[ add dri-devel and nouveau ]
Dan Williams wrote:
> The core of devm_request_free_mem_region() is a helper that searches for
> free space in iomem_resource and performs __request_region_locked() on
> the result of that search. The policy choices of the implementation
> conform to what CONFIG_DEVICE_PRIVATE users want which is memory that is
> immediately marked busy, and a preference to search for the first-fit
> free range in descending order from the top of the physical address
> space.
>
> CXL has a need for a similar allocator, but with the following tweaks:
>
> 1/ Search for free space in ascending order
>
> 2/ Search for free space relative to a given CXL window
>
> 3/ 'insert' rather than 'request' the new resource given downstream
> drivers from the CXL Region driver (like the pmem or dax drivers) are
> responsible for request_mem_region() when they activate the memory
> range.
>
> Rework __request_free_mem_region() into get_free_mem_region() which
> takes a set of GFR_* (Get Free Region) flags to control the allocation
> policy (ascending vs descending), and "busy" policy (insert_resource()
> vs request_region()).
>
> As part of the consolidation of the legacy GFR_REQUEST_REGION case with
> the new default of just inserting a new resource into the free space
> some minor cleanups like not checking for NULL before calling
> devres_free() (which does its own check) is included.
>
> Suggested-by: Jason Gunthorpe <j...@nvidia.com>
> Link: https://lore.kernel.org/linux-cxl/20220420143406.gy2120...@nvidia.com/
> Cc: Matthew Wilcox <wi...@infradead.org>
> Cc: Christoph Hellwig <h...@lst.de>
Jason, Christoph, anyone else that depends on CONFIG_DEVICE_PRIVATE,
Just a heads up that with Jonathan's review I am going to proceed with
pushing this change to linux-next. Please holler if
CONFIG_DEVICE_PRIVATE starts misbehaving, or if you have other feedback,
and I will get it fixed up.
> Signed-off-by: Dan Williams <dan.j.willi...@intel.com>
> ---
> include/linux/ioport.h | 2 +
> kernel/resource.c | 178
> +++++++++++++++++++++++++++++++++++++++---------
> mm/Kconfig | 5 +
> 3 files changed, 150 insertions(+), 35 deletions(-)
>
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 79d1ad6d6275..616b683563a9 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -330,6 +330,8 @@ struct resource *devm_request_free_mem_region(struct
> device *dev,
> struct resource *base, unsigned long size);
> struct resource *request_free_mem_region(struct resource *base,
> unsigned long size, const char *name);
> +struct resource *alloc_free_mem_region(struct resource *base,
> + unsigned long size, unsigned long align, const char *name);
>
> static inline void irqresource_disabled(struct resource *res, u32 irq)
> {
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 53a534db350e..4c5e80b92f2f 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -489,8 +489,9 @@ int __weak page_is_ram(unsigned long pfn)
> }
> EXPORT_SYMBOL_GPL(page_is_ram);
>
> -static int __region_intersects(resource_size_t start, size_t size,
> - unsigned long flags, unsigned long desc)
> +static int __region_intersects(struct resource *parent, resource_size_t
> start,
> + size_t size, unsigned long flags,
> + unsigned long desc)
> {
> struct resource res;
> int type = 0; int other = 0;
> @@ -499,7 +500,7 @@ static int __region_intersects(resource_size_t start,
> size_t size,
> res.start = start;
> res.end = start + size - 1;
>
> - for (p = iomem_resource.child; p ; p = p->sibling) {
> + for (p = parent->child; p ; p = p->sibling) {
> bool is_type = (((p->flags & flags) == flags) &&
> ((desc == IORES_DESC_NONE) ||
> (desc == p->desc)));
> @@ -543,7 +544,7 @@ int region_intersects(resource_size_t start, size_t size,
> unsigned long flags,
> int ret;
>
> read_lock(&resource_lock);
> - ret = __region_intersects(start, size, flags, desc);
