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SubjectRe: [BUG 2.6.31-rc1] HIGHMEM64G causes hang in PCI init on 32-bit x86
Linus Torvalds wrote:
>
> On Mon, 29 Jun 2009, Yinghai Lu wrote:
>> + end = round_up(start, ram_alignment(start)) - 1;
>> + if (start > (resource_size_t)end)
>> continue;
>> - reserve_region_with_split(&iomem_resource, start,
>> - end - 1, "RAM buffer");
>> + reserve_region_with_split(&iomem_resource, (resource_size_t)start,
>> + (resource_size_t)end, "RAM buffer");
>
> Hmm. You shouldn't need the casts with reserve_region_with_split(), and
> they just make things uglier.
>
> Also, I wonder if we should do something like this instead
>
> #define MAX_RESOURCE_SIZE ((resource_size_t)-1)
>
> ...
> end = round_up(start, ram_alignment(start)) - 1;
> if (end > MAX_RESOURCE_SIZE)
> end = MAX_RESOURCE_SIZE;
> if (start > end)
> continue;
>
> Because otherwise we'll just be ignoring resources that cross the resource
> size boundary, which sounds wrong.
>
> We _could_ have a RAM resource that crosses the 4GB boundary, after all.
>
> Yeah, it doesn't happen much in practice, because usually the 3G-4G range
> is left for PCI mappings etc, so we might never hit this in practice, but
> still, this sounds like a more correct thing to do.
>
> It also avoids the cast. We simply cap the end to the max that
> 'resource_size_t' can hold.

Mikael, please try this on your system, and send out /proc/iomem

Thanks

Yinghai

[PATCH] x86: add boundary check for 32bit res before expand e820 resource to alignment

fix hang with HIGHMEM_64G and 32bit resource.

according to hpa and Linus, use (resource_size_t)-1 to fend off big ranges.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
arch/x86/kernel/e820.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)

Index: linux-2.6/arch/x86/kernel/e820.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/e820.c
+++ linux-2.6/arch/x86/kernel/e820.c
@@ -1367,9 +1367,9 @@ void __init e820_reserve_resources(void)
}

/* How much should we pad RAM ending depending on where it is? */
-static unsigned long ram_alignment(resource_size_t pos)
+static u64 ram_alignment(u64 pos)
{
- unsigned long mb = pos >> 20;
+ u64 mb = pos >> 20;

/* To 64kB in the first megabyte */
if (!mb)
@@ -1383,6 +1383,8 @@ static unsigned long ram_alignment(resou
return 32*1024*1024;
}

+#define MAX_RESOURCE_SIZE ((resource_size_t)-1)
+
void __init e820_reserve_resources_late(void)
{
int i;
@@ -1400,17 +1402,19 @@ void __init e820_reserve_resources_late(
* avoid stolen RAM:
*/
for (i = 0; i < e820.nr_map; i++) {
- struct e820entry *entry = &e820_saved.map[i];
- resource_size_t start, end;
+ struct e820entry *entry = &e820.map[i];
+ u64 start, end;

if (entry->type != E820_RAM)
continue;
start = entry->addr + entry->size;
- end = round_up(start, ram_alignment(start));
- if (start == end)
+ end = round_up(start, ram_alignment(start)) - 1;
+ if (end > MAX_RESOURCE_SIZE)
+ end = MAX_RESOURCE_SIZE;
+ if (start > end)
continue;
- reserve_region_with_split(&iomem_resource, start,
- end - 1, "RAM buffer");
+ reserve_region_with_split(&iomem_resource, start, end,
+ "RAM buffer");
}
}



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