From 62fb8adc43afad5fa1c9cadc6f3a8e9fb72af194 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Tue, 18 Feb 2025 15:22:05 -0700 Subject: mm: Provide address mask in struct follow_pfnmap_args follow_pfnmap_start() walks the page table for a given address and fills out the struct follow_pfnmap_args in pfnmap_args_setup(). The address mask of the page table level is already provided to this latter function for calculating the pfn. This address mask can also be useful for the caller to determine the extent of the contiguous mapping. For example, vfio-pci now supports huge_fault for pfnmaps and is able to insert pud and pmd mappings. When we DMA map these pfnmaps, ex. PCI MMIO BARs, we iterate follow_pfnmap_start() to get each pfn to test for a contiguous pfn range. Providing the mapping address mask allows us to skip the extent of the mapping level. Assuming a 1GB pud level and 4KB page size, iterations are reduced by a factor of 256K. In wall clock time, mapping a 32GB PCI BAR is reduced from ~1s to <1ms. Cc: Andrew Morton Cc: David Hildenbrand Cc: linux-mm@kvack.org Reviewed-by: Peter Xu Reviewed-by: Mitchell Augustin Tested-by: Mitchell Augustin Reviewed-by: Jason Gunthorpe Acked-by: David Hildenbrand Link: https://lore.kernel.org/r/20250218222209.1382449-6-alex.williamson@redhat.com Signed-off-by: Alex Williamson --- include/linux/mm.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/mm.h') diff --git a/include/linux/mm.h b/include/linux/mm.h index 7b1068ddcbb7..92b30dba7e38 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2417,11 +2417,13 @@ struct follow_pfnmap_args { * Outputs: * * @pfn: the PFN of the address + * @addr_mask: address mask covering pfn * @pgprot: the pgprot_t of the mapping * @writable: whether the mapping is writable * @special: whether the mapping is a special mapping (real PFN maps) */ unsigned long pfn; + unsigned long addr_mask; pgprot_t pgprot; bool writable; bool special; -- cgit v1.2.3