEM, 0, -1, NULL, hmem_register_one);
+ walk_soft_reserve_res_desc(IORES_DESC_SOFT_RESERVED, IORESOURCE_MEM, 0,
+ -1, NULL, hmem_register_one);
return 0;
}
diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
index c18451a37e4f..48f4642f4bb8 100644
--- a/drivers/dax/hmem/hmem.c
+++ b/drivers/dax/hmem/hmem.c
@@ -73,11 +73,14 @@ static int hmem_register_device(struct device *host, int target_nid,
return 0;
}
- rc = region_intersects(res->start, resource_size(res), IORESOURCE_MEM,
- IORES_DESC_SOFT_RESERVED);
+ rc = region_intersects_soft_reserve(res->start, resource_size(res),
+ IORESOURCE_MEM,
+ IORES_DESC_SOFT_RESERVED);
if (rc != REGION_INTERSECTS)
return 0;
+ /* TODO: Add Soft-Reserved memory back to iomem */
+
id = memregion_alloc(GFP_KERNEL);
if (id < 0) {
dev_err(host, "memregion allocation failure for %pr\n", res);
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index e8b2d6aa4013..e20226870a81 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -232,6 +232,9 @@ struct resource_constraint {
/* PC/ISA/whatever - the normal PC address spaces: IO and memory */
extern struct resource ioport_resource;
extern struct resource iomem_resource;
+#ifdef CONFIG_EFI_SOFT_RESERVE
+extern struct resource soft_reserve_resource;
+#endif
extern struct resource *request_resource_conflict(struct resource *root, struct resource *new);
extern int request_resource(struct resource *root, struct resource *new);
@@ -242,7 +245,8 @@ extern void reserve_region_with_split(struct resource *root,
const char *name);
extern struct resource *insert_resource_conflict(struct resource *parent, struct resource *new);
extern int insert_resource(struct resource *parent, struct resource *new);
-extern void insert_resource_expand_to_fit(struct resource *root, struct resource *new);
+extern void __insert_resource_expand_to_fit(struct resource *root, struct resource *new);
+extern void insert_resource_expand_to_fit(struct resource *new);
extern int remove_resource(struct resource *old);
extern void arch_remove_reservations(struct resource *avail);
extern int allocate_resource(struct resource *root, struct resource *new,
@@ -409,6 +413,13 @@ walk_system_ram_res_rev(u64 start, u64 end, void *arg,
extern int
walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start, u64 end,
void *arg, int (*func)(struct resource *, void *));
+extern int
+walk_soft_reserve_res_desc(unsigned long desc, unsigned long flags,
+ u64 start, u64 end, void *arg,
+ int (*func)(struct resource *, void *));
+extern int
+region_intersects_soft_reserve(resource_size_t start, size_t size,
+ unsigned long flags, unsigned long desc);
struct resource *devm_request_free_mem_region(struct device *dev,
struct resource *base, unsigned long size);
diff --git a/kernel/resource.c b/kernel/resource.c
index b9fa2a4ce089..208eaafcc681 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -321,13 +321,14 @@ static bool is_type_match(struct resource *p, unsigned long flags, unsigned long
}
/**
- * find_next_iomem_res - Finds the lowest iomem resource that covers part of
- * [@start..@end].
+ * find_next_res - Finds the lowest resource that covers part of
+ * [@start..@end].
*
* If a resource is found, returns 0 and @*res is overwritten with the part
* of the resource that's within [@start..@end]; if none is found, returns
* -ENODEV. Returns -EINVAL for invalid parameters.
*
+ * @parent: resource tree root to search
* @start: start address of the resource searched for
* @end: end address of same resource
* @flags: flags which the resource must have
@@ -337,9 +338,9 @@ static bool is_type_match(struct resource *p, unsigned long flags, unsigned long
* The caller must specify @start, @end, @flags, and @desc
* (which may be IORES_DESC_NONE).
*/
-static int find_next_iomem_res(resource_size_t start, resource_size_t end,
- unsigned long flags, unsigned long desc,
- struct resource *res)
+static int find_next_res(struct resource *parent, resource_size_t start,
+ resource_size_t end, unsigned long flags,
+ unsigned long desc, struct resource *res)
{
struct resource *p;
@@ -351,7 +352,7 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
read_lock(&resource_lock);
- for_each_resource(&iomem_resource, p, false) {
+ for_each_resource(parent, p, false) {
/* If we passed the resource we are looking for, stop */
if (p->start > end) {
p = NULL;
@@ -382,16 +383,23 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
return p ? 0 : -ENODEV;
}
-static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
- unsigned long flags, unsigned long desc,
- void *arg,
- int (*func)(struct resource *, void *))
+static int find_next_iomem_res(resource_size_t start, resource_size_t end,
+ unsigned long flags, unsigned long desc,
+ struct resource *res)
+{
+ return find_next_res(&iomem_resource, start, end, flags, desc, res);
+}
+
+static int walk_res_desc(struct resource *parent, resource_size_t start,
+ resource_size_t end, unsigned long flags,
+ unsigned long desc, void *arg,
+ int (*func)(struct resource *, void *))
{
struct resource res;
int ret = -EINVAL;
while (start < end &&
- !find_next_iomem_res(start, end, flags, desc, &res)) {
+ !find_next_res(parent, start, end, flags, desc, &res)) {
ret = (*func)(&res, arg);
if (ret)
break;
@@ -402,6 +410,15 @@ static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
return ret;
}
+static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
+ unsigned long flags, unsigned long desc,
+ void *arg,
+ int (*func)(struct resource *, void *))
+{
+ return walk_res_desc(&iomem_resource, start, end, flags, desc, arg, func);
+}
+
+
/**
* walk_iomem_res_desc - Walks through iomem resources and calls func()
* with matching resource ranges.
