[PATCH 6/6] ARM: mm: truncate memory banks to fit in 4GB space for classic MMU

On Tue, Mar 06, 2012 at 06:06:40PM +0000, Sergei Shtylyov wrote:

Hello.

Hi Sergei,

On 03/06/2012 07:54 PM, Will Deacon wrote:

quoted

If a bank of memory spanning the 4GB boundary is added on a !CONFIG_LPAE
kernel then we will hang early during boot since the memory bank will
have wrapped around to zero.

quoted

This patch truncates memory banks for !LPAE configurations when the end
address is not representable in 32 bits.

quoted

Signed-off-by: Will Deacon<redacted>
---
  arch/arm/kernel/setup.c |   11 ++++++++++-
  1 files changed, 10 insertions(+), 1 deletions(-)

quoted

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index a255c39..aeaa048 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c

@@ -521,7 +521,16 @@ int __init arm_add_memory(phys_addr_t start, unsigned long size)
  	 */
  	size -= start&  ~PAGE_MASK;
  	bank->start = PAGE_ALIGN(start);
-	bank->size  = size&  PAGE_MASK;
+
+#ifndef CONFIG_LPAE
+	if (bank->start + size<  bank->start) {
+		printk(KERN_CRIT "Truncating memory at 0x%08llx to fit in "
+			"32-bit physical address space\n", (long long)start);
+		size = ULONG_MAX - bank->start;

    I think you forgot to add one here.

No, I deliberately omit the last page because otherwise we end up with the
end address of the bank being calculated as 0, which leads to boot failure.

Will