> + ret = __region_intersects(&iomem_resource, start, size, flags, desc);
> read_unlock(&resource_lock);
>
> return ret;
> @@ -1780,62 +1781,139 @@ void resource_list_free(struct list_head *head)
> }
> EXPORT_SYMBOL(resource_list_free);
>
> -#ifdef CONFIG_DEVICE_PRIVATE
> -static struct resource *__request_free_mem_region(struct device *dev,
> - struct resource *base, unsigned long size, const char *name)
> +#ifdef CONFIG_GET_FREE_REGION
> +#define GFR_DESCENDING (1UL << 0)
> +#define GFR_REQUEST_REGION (1UL << 1)
> +#define GFR_DEFAULT_ALIGN (1UL << PA_SECTION_SHIFT)
> +
> +static resource_size_t gfr_start(struct resource *base, resource_size_t size,
> + resource_size_t align, unsigned long flags)
> +{
> + if (flags & GFR_DESCENDING) {
> + resource_size_t end;
> +
> + end = min_t(resource_size_t, base->end,
> + (1ULL << MAX_PHYSMEM_BITS) - 1);
> + return end - size + 1;
> + }
> +
> + return ALIGN(base->start, align);
> +}
> +
> +static bool gfr_continue(struct resource *base, resource_size_t addr,
> + resource_size_t size, unsigned long flags)
> +{
> + if (flags & GFR_DESCENDING)
> + return addr > size && addr >= base->start;
> + /*
> + * In the ascend case be careful that the last increment by
> + * @size did not wrap 0.
> + */
> + return addr > addr - size &&
> + addr <= min_t(resource_size_t, base->end,
> + (1ULL << MAX_PHYSMEM_BITS) - 1);
> +}
> +
> +static resource_size_t gfr_next(resource_size_t addr, resource_size_t size,
> + unsigned long flags)
> +{
> + if (flags & GFR_DESCENDING)
> + return addr - size;
> + return addr + size;
> +}
> +
> +static void remove_free_mem_region(void *_res)
> +{
> + struct resource *res = _res;
> +
> + if (res->parent)
> + remove_resource(res);
> + free_resource(res);
> +}
> +
> +static struct resource *
> +get_free_mem_region(struct device *dev, struct resource *base,
> + resource_size_t size, const unsigned long align,
> + const char *name, const unsigned long desc,
> + const unsigned long flags)
> {
> - resource_size_t end, addr;
> + resource_size_t addr;
> struct resource *res;
> struct region_devres *dr = NULL;
>
> - size = ALIGN(size, 1UL << PA_SECTION_SHIFT);
> - end = min_t(unsigned long, base->end, (1UL << MAX_PHYSMEM_BITS) - 1);
> - addr = end - size + 1UL;
> + size = ALIGN(size, align);
>
> res = alloc_resource(GFP_KERNEL);
> if (!res)
> return ERR_PTR(-ENOMEM);
>
> - if (dev) {
> + if (dev && (flags & GFR_REQUEST_REGION)) {
> dr = devres_alloc(devm_region_release,
> sizeof(struct region_devres), GFP_KERNEL);
> if (!dr) {
> free_resource(res);
> return ERR_PTR(-ENOMEM);
> }
> + } else if (dev) {
> + if (devm_add_action_or_reset(dev, remove_free_mem_region, res))
> + return ERR_PTR(-ENOMEM);
> }
>
> write_lock(&resource_lock);
> - for (; addr > size && addr >= base->start; addr -= size) {
> - if (__region_intersects(addr, size, 0, IORES_DESC_NONE) !=
> - REGION_DISJOINT)
> + for (addr = gfr_start(base, size, align, flags);
> + gfr_continue(base, addr, size, flags);
> + addr = gfr_next(addr, size, flags)) {
> + if (__region_intersects(base, addr, size, 0, IORES_DESC_NONE) !=
> + REGION_DISJOINT)
> continue;
>
> - if (__request_region_locked(res, &iomem_resource, addr, size,
> - name, 0))
> - break;
> + if (flags & GFR_REQUEST_REGION) {
> + if (__request_region_locked(res, &iomem_resource, addr,
> + size, name, 0))
> + break;
>
> - if (dev) {
> - dr->parent = &iomem_resource;
> - dr->start = addr;
> - dr->n = size;
> - devres_add(dev, dr);
> - }
> + if (dev) {
> + dr->parent = &iomem_resource;
> + dr->start = addr;
> + dr->n = size;
> + devres_add(dev, dr);
> + }
>
> - res->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
> - write_unlock(&resource_lock);
> + res->desc = desc;
> + write_unlock(&resource_lock);
> +
> +
> + /*
> + * A driver is claiming this region so revoke any
> + * mappings.