@@ -426,6 +443,26 @@ int walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start,
}
EXPORT_SYMBOL_GPL(walk_iomem_res_desc);
+#ifdef CONFIG_EFI_SOFT_RESERVE
+struct resource soft_reserve_resource = {
+ .name = "Soft Reserved",
+ .start = 0,
+ .end = -1,
+ .desc = IORES_DESC_SOFT_RESERVED,
+ .flags = IORESOURCE_MEM,
+};
+EXPORT_SYMBOL_GPL(soft_reserve_resource);
+
+int walk_soft_reserve_res_desc(unsigned long desc, unsigned long flags,
+ u64 start, u64 end, void *arg,
+ int (*func)(struct resource *, void *))
+{
+ return walk_res_desc(&soft_reserve_resource, start, end, flags, desc,
+ arg, func);
+}
+EXPORT_SYMBOL_GPL(walk_soft_reserve_res_desc);
+#endif
+
/*
* This function calls the @func callback against all memory ranges of type
* System RAM which are marked as IORESOURCE_SYSTEM_RAM and IORESOUCE_BUSY.
@@ -648,6 +685,22 @@ int region_intersects(resource_size_t start, size_t size, unsigned long flags,
}
EXPORT_SYMBOL_GPL(region_intersects);
+#ifdef CONFIG_EFI_SOFT_RESERVE
+int region_intersects_soft_reserve(resource_size_t start, size_t size,
+ unsigned long flags, unsigned long desc)
+{
+ int ret;
+
+ read_lock(&resource_lock);
+ ret = __region_intersects(&soft_reserve_resource, start, size, flags,
+ desc);
+ read_unlock(&resource_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(region_intersects_soft_reserve);
+#endif
+
void __weak arch_remove_reservations(struct resource *avail)
{
}
@@ -966,7 +1019,7 @@ EXPORT_SYMBOL_GPL(insert_resource);
* Insert a resource into the resource tree, possibly expanding it in order
* to make it encompass any conflicting resources.
*/
-void insert_resource_expand_to_fit(struct resource *root, struct resource *new)
+void __insert_resource_expand_to_fit(struct resource *root, struct resource *new)
{
if (new->parent)
return;
@@ -997,7 +1050,20 @@ void insert_resource_expand_to_fit(struct resource *root, struct resource *new)
* to use this interface. The former are built-in and only the latter,
* CXL, is a module.
*/
-EXPORT_SYMBOL_NS_GPL(insert_resource_expand_to_fit, "CXL");
+EXPORT_SYMBOL_NS_GPL(__insert_resource_expand_to_fit, "CXL");
+
+void insert_resource_expand_to_fit(struct resource *new)
+{
+ struct resource *root = &iomem_resource;
+
+#ifdef CONFIG_EFI_SOFT_RESERVE
+ if (new->desc == IORES_DESC_SOFT_RESERVED)
+ root = &soft_reserve_resource;
+#endif
+
+ __insert_resource_expand_to_fit(root, new);
+}
+EXPORT_SYMBOL_GPL(insert_resource_expand_to_fit);
/**
* remove_resource - Remove a resource in the resource tree
--
2.17.1On Thu, 20 Nov 2025 03:19:17 +0000
Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com> wrote:
> From: Dan Williams <dan.j.williams@intel.com>
>
> Insert Soft Reserved memory into a dedicated soft_reserve_resource tree
> instead of the iomem_resource tree at boot. Delay publishing these ranges
> into the iomem hierarchy until ownership is resolved and the HMEM path
> is ready to consume them.
>
> Publishing Soft Reserved ranges into iomem too early conflicts with CXL
> hotplug and prevents region assembly when those ranges overlap CXL
> windows.
>
> Follow up patches will reinsert Soft Reserved ranges into iomem after CXL
> window publication is complete and HMEM is ready to claim the memory. This
> provides a cleaner handoff between EFI-defined memory ranges and CXL
> resource management without trimming or deleting resources later.
