On 7/11/23 3:53 PM, David Hildenbrand wrote:
>> -bool mhp_supports_memmap_on_memory(unsigned long size)
>> +static bool mhp_supports_memmap_on_memory(unsigned long size)
>> {
>> unsigned long nr_vmemmap_pages = size / PAGE_SIZE;
>> unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page);
>> @@ -1339,13 +1339,12 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
>> * Self hosted memmap array
>> */
>> if (mhp_flags & MHP_MEMMAP_ON_MEMORY) {
>> - if (!mhp_supports_memmap_on_memory(size)) {
>> - ret = -EINVAL;
>> - goto error;
>> + if (mhp_supports_memmap_on_memory(size)) {
>> + mhp_altmap.free = PHYS_PFN(size);
>> + mhp_altmap.base_pfn = PHYS_PFN(start);
>> + params.altmap = &mhp_altmap;
>> }
>> - mhp_altmap.free = PHYS_PFN(size);
>> - mhp_altmap.base_pfn = PHYS_PFN(start);
>> - params.altmap = &mhp_altmap;
>> + /* fallback to not using altmap */
>> }
>> /* call arch's memory hotadd */
>
> In general, LGTM, but please extend the documentation of the parameter in memory_hotplug.h, stating that this is just a hint and that the core can decide to no do that.
>
will update
modified include/linux/memory_hotplug.h
@@ -97,6 +97,8 @@ typedef int __bitwise mhp_t;
* To do so, we will use the beginning of the hot-added range to build
* the page tables for the memmap array that describes the entire range.
* Only selected architectures support it with SPARSE_VMEMMAP.
+ * This is only a hint, core kernel can decide to not do this based on
+ * different alignment checks.
*/
#define MHP_MEMMAP_ON_MEMORY ((__force mhp_t)BIT(1))
