| Message ID | 20220624041950.559155-8-dan.j.williams@intel.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | CXL PMEM Region Provisioning | expand |
On Thu, 23 Jun 2022 21:19:37 -0700 Dan Williams <dan.j.williams@intel.com> 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()). > > Suggested-by: Jason Gunthorpe <jgg@nvidia.com> > Link: https://lore.kernel.org/linux-cxl/20220420143406.GY2120790@nvidia.com/ > Cc: Matthew Wilcox <willy@infradead.org> > Cc: Christoph Hellwig <hch@infradead.org> > Signed-off-by: Dan Williams <dan.j.williams@intel.com> A few things inline, Thanks, Jonathan > --- > include/linux/ioport.h | 2 + > kernel/resource.c | 174 ++++++++++++++++++++++++++++++++--------- > mm/Kconfig | 5 ++ > 3 files changed, 146 insertions(+), 35 deletions(-) > > diff --git a/include/linux/ioport.h b/include/linux/ioport.h > index ec5f71f7135b..ed03518347aa 100644 > --- a/include/linux/ioport.h > +++ b/include/linux/ioport.h > @@ -329,6 +329,8 @@ 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..9fc990274106 100644 > --- a/kernel/resource.c > +++ b/kernel/resource.c > +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; > + return addr > addr - size && Is this checking for wrap around? If so maybe a comment to call that out? > + 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) > { > - resource_size_t end, addr; > + 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 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); slightly nicer to return whatever value you got back from devm_add_action_or_reset() > } > > 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); The original if (dr) was unnecessary as devres_free() checks. Looking just at this patch it looks like you aren't covering the corner case of dev == NULL and GFR_REQUEST_REGION. Perhaps worth a tiny comment in patch description? (doesn't seem worth pulling this change out as a precursor given it's so small). Of add the extra if (dr) back in to 'document' that no change... > + } else if (dev) > + devm_release_action(dev, remove_free_mem_region, res); > > return ERR_PTR(-ERANGE); > } > @@ -1854,18 +1928,48 @@ 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, Given the extra align parameter, does it make sense to give this a naming that highlights that vs the other two interfaces above? alloc_free_mem_region_aligned() > + unsigned long size, unsigned long align, > + const char *name) > +{ > + /* GFR_ASCENDING | GFR_INSERT_RESOURCE */ Given those flags don't exist and some fool like me might grep for them perhaps better to describe it in text /* 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
Jonathan Cameron wrote: > On Thu, 23 Jun 2022 21:19:37 -0700 > Dan Williams <dan.j.williams@intel.com> 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()). > > > > Suggested-by: Jason Gunthorpe <jgg@nvidia.com> > > Link: https://lore.kernel.org/linux-cxl/20220420143406.GY2120790@nvidia.com/ > > Cc: Matthew Wilcox <willy@infradead.org> > > Cc: Christoph Hellwig <hch@infradead.org> > > Signed-off-by: Dan Williams <dan.j.williams@intel.com> > > A few things inline, > > Thanks, > > Jonathan > > > --- > > include/linux/ioport.h | 2 + > > kernel/resource.c | 174 ++++++++++++++++++++++++++++++++--------- > > mm/Kconfig | 5 ++ > > 3 files changed, 146 insertions(+), 35 deletions(-) > > > > diff --git a/include/linux/ioport.h b/include/linux/ioport.h > > index ec5f71f7135b..ed03518347aa 100644 > > --- a/include/linux/ioport.h > > +++ b/include/linux/ioport.h > > @@ -329,6 +329,8 @@ 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..9fc990274106 100644 > > --- a/kernel/resource.c > > +++ b/kernel/resource.c > > > > +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; > > + return addr > addr - size && > > Is this checking for wrap around? If so maybe a comment to call that out? Yes, and ok. > > > + 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) > > { > > - resource_size_t end, addr; > > + 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 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); > > slightly nicer to return whatever value you got back from devm_add_action_or_reset() Yes, but it is known to only return -ENOMEM on failure and saves adding a local @rc variable. > > > } > > > > 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); > > The original if (dr) was unnecessary as devres_free() checks. > > Looking just at this patch it looks like you aren't covering the > corner case of dev == NULL and GFR_REQUEST_REGION. > > Perhaps worth a tiny comment in patch description? (doesn't seem worth > pulling this change out as a precursor given it's so small). > Of add the extra if (dr) back in to 'document' that no change... Added to the changelog: 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. > > > > + } else if (dev) > > + devm_release_action(dev, remove_free_mem_region, res); > > > > return ERR_PTR(-ERANGE); > > } > > @@ -1854,18 +1928,48 @@ 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, > Given the extra align parameter, does it make sense to give this a naming > that highlights that vs the other two interfaces above? > > alloc_free_mem_region_aligned() The other variants are also aligned, they just aren't variably aligned, they are implicitly aligned to GFR_DEFAULT_ALIGN. So I think calling this one _aligned() betrays what is happening in the other cases. > > + unsigned long size, unsigned long align, > > + const char *name) > > +{ > > + /* GFR_ASCENDING | GFR_INSERT_RESOURCE */ > > Given those flags don't exist and some fool like me might grep for them > perhaps better to describe it in text > > /* Default of ascending direction and insert resource */ Ok.
diff --git a/include/linux/ioport.h b/include/linux/ioport.h index ec5f71f7135b..ed03518347aa 100644 --- a/include/linux/ioport.h +++ b/include/linux/ioport.h @@ -329,6 +329,8 @@ 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..9fc990274106 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 +1781,135 @@ 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; + 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) { - resource_size_t end, addr; + 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 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 +1928,48 @@ 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) +{ + /* GFR_ASCENDING | GFR_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
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()). Suggested-by: Jason Gunthorpe <jgg@nvidia.com> Link: https://lore.kernel.org/linux-cxl/20220420143406.GY2120790@nvidia.com/ Cc: Matthew Wilcox <willy@infradead.org> Cc: Christoph Hellwig <hch@infradead.org> Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- include/linux/ioport.h | 2 + kernel/resource.c | 174 ++++++++++++++++++++++++++++++++--------- mm/Kconfig | 5 ++ 3 files changed, 146 insertions(+), 35 deletions(-)