>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
A couple of general comments below. I don't feel particularly strongly
about any of them however if you disagree! (other than the ever important
number of blank lines!) :)
Jonathan
> diff --git a/drivers/dax/hmem/device.c b/drivers/dax/hmem/device.c
> index f9e1a76a04a9..22732b729017 100644
> --- a/drivers/dax/hmem/device.c
> +++ b/drivers/dax/hmem/device.c
> @@ -83,8 +83,8 @@ static __init int hmem_register_one(struct resource *res, void *data)
>
> static __init int hmem_init(void)
> {
> - walk_iomem_res_desc(IORES_DESC_SOFT_RESERVED,
> - IORESOURCE_MEM, 0, -1, NULL, hmem_register_one);
> + walk_soft_reserve_res_desc(IORES_DESC_SOFT_RESERVED, IORESOURCE_MEM, 0,
Similar to below. If we are only putting MEM of type SOFT_RESERVED in here
can we drop those two as parameters?
> + -1, NULL, hmem_register_one);
> return 0;
> }
>
> diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
> index c18451a37e4f..48f4642f4bb8 100644
> --- a/drivers/dax/hmem/hmem.c
> +++ b/drivers/dax/hmem/hmem.c
> @@ -73,11 +73,14 @@ static int hmem_register_device(struct device *host, int target_nid,
> return 0;
> }
>
> - rc = region_intersects(res->start, resource_size(res), IORESOURCE_MEM,
> - IORES_DESC_SOFT_RESERVED);
> + rc = region_intersects_soft_reserve(res->start, resource_size(res),
> + IORESOURCE_MEM,
> + IORES_DESC_SOFT_RESERVED);
The flags seem perhaps redundant. Trade off between matching the more complex
existing functions and simplfying this. Maybe push them down into the
call and just have
rc = region_intersects_soft_reserved(res->start, resource_size(res));
here?
> if (rc != REGION_INTERSECTS)
> return 0;
>
> + /* TODO: Add Soft-Reserved memory back to iomem */
> +
> id = memregion_alloc(GFP_KERNEL);
> if (id < 0) {
> dev_err(host, "memregion allocation failure for %pr\n", res);
> diff --git a/kernel/resource.c b/kernel/resource.c
> index b9fa2a4ce089..208eaafcc681 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -402,6 +410,15 @@ static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
> return ret;
> }
>
> +static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
> + unsigned long flags, unsigned long desc,
> + void *arg,
> + int (*func)(struct resource *, void *))
> +{
> + return walk_res_desc(&iomem_resource, start, end, flags, desc, arg, func);
> +}
> +
Local style seems to be single line breaks - stick to that unless I'm missing
some reason this one is special.
> +
> /**
> /*
> * This function calls the @func callback against all memory ranges of type
> * System RAM which are marked as IORESOURCE_SYSTEM_RAM and IORESOUCE_BUSY.
> @@ -648,6 +685,22 @@ int region_intersects(resource_size_t start, size_t size, unsigned long flags,
> }
> EXPORT_SYMBOL_GPL(region_intersects);
>
> +#ifdef CONFIG_EFI_SOFT_RESERVE
> +int region_intersects_soft_reserve(resource_size_t start, size_t size,
> + unsigned long flags, unsigned long desc)
> +{
> + int ret;
> +
> + read_lock(&resource_lock);
> + ret = __region_intersects(&soft_reserve_resource, start, size, flags,
> + desc);
> + read_unlock(&resource_lock);
> +
> + return ret;
Perhaps the shortening of code makes it worth implementing this as:
guard(read_lock)(&resource_lock);
return __region_intersects();
Or ignore that until someone feels like a more general use of that
infrastructure in this file. Looks like there are a bunch of places
where I'd argue it is worth doing.
Jonathan
> +}
> +EXPORT_SYMBOL_GPL(region_intersects_soft_reserve);
> +#endif
On 11/19/25 8:19 PM, Smita Koralahalli wrote:
> From: Dan Williams <dan.j.williams@intel.com>
>
> Insert Soft Reserved memory into a dedicated soft_reserve_resource tree
> instead of the iomem_resource tree at boot. Delay publishing these ranges
> into the iomem hierarchy until ownership is resolved and the HMEM path
> is ready to consume them.
>
> Publishing Soft Reserved ranges into iomem too early conflicts with CXL
> hotplug and prevents region assembly when those ranges overlap CXL
> windows.
>
> Follow up patches will reinsert Soft Reserved ranges into iomem after CXL
> window publication is complete and HMEM is ready to claim the memory. This
> provides a cleaner handoff between EFI-defined memory ranges and CXL
> resource management without trimming or deleting resources later.