> + */
> + revoke_iomem(res);
> + } else {
> + res->start = addr;
> + res->end = addr + size - 1;
> + res->name = name;
> + res->desc = desc;
> + res->flags = IORESOURCE_MEM;
> +
> + /*
> + * Only succeed if the resource hosts an exclusive
> + * range after the insert
> + */
> + if (__insert_resource(base, res) || res->child)
> + break;
> +
> + write_unlock(&resource_lock);
> + }
>
> - /*
> - * A driver is claiming this region so revoke any mappings.
> - */
> - revoke_iomem(res);
> return res;
> }
> write_unlock(&resource_lock);
>
> - free_resource(res);
> - if (dr)
> + if (flags & GFR_REQUEST_REGION) {
> + free_resource(res);
> devres_free(dr);
> + } else if (dev)
> + devm_release_action(dev, remove_free_mem_region, res);
>
> return ERR_PTR(-ERANGE);
> }
> @@ -1854,18 +1932,48 @@ static struct resource
> *__request_free_mem_region(struct device *dev,
> struct resource *devm_request_free_mem_region(struct device *dev,
> struct resource *base, unsigned long size)
> {
> - return __request_free_mem_region(dev, base, size, dev_name(dev));
> + unsigned long flags = GFR_DESCENDING | GFR_REQUEST_REGION;
> +
> + return get_free_mem_region(dev, base, size, GFR_DEFAULT_ALIGN,
> + dev_name(dev),
> + IORES_DESC_DEVICE_PRIVATE_MEMORY, flags);
> }
> EXPORT_SYMBOL_GPL(devm_request_free_mem_region);
>
> struct resource *request_free_mem_region(struct resource *base,
> unsigned long size, const char *name)
> {
> - return __request_free_mem_region(NULL, base, size, name);
> + unsigned long flags = GFR_DESCENDING | GFR_REQUEST_REGION;
> +
> + return get_free_mem_region(NULL, base, size, GFR_DEFAULT_ALIGN, name,
> + IORES_DESC_DEVICE_PRIVATE_MEMORY, flags);
> }
> EXPORT_SYMBOL_GPL(request_free_mem_region);
>
> -#endif /* CONFIG_DEVICE_PRIVATE */
> +/**
> + * alloc_free_mem_region - find a free region relative to @base
> + * @base: resource that will parent the new resource
> + * @size: size in bytes of memory to allocate from @base
> + * @align: alignment requirements for the allocation
> + * @name: resource name
> + *
> + * Buses like CXL, that can dynamically instantiate new memory regions,
> + * need a method to allocate physical address space for those regions.
> + * Allocate and insert a new resource to cover a free, unclaimed by a
> + * descendant of @base, range in the span of @base.
> + */
> +struct resource *alloc_free_mem_region(struct resource *base,
> + unsigned long size, unsigned long align,
> + const char *name)
> +{
> + /* Default of ascending direction and insert resource */
> + unsigned long flags = 0;
> +
> + return get_free_mem_region(NULL, base, size, align, name,
> + IORES_DESC_NONE, flags);
> +}
> +EXPORT_SYMBOL_NS_GPL(alloc_free_mem_region, CXL);
> +#endif /* CONFIG_GET_FREE_REGION */
>
> static int __init strict_iomem(char *str)
> {
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 169e64192e48..a5b4fee2e3fd 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -994,9 +994,14 @@ config HMM_MIRROR
> bool
> depends on MMU
>
> +config GET_FREE_REGION
> + depends on SPARSEMEM
> + bool
> +
> config DEVICE_PRIVATE
> bool "Unaddressable device memory (GPU memory, ...)"
> depends on ZONE_DEVICE
> + select GET_FREE_REGION
>
> help
> Allows creation of struct pages to represent unaddressable device
>
