On 30.11.20 04:29, Anshuman Khandual wrote:
> This introduces memhp_range_allowed() which can be called in various memory
> hotplug paths to prevalidate the address range which is being added, with
> the platform. Then memhp_range_allowed() calls memhp_get_pluggable_range()
> which provides applicable address range depending on whether linear mapping
> is required or not. For ranges that require linear mapping, it calls a new
> arch callback arch_get_mappable_range() which the platform can override. So
> the new callback, in turn provides the platform an opportunity to configure
> acceptable memory hotplug address ranges in case there are constraints.
>
> This mechanism will help prevent platform specific errors deep down during
> hotplug calls. This drops now redundant check_hotplug_memory_addressable()
> check in __add_pages().
>
[...]
> /*
> * Reasonably generic function for adding memory. It is
> * expected that archs that support memory hotplug will
> @@ -317,10 +304,6 @@ int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages,
> if (WARN_ON_ONCE(!params->pgprot.pgprot))
> return -EINVAL;
>
> - err = check_hotplug_memory_addressable(pfn, nr_pages);
> - if (err)
> - return err;
> -
I was wondering if we should add a VM_BUG_ON(!memhp_range_allowed())
here to make it clearer that callers are expected to check that first.
Maybe an other places as well (e.g., arch code where we remove the
original checks)
[...]
> #endif /* CONFIG_MEMORY_HOTREMOVE */
> diff --git a/mm/memremap.c b/mm/memremap.c
> index 16b2fb482da1..26c1825756cc 100644
> --- a/mm/memremap.c
> +++ b/mm/memremap.c
> @@ -185,6 +185,7 @@ static void dev_pagemap_percpu_release(struct percpu_ref *ref)
> static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params,
> int range_id, int nid)
> {
> + const bool is_private = pgmap->type == MEMORY_DEVICE_PRIVATE;
> struct range *range = &pgmap->ranges[range_id];
> struct dev_pagemap *conflict_pgmap;
> int error, is_ram;
> @@ -230,6 +231,9 @@ static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params,
> if (error)
> goto err_pfn_remap;
>
> + if (!memhp_range_allowed(range->start, range_len(range), !is_private))
> + goto err_pfn_remap;
> +
> mem_hotplug_begin();
>
> /*
> @@ -243,7 +247,7 @@ static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params,
> * the CPU, we do want the linear mapping and thus use
> * arch_add_memory().
> */
> - if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
> + if (is_private) {
> error = add_pages(nid, PHYS_PFN(range->start),
> PHYS_PFN(range_len(range)), params);
> } else {
>
In general, LGTM.
--
Thanks,
David / dhildenb
