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Message-ID: <537527fe-55be-4661-a0c6-ba9fe344bc35@fujitsu.com>
Date: Mon, 1 Sep 2025 02:59:31 +0000
From: "Zhijian Li (Fujitsu)" <lizhijian@...itsu.com>
To: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>,
"linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"nvdimm@...ts.linux.dev" <nvdimm@...ts.linux.dev>,
"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
CC: Davidlohr Bueso <dave@...olabs.net>, Jonathan Cameron
<jonathan.cameron@...wei.com>, Dave Jiang <dave.jiang@...el.com>, Alison
Schofield <alison.schofield@...el.com>, Vishal Verma
<vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, Dan Williams
<dan.j.williams@...el.com>, Matthew Wilcox <willy@...radead.org>, Jan Kara
<jack@...e.cz>, "Rafael J . Wysocki" <rafael@...nel.org>, Len Brown
<len.brown@...el.com>, Pavel Machek <pavel@...nel.org>, Li Ming
<ming.li@...omail.com>, Jeff Johnson <jeff.johnson@....qualcomm.com>, Ying
Huang <huang.ying.caritas@...il.com>, "Xingtao Yao (Fujitsu)"
<yaoxt.fnst@...itsu.com>, Peter Zijlstra <peterz@...radead.org>, Greg KH
<gregkh@...uxfoundation.org>, Nathan Fontenot <nathan.fontenot@....com>,
Terry Bowman <terry.bowman@....com>, Robert Richter <rrichter@....com>,
Benjamin Cheatham <benjamin.cheatham@....com>, PradeepVineshReddy Kodamati
<PradeepVineshReddy.Kodamati@....com>
Subject: Re: [PATCH 1/6] dax/hmem, e820, resource: Defer Soft Reserved
registration until hmem is ready
On 22/08/2025 11:41, Smita Koralahalli wrote:
> Insert Soft Reserved memory into a dedicated soft_reserve_resource tree
> instead of the iomem_resource tree at boot.
>
> Publishing Soft Reserved ranges into iomem too early causes conflicts with
> CXL hotplug and region assembly failure, especially when Soft Reserved
> overlaps CXL regions.
>
> Re-inserting these ranges into iomem will be handled in follow-up patches,
> after ensuring CXL window publication ordering is stabilized and when the
> dax_hmem is ready to consume them.
>
> This avoids trimming or deleting resources later and provides a cleaner
> handoff between EFI-defined memory and CXL resource management.
>
> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
> arch/x86/kernel/e820.c | 2 +-
> drivers/dax/hmem/device.c | 4 +--
> drivers/dax/hmem/hmem.c | 8 +++++
> include/linux/ioport.h | 24 +++++++++++++
> kernel/resource.c | 73 +++++++++++++++++++++++++++++++++------
> 5 files changed, 97 insertions(+), 14 deletions(-)
>
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index c3acbd26408b..aef1ff2cabda 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_late(res);
> res++;
> }
>
> 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..d5b8f06d531e 100644
> --- a/drivers/dax/hmem/hmem.c
> +++ b/drivers/dax/hmem/hmem.c
> @@ -73,10 +73,18 @@ static int hmem_register_device(struct device *host, int target_nid,
> return 0;
> }
>
> +#ifdef CONFIG_EFI_SOFT_RESERVE
Note that dax_kmem currently depends on CONFIG_EFI_SOFT_RESERVED, so this conditional check may be redundant.
> + rc = region_intersects_soft_reserve(res->start, resource_size(res),
> + IORESOURCE_MEM,
> + IORES_DESC_SOFT_RESERVED);
> + if (rc != REGION_INTERSECTS)
> + return 0;
> +#else
> rc = region_intersects(res->start, resource_size(res), IORESOURCE_MEM,
> IORES_DESC_SOFT_RESERVED);
> if (rc != REGION_INTERSECTS)
> return 0;
> +#endif
>
Additionally, please add a TODO note here (e.g., "Add soft-reserved memory back to iomem").
> id = memregion_alloc(GFP_KERNEL);
> if (id < 0) {
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index e8b2d6aa4013..889bc4982777 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);
> @@ -255,6 +258,22 @@ int adjust_resource(struct resource *res, resource_size_t start,
> resource_size_t size);
> resource_size_t resource_alignment(struct resource *res);
>
> +
> +#ifdef CONFIG_EFI_SOFT_RESERVE
> +static inline void insert_resource_late(struct resource *new)
> +{
> + if (new->desc == IORES_DESC_SOFT_RESERVED)
> + insert_resource_expand_to_fit(&soft_reserve_resource, new);
> + else
> + insert_resource_expand_to_fit(&iomem_resource, new);
> +}
> +#else
> +static inline void insert_resource_late(struct resource *new)
> +{
> + insert_resource_expand_to_fit(&iomem_resource, new);
> +}
> +#endif
> +
> /**
> * resource_set_size - Calculate resource end address from size and start
> * @res: Resource descriptor
> @@ -409,6 +428,11 @@ 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 *));
> +int walk_soft_reserve_res_desc(unsigned long desc, unsigned long flags,
> + u64 start, u64 end, void *arg,
> + int (*func)(struct resource *, void *));
> +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 f9bb5481501a..8479a99441e2 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 +685,20 @@ int region_intersects(resource_size_t start, size_t size, unsigned long flags,
> }
> EXPORT_SYMBOL_GPL(region_intersects);
>
> +int region_intersects_soft_reserve(resource_size_t start, size_t size,
> + unsigned long flags, unsigned long desc)
Shouldn't this function be implemented uder `#if CONFIG_EFI_SOFT_RESERVE`? Otherwise it may cause compilation failures when the config is disabled.
Thanks
Zhijian
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