>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
With changes requested from Dan,
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> ---
> arch/x86/kernel/e820.c | 2 +-
> drivers/cxl/acpi.c | 2 +-
> drivers/dax/hmem/device.c | 4 +-
> drivers/dax/hmem/hmem.c | 7 ++-
> include/linux/ioport.h | 13 +++++-
> kernel/resource.c | 92 +++++++++++++++++++++++++++++++++------
> 6 files changed, 100 insertions(+), 20 deletions(-)
>
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index c3acbd26408b..c32f144f0e4a 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -1153,7 +1153,7 @@ void __init e820__reserve_resources_late(void)
> res = e820_res;
> for (i = 0; i < e820_table->nr_entries; i++) {
> if (!res->parent && res->end)
> - insert_resource_expand_to_fit(&iomem_resource, res);
> + insert_resource_expand_to_fit(res);
> res++;
> }
>
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index bd2e282ca93a..b37858f797be 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -847,7 +847,7 @@ static int add_cxl_resources(struct resource *cxl_res)
> */
> cxl_set_public_resource(res, new);
>
> - insert_resource_expand_to_fit(&iomem_resource, new);
> + __insert_resource_expand_to_fit(&iomem_resource, new);
>
> next = res->sibling;
> while (next && resource_overlaps(new, next)) {
> diff --git a/drivers/dax/hmem/device.c b/drivers/dax/hmem/device.c
> index f9e1a76a04a9..22732b729017 100644
> --- a/drivers/dax/hmem/device.c
> +++ b/drivers/dax/hmem/device.c
> @@ -83,8 +83,8 @@ static __init int hmem_register_one(struct resource *res, void *data)
>
> static __init int hmem_init(void)
> {
> - walk_iomem_res_desc(IORES_DESC_SOFT_RESERVED,
> - IORESOURCE_MEM, 0, -1, NULL, hmem_register_one);
> + walk_soft_reserve_res_desc(IORES_DESC_SOFT_RESERVED, IORESOURCE_MEM, 0,
> + -1, NULL, hmem_register_one);
> return 0;
> }
>
> diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
> index c18451a37e4f..48f4642f4bb8 100644
> --- a/drivers/dax/hmem/hmem.c
> +++ b/drivers/dax/hmem/hmem.c
> @@ -73,11 +73,14 @@ static int hmem_register_device(struct device *host, int target_nid,
> return 0;
> }
>
> - rc = region_intersects(res->start, resource_size(res), IORESOURCE_MEM,
> - IORES_DESC_SOFT_RESERVED);
> + rc = region_intersects_soft_reserve(res->start, resource_size(res),
> + IORESOURCE_MEM,
> + IORES_DESC_SOFT_RESERVED);
> if (rc != REGION_INTERSECTS)
> return 0;
>
> + /* TODO: Add Soft-Reserved memory back to iomem */
> +
> id = memregion_alloc(GFP_KERNEL);
> if (id < 0) {
> dev_err(host, "memregion allocation failure for %pr\n", res);
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index e8b2d6aa4013..e20226870a81 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -232,6 +232,9 @@ struct resource_constraint {
> /* PC/ISA/whatever - the normal PC address spaces: IO and memory */
> extern struct resource ioport_resource;
> extern struct resource iomem_resource;
> +#ifdef CONFIG_EFI_SOFT_RESERVE
> +extern struct resource soft_reserve_resource;
> +#endif
>
> extern struct resource *request_resource_conflict(struct resource *root, struct resource *new);
> extern int request_resource(struct resource *root, struct resource *new);
> @@ -242,7 +245,8 @@ extern void reserve_region_with_split(struct resource *root,
> const char *name);
> extern struct resource *insert_resource_conflict(struct resource *parent, struct resource *new);
> extern int insert_resource(struct resource *parent, struct resource *new);
> -extern void insert_resource_expand_to_fit(struct resource *root, struct resource *new);
> +extern void __insert_resource_expand_to_fit(struct resource *root, struct resource *new);
> +extern void insert_resource_expand_to_fit(struct resource *new);
> extern int remove_resource(struct resource *old);
> extern void arch_remove_reservations(struct resource *avail);
> extern int allocate_resource(struct resource *root, struct resource *new,
> @@ -409,6 +413,13 @@ walk_system_ram_res_rev(u64 start, u64 end, void *arg,
> extern int
> walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start, u64 end,
> void *arg, int (*func)(struct resource *, void *));
> +extern int
> +walk_soft_reserve_res_desc(unsigned long desc, unsigned long flags,
> + u64 start, u64 end, void *arg,
> + int (*func)(struct resource *, void *));
> +extern int
> +region_intersects_soft_reserve(resource_size_t start, size_t size,
> + unsigned long flags, unsigned long desc);
>
> struct resource *devm_request_free_mem_region(struct device *dev,
> struct resource *base, unsigned long size);
> diff --git a/kernel/resource.c b/kernel/resource.c
> index b9fa2a4ce089..208eaafcc681 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -321,13 +321,14 @@ static bool is_type_match(struct resource *p, unsigned long flags, unsigned long
> }
>
> /**
> - * find_next_iomem_res - Finds the lowest iomem resource that covers part of
> - * [@start..@end].
