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authorWu Fengguang <fengguang.wu@intel.com>2010-03-01 21:55:51 +0800
committerH. Peter Anvin <hpa@zytor.com>2010-03-01 10:18:32 -0800
commit37b99dd5372cff42f83210c280f314f10f99138e (patch)
treeb5fd741c214f308373232c26e82be9c7628c285c /kernel
parentdad52fc01161afcb8798c609e009aed4d104927f (diff)
downloadlwn-37b99dd5372cff42f83210c280f314f10f99138e.tar.gz
lwn-37b99dd5372cff42f83210c280f314f10f99138e.zip
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: > >>> [<ffffffff81047cff>] ? __ioremap_caller+0x169/0x2f1 > >>> [<ffffffff81063b7d>] warn_slowpath_common+0x77/0xa4 > >>> [<ffffffff81063bb9>] warn_slowpath_null+0xf/0x11 > >>> [<ffffffff81047cff>] __ioremap_caller+0x169/0x2f1 > >>> [<ffffffff813747a3>] ? acpi_os_map_memory+0x12/0x1b > >>> [<ffffffff81047f10>] ioremap_nocache+0x12/0x14 > >>> [<ffffffff813747a3>] acpi_os_map_memory+0x12/0x1b > >>> [<ffffffff81282fa0>] acpi_tb_verify_table+0x29/0x5b > >>> [<ffffffff812827f0>] acpi_load_tables+0x39/0x15a > >>> [<ffffffff8191c8f8>] acpi_early_init+0x60/0xf5 > >>> [<ffffffff818f2cad>] start_kernel+0x397/0x3a7 > >>> [<ffffffff818f2295>] x86_64_start_reservations+0xa5/0xa9 > >>> [<ffffffff818f237a>] 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 <sachinp@in.ibm.com> CC: Thomas Gleixner <tglx@linutronix.de> CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> LKML-Reference: <20100301135551.GA9998@localhost> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/resource.c9
1 files 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;