On Mon, Jan 25, 2021 at 12:43:23PM +0100, David Hildenbrand wrote:

quoted

-	if (end - start < PAGES_PER_SECTION * sizeof(struct page))
+	if (is_hugetlb_free_vmemmap_enabled() ||
+	    end - start < PAGES_PER_SECTION * sizeof(struct page))

This looks irresponsible. You ignore any altmap, even though current
altmap users (ZONE_DEVICE) will not actually result in applicable
vmemmaps that huge pages could ever use.

Why do you ignore the altmap completely? This has to be properly
documented, but IMHO it's not even the right approach to mess with
altmap here.

The goal was not to ignore altmap but to disable PMD mapping sections
when the feature was enabled.
Shame on me I did not notice that with this, altmap will be ignored.

Something like below maybe:

int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
                struct vmem_altmap *altmap)
{
        int err;
        bool populate_base_pages = false;

        if ((end - start < PAGES_PER_SECTION * sizeof(struct page)) ||
            (is_hugetlb_free_vmemmap_enabled() && !altmap))
                populate_base_pages = true;

        if (populate_base_pages) {
                err = vmemmap_populate_basepages(start, end, node, NULL);
        } else if (boot_cpu_has(X86_FEATURE_PSE)) {
	....

-- 
Thanks,

David / dhildenb

-- 
Oscar Salvador
SUSE L3