> + * find_next_res - Finds the lowest resource that covers part of
> + * [@start..@end].
> *
> * If a resource is found, returns 0 and @*res is overwritten with the part
> * of the resource that's within [@start..@end]; if none is found, returns
> * -ENODEV. Returns -EINVAL for invalid parameters.
> *
> + * @parent: resource tree root to search
> * @start: start address of the resource searched for
> * @end: end address of same resource
> * @flags: flags which the resource must have
> @@ -337,9 +338,9 @@ static bool is_type_match(struct resource *p, unsigned long flags, unsigned long
> * The caller must specify @start, @end, @flags, and @desc
> * (which may be IORES_DESC_NONE).
> */
> -static int find_next_iomem_res(resource_size_t start, resource_size_t end,
> - unsigned long flags, unsigned long desc,
> - struct resource *res)
> +static int find_next_res(struct resource *parent, resource_size_t start,
> + resource_size_t end, unsigned long flags,
> + unsigned long desc, struct resource *res)
> {
> struct resource *p;
>
> @@ -351,7 +352,7 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
>
> read_lock(&resource_lock);
>
> - for_each_resource(&iomem_resource, p, false) {
> + for_each_resource(parent, p, false) {
> /* If we passed the resource we are looking for, stop */
> if (p->start > end) {
> p = NULL;
> @@ -382,16 +383,23 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
> return p ? 0 : -ENODEV;
> }
>
> -static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
> - unsigned long flags, unsigned long desc,
> - void *arg,
> - int (*func)(struct resource *, void *))
> +static int find_next_iomem_res(resource_size_t start, resource_size_t end,
> + unsigned long flags, unsigned long desc,
> + struct resource *res)
> +{
> + return find_next_res(&iomem_resource, start, end, flags, desc, res);
> +}
> +
> +static int walk_res_desc(struct resource *parent, resource_size_t start,
> + resource_size_t end, unsigned long flags,
> + unsigned long desc, void *arg,
> + int (*func)(struct resource *, void *))
> {
> struct resource res;
> int ret = -EINVAL;
>
> while (start < end &&
> - !find_next_iomem_res(start, end, flags, desc, &res)) {
> + !find_next_res(parent, start, end, flags, desc, &res)) {
> ret = (*func)(&res, arg);
> if (ret)
> break;
> @@ -402,6 +410,15 @@ static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
> return ret;
> }
>
> +static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
> + unsigned long flags, unsigned long desc,
> + void *arg,
> + int (*func)(struct resource *, void *))
> +{
> + return walk_res_desc(&iomem_resource, start, end, flags, desc, arg, func);
> +}
> +
> +
> /**
> * walk_iomem_res_desc - Walks through iomem resources and calls func()
> * with matching resource ranges.
> @@ -426,6 +443,26 @@ int walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start,
> }
> EXPORT_SYMBOL_GPL(walk_iomem_res_desc);
>
> +#ifdef CONFIG_EFI_SOFT_RESERVE
> +struct resource soft_reserve_resource = {
> + .name = "Soft Reserved",
> + .start = 0,
> + .end = -1,
> + .desc = IORES_DESC_SOFT_RESERVED,
> + .flags = IORESOURCE_MEM,
> +};
> +EXPORT_SYMBOL_GPL(soft_reserve_resource);
> +
> +int walk_soft_reserve_res_desc(unsigned long desc, unsigned long flags,
> + u64 start, u64 end, void *arg,
> + int (*func)(struct resource *, void *))
> +{
> + return walk_res_desc(&soft_reserve_resource, start, end, flags, desc,
> + arg, func);
> +}
> +EXPORT_SYMBOL_GPL(walk_soft_reserve_res_desc);
> +#endif
> +
> /*
> * This function calls the @func callback against all memory ranges of type
> * System RAM which are marked as IORESOURCE_SYSTEM_RAM and IORESOUCE_BUSY.
> @@ -648,6 +685,22 @@ int region_intersects(resource_size_t start, size_t size, unsigned long flags,
> }
> EXPORT_SYMBOL_GPL(region_intersects);
>
> +#ifdef CONFIG_EFI_SOFT_RESERVE
> +int region_intersects_soft_reserve(resource_size_t start, size_t size,
> + unsigned long flags, unsigned long desc)
> +{
> + int ret;
> +
> + read_lock(&resource_lock);
> + ret = __region_intersects(&soft_reserve_resource, start, size, flags,
> + desc);
> + read_unlock(&resource_lock);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(region_intersects_soft_reserve);
> +#endif
> +
> void __weak arch_remove_reservations(struct resource *avail)
> {
> }
> @@ -966,7 +1019,7 @@ EXPORT_SYMBOL_GPL(insert_resource);
> * Insert a resource into the resource tree, possibly expanding it in order
> * to make it encompass any conflicting resources.
