Memory range end be inclusive or exclusive? Re: [PATCH v1 1/4] kexec: (bugfix) calc correct end address of memory ranges in device tree

Simon,

On Tue, Sep 06, 2016 at 09:29:59AM +0900, AKASHI Takahiro wrote:

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Simon,

What is your opinion on this issue?

Pinged you several times so far.

Can you please give me your comment?
(attached below is the original patch.)

-Takahiro AKASHI

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On Mon, Aug 01, 2016 at 01:52:40PM +0900, AKASHI Takahiro wrote:

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On Fri, Jul 29, 2016 at 06:23:56PM +0100, Russell King - ARM Linux wrote:

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On Fri, Jul 29, 2016 at 10:12:26AM -0700, Geoff Levand wrote:

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On Fri, 2016-07-29 at 09:27 +0100, Russell King - ARM Linux wrote:

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So, these functions are a mess and need fixing.

Since this change isn't really related to arm64 support, I'll
drop this patch from my series.

Do you have a case which triggers bugs in this code?

Actually, this patch was necessary when my kdump used "usable-memory"
properties in "memory" nodes, as on ppc64, to limit the usable memory
regions that can be used by crash dump kernel.
Since then, I've moved to the approach of using "mem=" kernel parameter,
then introducing a new property, "linux,usable-memory-range," under /chosen
and now we don't need this patch any more.

So, we can drop it but I still believe that it is buggy.

Due to the discussions[1], I may want to re-enable "usable-memory"
property on arm64. In addition, I would like to add a function,
dtb_add_usable_memory_properties(), a variant of
add_usable_memory_properties(), to kexec/dt-ops.c.
So this issue is quite crucial now.

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-August/452685.html

-Takahiro AKASHI

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Thanks,
-Takahiro AKASHI

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===8<===
From: AKASHI Takahiro <redacted>

The end address of "reg" attribute in device tree's memory should be
inclusive.
---
 kexec/fs2dt.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kexec/fs2dt.c b/kexec/fs2dt.c
index 79aa0f3..953f78a 100644
--- a/kexec/fs2dt.c
+++ b/kexec/fs2dt.c

@@ -236,7 +236,8 @@ static void add_dyn_reconf_usable_mem_property__(int fd)
 						    ranges_size*8);
 				}
 				ranges[rlen++] = cpu_to_be64(loc_base);
-				ranges[rlen++] = cpu_to_be64(loc_end - loc_base);
+				ranges[rlen++] = cpu_to_be64(loc_end
+								- loc_base + 1);
 				rngs_cnt++;
 			}
 		}

@@ -350,7 +351,7 @@ static void add_usable_mem_property(int fd, size_t len)
 					    ranges_size*sizeof(*ranges));
 			}
 			ranges[rlen++] = cpu_to_be64(loc_base);
-			ranges[rlen++] = cpu_to_be64(loc_end - loc_base);
+			ranges[rlen++] = cpu_to_be64(loc_end - loc_base + 1);
 		}
 	}
 

-- 
2.10.0