Re: [PATCH 06/22] mm: factor out a devm_request_free_mem_region helper

John Hubbard
2019-06-15T02:21:56Z

On 6/13/19 2:43 AM, Christoph Hellwig wrote:
> Keep the physical address allocation that hmm_add_device does with the
> rest of the resource code, and allow future reuse of it without the hmm
> wrapper.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> include/linux/ioport.h | 2 ++
> kernel/resource.c | 39 +++++++++++++++++++++++++++++++++++++++
> mm/hmm.c | 33 ++++-----------------------------
> 3 files changed, 45 insertions(+), 29 deletions(-)

Some trivial typos noted below, but this accurately moves the code
into a helper routine, looks good.

Reviewed-by: John Hubbard <jhubbard@nvidia.com>

>
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index da0ebaec25f0..76a33ae3bf6c 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -286,6 +286,8 @@ static inline bool resource_overlaps(struct resource *r1, struct resource *r2)
> return (r1->start <= r2->end && r1->end >= r2->start);
> }
>
> +struct resource *devm_request_free_mem_region(struct device *dev,
> + struct resource *base, unsigned long size);
>
> #endif /* __ASSEMBLY__ */
> #endif /* _LINUX_IOPORT_H */
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 158f04ec1d4f..99c58134ed1c 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -1628,6 +1628,45 @@ void resource_list_free(struct list_head *head)
> }
> EXPORT_SYMBOL(resource_list_free);
>
> +#ifdef CONFIG_DEVICE_PRIVATE
> +/**
> + * devm_request_free_mem_region - find free region for device private memory
> + *
> + * @dev: device struct to bind the resource too

"to"

> + * @size: size in bytes of the device memory to add
> + * @base: resource tree to look in
> + *
> + * This function tries to find an empty range of physical address big enough to
> + * contain the new resource, so that it can later be hotpluged as ZONE_DEVICE

"hotplugged"

> + * memory, which in turn allocates struct pages.
> + */
> +struct resource *devm_request_free_mem_region(struct device *dev,
> + struct resource *base, unsigned long size)
> +{
> + resource_size_t end, addr;
> + struct resource *res;
> +
> + size = ALIGN(size, 1UL << PA_SECTION_SHIFT);
> + end = min_t(unsigned long, base->end, (1UL << MAX_PHYSMEM_BITS) - 1);
> + addr = end - size + 1UL;
> +
> + for (; addr > size && addr >= base->start; addr -= size) {
> + if (region_intersects(addr, size, 0, IORES_DESC_NONE) !=
> + REGION_DISJOINT)
> + continue;
> +
> + res = devm_request_mem_region(dev, addr, size, dev_name(dev));
> + if (!res)
> + return ERR_PTR(-ENOMEM);
> + res->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
> + return res;
> + }
> +
> + return ERR_PTR(-ERANGE);
> +}
> +EXPORT_SYMBOL_GPL(devm_request_free_mem_region);
> +#endif /* CONFIG_DEVICE_PRIVATE */
> +
> static int __init strict_iomem(char *str)
> {
> if (strstr(str, "relaxed"))
> diff --git a/mm/hmm.c b/mm/hmm.c
> index e1dc98407e7b..13a16faf0a77 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -26,8 +26,6 @@
> #include <linux/mmu_notifier.h>
> #include <linux/memory_hotplug.h>
>
> -#define PA_SECTION_SIZE (1UL << PA_SECTION_SHIFT)
> -
> #if IS_ENABLED(CONFIG_HMM_MIRROR)
> static const struct mmu_notifier_ops hmm_mmu_notifier_ops;
>
> @@ -1372,7 +1370,6 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
> unsigned long size)
> {
> struct hmm_devmem *devmem;
> - resource_size_t addr;
> void *result;
> int ret;
>
> @@ -1398,32 +1395,10 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
> if (ret)
> return ERR_PTR(ret);
>
> - size = ALIGN(size, PA_SECTION_SIZE);
> - addr = min((unsigned long)iomem_resource.end,
> - (1UL << MAX_PHYSMEM_BITS) - 1);
> - addr = addr - size + 1UL;
> -
> - /*
> - * FIXME add a new helper to quickly walk resource tree and find free
> - * range
> - *
> - * FIXME what about ioport_resource resource ?
> - */
> - for (; addr > size && addr >= iomem_resource.start; addr -= size) {
> - ret = region_intersects(addr, size, 0, IORES_DESC_NONE);
> - if (ret != REGION_DISJOINT)
> - continue;
> -
> - devmem->resource = devm_request_mem_region(device, addr, size,
> - dev_name(device));
> - if (!devmem->resource)
> - return ERR_PTR(-ENOMEM);
> - break;
> - }
> - if (!devmem->resource)
> - return ERR_PTR(-ERANGE);
> -
> - devmem->resource->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
> + devmem->resource = devm_request_free_mem_region(device, &iomem_resource,
> + size);
> + if (IS_ERR(devmem->resource))
> + return ERR_CAST(devmem->resource);
> devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
> devmem->pfn_last = devmem->pfn_first +
> (resource_size(devmem->resource) >> PAGE_SHIFT);
>

thanks,
--
John Hubbard
NVIDIA