> */
> -void insert_resource_expand_to_fit(struct resource *root, struct resource *new)
> +void __insert_resource_expand_to_fit(struct resource *root, struct resource *new)
> {
> if (new->parent)
> return;
> @@ -997,7 +1050,20 @@ void insert_resource_expand_to_fit(struct resource *root, struct resource *new)
> * to use this interface. The former are built-in and only the latter,
> * CXL, is a module.
> */
> -EXPORT_SYMBOL_NS_GPL(insert_resource_expand_to_fit, "CXL");
> +EXPORT_SYMBOL_NS_GPL(__insert_resource_expand_to_fit, "CXL");
> +
> +void insert_resource_expand_to_fit(struct resource *new)
> +{
> + struct resource *root = &iomem_resource;
> +
> +#ifdef CONFIG_EFI_SOFT_RESERVE
> + if (new->desc == IORES_DESC_SOFT_RESERVED)
> + root = &soft_reserve_resource;
> +#endif
> +
> + __insert_resource_expand_to_fit(root, new);
> +}
> +EXPORT_SYMBOL_GPL(insert_resource_expand_to_fit);
>
> /**
> * remove_resource - Remove a resource in the resource tree
Smita Koralahalli wrote:
> From: Dan Williams <dan.j.williams@intel.com>
>
> Insert Soft Reserved memory into a dedicated soft_reserve_resource tree
> instead of the iomem_resource tree at boot. Delay publishing these ranges
> into the iomem hierarchy until ownership is resolved and the HMEM path
> is ready to consume them.
>
> Publishing Soft Reserved ranges into iomem too early conflicts with CXL
> hotplug and prevents region assembly when those ranges overlap CXL
> windows.
>
> Follow up patches will reinsert Soft Reserved ranges into iomem after CXL
> window publication is complete and HMEM is ready to claim the memory. This
> provides a cleaner handoff between EFI-defined memory ranges and CXL
> resource management without trimming or deleting resources later.
Please, when you modify a patch from an original, add your
Co-developed-by: and clarify what you changed.
>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
> ---
> arch/x86/kernel/e820.c | 2 +-
> drivers/cxl/acpi.c | 2 +-
> drivers/dax/hmem/device.c | 4 +-
> drivers/dax/hmem/hmem.c | 7 ++-
> include/linux/ioport.h | 13 +++++-
> kernel/resource.c | 92 +++++++++++++++++++++++++++++++++------
> 6 files changed, 100 insertions(+), 20 deletions(-)
>
[..]
> @@ -426,6 +443,26 @@ int walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start,
> }
> EXPORT_SYMBOL_GPL(walk_iomem_res_desc);
>
> +#ifdef CONFIG_EFI_SOFT_RESERVE
> +struct resource soft_reserve_resource = {
> + .name = "Soft Reserved",
> + .start = 0,
> + .end = -1,
> + .desc = IORES_DESC_SOFT_RESERVED,
> + .flags = IORESOURCE_MEM,
> +};
> +EXPORT_SYMBOL_GPL(soft_reserve_resource);
It looks like one of the things you changed from my RFC was the addition
of walk_soft_reserve_res_desc() and region_intersects_soft_reserve().
With those APIs not only does this symbol not need to be exported, but
it also can be static / private to resource.c.
> +
> +int walk_soft_reserve_res_desc(unsigned long desc, unsigned long flags,
> + u64 start, u64 end, void *arg,
> + int (*func)(struct resource *, void *))
> +{
> + return walk_res_desc(&soft_reserve_resource, start, end, flags, desc,
> + arg, func);
> +}
> +EXPORT_SYMBOL_GPL(walk_soft_reserve_res_desc);
> +#endif
> +
> /*
> * This function calls the @func callback against all memory ranges of type
> * System RAM which are marked as IORESOURCE_SYSTEM_RAM and IORESOUCE_BUSY.
> @@ -648,6 +685,22 @@ int region_intersects(resource_size_t start, size_t size, unsigned long flags,
> }
> EXPORT_SYMBOL_GPL(region_intersects);
>
> +#ifdef CONFIG_EFI_SOFT_RESERVE
> +int region_intersects_soft_reserve(resource_size_t start, size_t size,
> + unsigned long flags, unsigned long desc)
> +{
> + int ret;
> +
> + read_lock(&resource_lock);
> + ret = __region_intersects(&soft_reserve_resource, start, size, flags,
> + desc);
> + read_unlock(&resource_lock);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(region_intersects_soft_reserve);
> +#endif
> +
> void __weak arch_remove_reservations(struct resource *avail)
> {
> }
> @@ -966,7 +1019,7 @@ EXPORT_SYMBOL_GPL(insert_resource);
> * Insert a resource into the resource tree, possibly expanding it in order
> * to make it encompass any conflicting resources.
