From 37b99dd5372cff42f83210c280f314f10f99138e Mon Sep 17 00:00:00 2001 From: Wu Fengguang Date: Mon, 1 Mar 2010 21:55:51 +0800 Subject: [PATCH] resource: Fix generic page_is_ram() for partial RAM pages The System RAM walk shall skip partial RAM pages and avoid calling func() on them. So that page_is_ram() return 0 for a partial RAM page. In particular, it shall not call func() with len=0. This fixes a boot time bug reported by Sachin and root caused by Thomas: > >>> WARNING: at arch/x86/mm/ioremap.c:111 __ioremap_caller+0x169/0x2f1() > >>> Hardware name: BladeCenter LS21 -[79716AA]- > >>> Modules linked in: > >>> Pid: 0, comm: swapper Not tainted 2.6.33-git6-autotest #1 > >>> Call Trace: > >>> [] ? __ioremap_caller+0x169/0x2f1 > >>> [] warn_slowpath_common+0x77/0xa4 > >>> [] warn_slowpath_null+0xf/0x11 > >>> [] __ioremap_caller+0x169/0x2f1 > >>> [] ? acpi_os_map_memory+0x12/0x1b > >>> [] ioremap_nocache+0x12/0x14 > >>> [] acpi_os_map_memory+0x12/0x1b > >>> [] acpi_tb_verify_table+0x29/0x5b > >>> [] acpi_load_tables+0x39/0x15a > >>> [] acpi_early_init+0x60/0xf5 > >>> [] start_kernel+0x397/0x3a7 > >>> [] x86_64_start_reservations+0xa5/0xa9 > >>> [] x86_64_start_kernel+0xe1/0xe8 > >>> ---[ end trace 4eaa2a86a8e2da22 ]--- > >>> ioremap reserve_memtype failed -22 The return code is -EINVAL, so it failed in the is_ram check, which is not too surprising > BIOS-provided physical RAM map: > BIOS-e820: 0000000000000000 - 000000000009c000 (usable) > BIOS-e820: 000000000009c000 - 00000000000a0000 (reserved) > BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved) > BIOS-e820: 0000000000100000 - 00000000cffa3900 (usable) > BIOS-e820: 00000000cffa3900 - 00000000cffa7400 (ACPI data) The ACPI data is not starting on a page boundary and neither does the usable RAM area end on a page boundary. Very useful ! > ACPI: DSDT 00000000cffa3900 036CE (v01 IBM SERLEWIS 00001000 INTL 20060912) ACPI is trying to map DSDT at cffa3900, which results in a check vs. cffa3000 which is the relevant page boundary. The generic is_ram check correctly identifies that as RAM because it's in the usable resource area. The old e820 based is_ram check does not take overlapping resource areas into account. That's why it works. CC: Sachin Sant CC: Thomas Gleixner CC: KAMEZAWA Hiroyuki Signed-off-by: Wu Fengguang LKML-Reference: <20100301135551.GA9998@localhost> Signed-off-by: H. Peter Anvin --- kernel/resource.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/kernel/resource.c b/kernel/resource.c index 03c897f7935e..8f0e3d0f4bff 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -274,7 +274,7 @@ int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages, void *arg, int (*func)(unsigned long, unsigned long, void *)) { struct resource res; - unsigned long pfn, len; + unsigned long pfn, end_pfn; u64 orig_end; int ret = -1; @@ -284,9 +284,10 @@ int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages, orig_end = res.end; while ((res.start < res.end) && (find_next_system_ram(&res, "System RAM") >= 0)) { - pfn = (unsigned long)(res.start >> PAGE_SHIFT); - len = (unsigned long)((res.end + 1 - res.start) >> PAGE_SHIFT); - ret = (*func)(pfn, len, arg); + pfn = (res.start + PAGE_SIZE - 1) >> PAGE_SHIFT; + end_pfn = (res.end + 1) >> PAGE_SHIFT; + if (end_pfn > pfn) + ret = (*func)(pfn, end_pfn - pfn, arg); if (ret) break; res.start = res.end + 1;