From 4270fd8b4c27f08b9cfd7e2fc342d1a31217ba6b Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Sat, 28 Jan 2017 12:45:40 +0100 Subject: x86/boot/e820: Move the memblock_find_dma_reserve() function and rename it to memblock_set_dma_reserve() We introduced memblock_find_dma_reserve() in this commit: 6f2a75369e75 x86, memblock: Use memblock_memory_size()/memblock_free_memory_size() to get correct dma_reserve But there's several problems with it: - The changelog is full of typos and is incomprehensible in general, and the comments in the code are not much better either. - The function was inexplicably placed into e820.c, while it has very little connection to the E820 table: when we call memblock_find_dma_reserve() then memblock is already set up and we are not using the E820 table anymore. - The function is a wrapper around set_dma_reserve(), but changed the 'set' name to 'find' - actively misleading about its primary purpose, which is still to set the DMA-reserve value. - The function is limited to 64-bit systems, but neither the changelog nor the comments explain why. The change would appear to be relevant to 32-bit systems as well, as the ISA DMA zone is the first 16 MB of RAM. So address some of these problems: - Move it into arch/x86/mm/init.c, next to the other zone setup related functions. - Clean up the code flow and names of local variables a bit. - Rename it to memblock_set_dma_reserve() - Improve the comments. No change in functionality. Enabling it for 32-bit systems is left for a separate patch. Cc: Alex Thorlton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Dan Williams Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Huang, Ying Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Linus Torvalds Cc: Paul Jackson Cc: Peter Zijlstra Cc: Rafael J. Wysocki Cc: Tejun Heo Cc: Thomas Gleixner Cc: Wei Yang Cc: Yinghai Lu Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- arch/x86/mm/init.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) (limited to 'arch/x86/mm/init.c') diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index b7b4ad569d13..922671d3af85 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -724,6 +724,53 @@ void __init free_initrd_mem(unsigned long start, unsigned long end) } #endif +/* + * Calculate the precise size of the DMA zone (first 16 MB of RAM), + * and pass it to the MM layer - to help it set zone watermarks more + * accurately. + * + * Done on 64-bit systems only for the time being, although 32-bit systems + * might benefit from this as well. + */ +void __init memblock_find_dma_reserve(void) +{ +#ifdef CONFIG_X86_64 + u64 nr_pages = 0, nr_free_pages = 0; + unsigned long start_pfn, end_pfn; + phys_addr_t start_addr, end_addr; + int i; + u64 u; + + /* + * Iterate over all memory ranges (free and reserved ones alike), + * to calculate the total number of pages in the first 16 MB of RAM: + */ + nr_pages = 0; + for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, NULL) { + start_pfn = min(start_pfn, MAX_DMA_PFN); + end_pfn = min(end_pfn, MAX_DMA_PFN); + + nr_pages += end_pfn - start_pfn; + } + + /* + * Iterate over free memory ranges to calculate the number of free + * pages in the DMA zone, while not counting potential partial + * pages at the beginning or the end of the range: + */ + nr_free_pages = 0; + for_each_free_mem_range(u, NUMA_NO_NODE, MEMBLOCK_NONE, &start_addr, &end_addr, NULL) { + start_pfn = min_t(unsigned long, PFN_UP(start_addr), MAX_DMA_PFN); + end_pfn = min_t(unsigned long, PFN_DOWN(end_addr), MAX_DMA_PFN); + + if (start_pfn < end_pfn) + nr_free_pages += end_pfn - start_pfn; + } + + set_dma_reserve(nr_pages - nr_free_pages); +#endif +} + void __init zone_sizes_init(void) { unsigned long max_zone_pfns[MAX_NR_ZONES]; -- cgit v1.2.3