> */
> -void insert_resource_expand_to_fit(struct resource *root, struct resource *new)
> +void __insert_resource_expand_to_fit(struct resource *root, struct resource *new)
> {
> if (new->parent)
> return;
> @@ -997,7 +1050,20 @@ void insert_resource_expand_to_fit(struct resource *root, struct resource *new)
> * to use this interface. The former are built-in and only the latter,
> * CXL, is a module.
> */
> -EXPORT_SYMBOL_NS_GPL(insert_resource_expand_to_fit, "CXL");
> +EXPORT_SYMBOL_NS_GPL(__insert_resource_expand_to_fit, "CXL");
> +
> +void insert_resource_expand_to_fit(struct resource *new)
> +{
> + struct resource *root = &iomem_resource;
> +
> +#ifdef CONFIG_EFI_SOFT_RESERVE
> + if (new->desc == IORES_DESC_SOFT_RESERVED)
> + root = &soft_reserve_resource;
> +#endif
I can not say I am entirely happy with this change, I would prefer to
avoid ifdef in C, and I would prefer not to break the legacy semantics
of this function, but it meets the spirit of the original RFC without
introducing a new insert_resource_late(). I assume review feedback
requested this?
> + __insert_resource_expand_to_fit(root, new);
> +}
> +EXPORT_SYMBOL_GPL(insert_resource_expand_to_fit);
There are no consumers for this export, so it can be dropped.
Hi,
Sorry for the delay here. I was on vacation. Responses inline.
On 12/2/2025 2:19 PM, dan.j.williams@intel.com wrote:
> Smita Koralahalli wrote:
>> From: Dan Williams <dan.j.williams@intel.com>
>>
>> Insert Soft Reserved memory into a dedicated soft_reserve_resource tree
>> instead of the iomem_resource tree at boot. Delay publishing these ranges
>> into the iomem hierarchy until ownership is resolved and the HMEM path
>> is ready to consume them.
>>
>> Publishing Soft Reserved ranges into iomem too early conflicts with CXL
>> hotplug and prevents region assembly when those ranges overlap CXL
>> windows.
>>
>> Follow up patches will reinsert Soft Reserved ranges into iomem after CXL
>> window publication is complete and HMEM is ready to claim the memory. This
>> provides a cleaner handoff between EFI-defined memory ranges and CXL
>> resource management without trimming or deleting resources later.
>
> Please, when you modify a patch from an original, add your
> Co-developed-by: and clarify what you changed.
Thanks Dan. Yeah, this was a bit of a gray area for me. I had the
impression or remember reading somewhere that Co-developed-by tags are
typically added only when the modifications are substantial, so I didn’t
include it initially. I will add the Co-developed-by: line.
>
>>
>> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
>> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
>> ---
>> arch/x86/kernel/e820.c | 2 +-
>> drivers/cxl/acpi.c | 2 +-
>> drivers/dax/hmem/device.c | 4 +-
>> drivers/dax/hmem/hmem.c | 7 ++-
>> include/linux/ioport.h | 13 +++++-
>> kernel/resource.c | 92 +++++++++++++++++++++++++++++++++------
>> 6 files changed, 100 insertions(+), 20 deletions(-)
>>
> [..]
>> @@ -426,6 +443,26 @@ int walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start,
>> }
>> EXPORT_SYMBOL_GPL(walk_iomem_res_desc);
>>
>> +#ifdef CONFIG_EFI_SOFT_RESERVE
>> +struct resource soft_reserve_resource = {
>> + .name = "Soft Reserved",
>> + .start = 0,
>> + .end = -1,
>> + .desc = IORES_DESC_SOFT_RESERVED,
>> + .flags = IORESOURCE_MEM,
>> +};
>> +EXPORT_SYMBOL_GPL(soft_reserve_resource);
>
> It looks like one of the things you changed from my RFC was the addition
> of walk_soft_reserve_res_desc() and region_intersects_soft_reserve().
> With those APIs not only does this symbol not need to be exported, but
> it also can be static / private to resource.c.
I remember these helpers were introduced in your RFC but I think they
weren't yet defined. With them in place, agreed there’s no need to
export soft_reserve_resource. Will fix this in the next revision.
>
>> +
>> +int walk_soft_reserve_res_desc(unsigned long desc, unsigned long flags,
>> + u64 start, u64 end, void *arg,
>> + int (*func)(struct resource *, void *))
>> +{
>> + return walk_res_desc(&soft_reserve_resource, start, end, flags, desc,
>> + arg, func);
>> +}
>> +EXPORT_SYMBOL_GPL(walk_soft_reserve_res_desc);
>> +#endif
>> +
>> /*
>> * This function calls the @func callback against all memory ranges of type
>> * System RAM which are marked as IORESOURCE_SYSTEM_RAM and IORESOUCE_BUSY.
