Re: [PATCH v2 1/4] kernel/resource: Introduce managed SOFT RESERVED resources

Fan Ni
2025-01-22T05:52:48Z

On Thu, Jan 16, 2025 at 11:42:05AM -0600, Nathan Fontenot wrote:
> Introduce the ability to manage SOFT RESERVED kernel resources prior to
> these resources being placed in the iomem resource tree. This provides
> the ability for drivers to update SOFT RESERVED resources that intersect
> with their memory resources.
>
> During boot, any resources marked as IORES_DESC_SOFT_RESERVED are placed
> on the soft reserve resource tree. Once boot completes all resources
> are placed on the iomem resource tree. This behavior is gated by a new
> kernel option CONFIG_SOFT_RESERVED_MANAGED.
>
> As part of this update two new interfaces are added for management of
> the SOFT RESERVED resources. The release_srmem_region_adjustable()
> routine allows for removing pieces of SOFT RESERVED resources. The
> the merge_srmem_resources() allows drivers to merge any remaining SOFT
> RESERVED resources into the iomem resource tree once updatea are complete.
>
> Signed-off-by: Nathan Fontenot <nathan.fontenot@amd.com>
> ---
> include/linux/ioport.h | 9 +++++
> kernel/resource.c | 79 +++++++++++++++++++++++++++++++++++++++---
> lib/Kconfig | 4 +++
> 3 files changed, 87 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 6e9fb667a1c5..2c95cf0be45e 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -249,6 +249,15 @@ struct resource *lookup_resource(struct resource *root, resource_size_t start);
> int adjust_resource(struct resource *res, resource_size_t start,
> resource_size_t size);
> resource_size_t resource_alignment(struct resource *res);
> +
> +#ifdef CONFIG_SOFT_RESERVED_MANAGED
> +void merge_srmem_resources(void);
> +extern void release_srmem_region_adjustable(resource_size_t start,
> + resource_size_t size);
> +#else
> +static inline void merge_srmem_resources(void) { }
> +#endif
> +
> static inline resource_size_t resource_size(const struct resource *res)
> {
> return res->end - res->start + 1;
> diff --git a/kernel/resource.c b/kernel/resource.c
> index a83040fde236..9db420078a3f 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -48,6 +48,14 @@ struct resource iomem_resource = {
> };
> EXPORT_SYMBOL(iomem_resource);
>
> +static struct resource srmem_resource = {
> + .name = "Soft Reserved mem",
> + .start = 0,
> + .end = -1,
> + .flags = IORESOURCE_MEM,
> + .desc = IORES_DESC_SOFT_RESERVED,
> +};
> +
> static DEFINE_RWLOCK(resource_lock);
>
> static struct resource *next_resource(struct resource *p, bool skip_children)
> @@ -818,6 +826,19 @@ static struct resource * __insert_resource(struct resource *parent, struct resou
> {
> struct resource *first, *next;
>
> + if (IS_ENABLED(CONFIG_SOFT_RESERVED_MANAGED)) {
> + /*
> + * During boot SOFT RESERVED resources are placed on the srmem
> + * resource tree. These resources may be updated later in boot,
> + * for example see the CXL driver, prior to being merged into
> + * the iomem resource tree.
> + */
> + if (system_state < SYSTEM_RUNNING &&
> + parent == &iomem_resource &&
> + new->desc == IORES_DESC_SOFT_RESERVED)
> + parent = &srmem_resource;
> + }
> +
> for (;; parent = first) {
> first = __request_resource(parent, new);
> if (!first)
> @@ -1336,11 +1357,12 @@ void __release_region(struct resource *parent, resource_size_t start,
> }
> EXPORT_SYMBOL(__release_region);
>
> -#ifdef CONFIG_MEMORY_HOTREMOVE

If CONFIG_MEMORY_HOTREMOVE not defined, it seems we do not have a
user for release_region_adjustable as
release_mem_region_adjustable() will not exist.

Fan
> /**
> - * release_mem_region_adjustable - release a previously reserved memory region
> + * release_region_adjustable - release a previously reserved memory region
> + * @parent: resource tree to release resource from
> * @start: resource start address
> * @size: resource region size
> + * @busy_check: check for IORESOURCE_BUSY
> *
> * This interface is intended for memory hot-delete. The requested region
> * is released from a currently busy memory resource. The requested region
> @@ -1356,9 +1378,11 @@ EXPORT_SYMBOL(__release_region);
> * assumes that all children remain in the lower address entry for
> * simplicity. Enhance this logic when necessary.
> */
> -void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
> +static void release_region_adjustable(struct resource *parent,
> + resource_size_t start,
> + resource_size_t size,
> + bool busy_check)
> {
> - struct resource *parent = &iomem_resource;
> struct resource *new_res = NULL;
> bool alloc_nofail = false;
> struct resource **p;
> @@ -1395,7 +1419,7 @@ void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
> if (!(res->flags & IORESOURCE_MEM))
> break;
>
> - if (!(res->flags & IORESOURCE_BUSY)) {
> + if (busy_check && !(res->flags & IORESOURCE_BUSY)) {
> p = &res->child;
> continue;
> }
> @@ -1445,6 +1469,51 @@ void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
> write_unlock(&resource_lock);
> free_resource(new_res);
> }
> +
> +#ifdef CONFIG_SOFT_RESERVED_MANAGED
> +/**
> + * merge_srmem_resources - merge srmem resources into the iomem resource tree
> + *
> + * This is intended to allow kernel drivers that manage the SOFT RESERVED
> + * resources to merge any remaining resources into the iomem resource tree
> + * once any updates have been made.
> + */
> +void merge_srmem_resources(void)
> +{
> + struct resource *res, *next;
> + int rc;
> +
> + for (res = srmem_resource.child; res; res = next) {
> + next = next_resource(res, true);
> +
> + write_lock(&resource_lock);
> +
> + if (WARN_ON(__release_resource(res, true))) {
> + write_unlock(&resource_lock);
> + continue;
> + }
> +
> + if (WARN_ON(__insert_resource(&iomem_resource, res)))
> + __insert_resource(&srmem_resource, res);
> +
> + write_unlock(&resource_lock);
> + }
> +}
> +EXPORT_SYMBOL_GPL(merge_srmem_resources);
> +
> +void release_srmem_region_adjustable(resource_size_t start,
> + resource_size_t size)
> +{
> + release_region_adjustable(&srmem_resource, start, size, false);
> +}
> +EXPORT_SYMBOL(release_srmem_region_adjustable);
> +#endif
> +
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
> +{
> + release_region_adjustable(&iomem_resource, start, size, true);
> +}
> #endif /* CONFIG_MEMORY_HOTREMOVE */
>
> #ifdef CONFIG_MEMORY_HOTPLUG
> diff --git a/lib/Kconfig b/lib/Kconfig
> index b38849af6f13..4f4011334051 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -777,3 +777,7 @@ config POLYNOMIAL
>
> config FIRMWARE_TABLE
> bool
> +
> +config SOFT_RESERVED_MANAGED
> + bool
> + default n
> --
> 2.43.0
>