>> @@ -648,6 +685,22 @@ int region_intersects(resource_size_t start, size_t size, unsigned long flags,
>> }
>> EXPORT_SYMBOL_GPL(region_intersects);
>>
>> +#ifdef CONFIG_EFI_SOFT_RESERVE
>> +int region_intersects_soft_reserve(resource_size_t start, size_t size,
>> + unsigned long flags, unsigned long desc)
>> +{
>> + int ret;
>> +
>> + read_lock(&resource_lock);
>> + ret = __region_intersects(&soft_reserve_resource, start, size, flags,
>> + desc);
>> + read_unlock(&resource_lock);
>> +
>> + return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(region_intersects_soft_reserve);
>> +#endif
>> +
>> void __weak arch_remove_reservations(struct resource *avail)
>> {
>> }
>> @@ -966,7 +1019,7 @@ EXPORT_SYMBOL_GPL(insert_resource);
>> * Insert a resource into the resource tree, possibly expanding it in order
>> * to make it encompass any conflicting resources.
>> */
>> -void insert_resource_expand_to_fit(struct resource *root, struct resource *new)
>> +void __insert_resource_expand_to_fit(struct resource *root, struct resource *new)
>> {
>> if (new->parent)
>> return;
>> @@ -997,7 +1050,20 @@ void insert_resource_expand_to_fit(struct resource *root, struct resource *new)
>> * to use this interface. The former are built-in and only the latter,
>> * CXL, is a module.
>> */
>> -EXPORT_SYMBOL_NS_GPL(insert_resource_expand_to_fit, "CXL");
>> +EXPORT_SYMBOL_NS_GPL(__insert_resource_expand_to_fit, "CXL");
>> +
>> +void insert_resource_expand_to_fit(struct resource *new)
>> +{
>> + struct resource *root = &iomem_resource;
>> +
>> +#ifdef CONFIG_EFI_SOFT_RESERVE
>> + if (new->desc == IORES_DESC_SOFT_RESERVED)
>> + root = &soft_reserve_resource;
>> +#endif
>
> I can not say I am entirely happy with this change, I would prefer to
> avoid ifdef in C, and I would prefer not to break the legacy semantics
> of this function, but it meets the spirit of the original RFC without
> introducing a new insert_resource_late(). I assume review feedback
> requested this?
Yeah here,
https://lore.kernel.org/all/20250909161210.GBaMBR2rN8h6eT9JHe@fat_crate.local/
>
>> + __insert_resource_expand_to_fit(root, new);
>> +}
>> +EXPORT_SYMBOL_GPL(insert_resource_expand_to_fit);
>
> There are no consumers for this export, so it can be dropped.
Okay.
Thanks
Smita
Koralahalli Channabasappa, Smita wrote:
> Hi,
>
> Sorry for the delay here. I was on vacation. Responses inline.
>
> On 12/2/2025 2:19 PM, dan.j.williams@intel.com wrote:
> > Smita Koralahalli wrote:
> >> From: Dan Williams <dan.j.williams@intel.com>
> >>
> >> Insert Soft Reserved memory into a dedicated soft_reserve_resource tree
> >> instead of the iomem_resource tree at boot. Delay publishing these ranges
> >> into the iomem hierarchy until ownership is resolved and the HMEM path
> >> is ready to consume them.
> >>
> >> Publishing Soft Reserved ranges into iomem too early conflicts with CXL
> >> hotplug and prevents region assembly when those ranges overlap CXL
> >> windows.
> >>
> >> Follow up patches will reinsert Soft Reserved ranges into iomem after CXL
> >> window publication is complete and HMEM is ready to claim the memory. This
> >> provides a cleaner handoff between EFI-defined memory ranges and CXL
> >> resource management without trimming or deleting resources later.
> >
> > Please, when you modify a patch from an original, add your
> > Co-developed-by: and clarify what you changed.
>
> Thanks Dan. Yeah, this was a bit of a gray area for me. I had the
> impression or remember reading somewhere that Co-developed-by tags are
> typically added only when the modifications are substantial, so I didn’t
> include it initially. I will add the Co-developed-by: line.
Yes, there are no hard and fast rules here. My expectation is that if
you make any changes to a patch that change its "git patch-id" result,
then add Co-developed-by. If you make "substantial" modifcations then
consider taking Authorship and move the original Author to
Co-developed-by.
[..]
> >> +void insert_resource_expand_to_fit(struct resource *new)
> >> +{
> >> + struct resource *root = &iomem_resource;
> >> +
> >> +#ifdef CONFIG_EFI_SOFT_RESERVE
> >> + if (new->desc == IORES_DESC_SOFT_RESERVED)
> >> + root = &soft_reserve_resource;
> >> +#endif
> >
> > I can not say I am entirely happy with this change, I would prefer to
> > avoid ifdef in C, and I would prefer not to break the legacy semantics
> > of this function, but it meets the spirit of the original RFC without
> > introducing a new insert_resource_late(). I assume review feedback
> > requested this?
>
> Yeah here,
> https://lore.kernel.org/all/20250909161210.GBaMBR2rN8h6eT9JHe@fat_crate.local/
Thanks, I will go reply there.
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