2013-06-09 09:42:28

by Shan Wei

Subject: [PATCH buf-fix] kernel, range: fix broken mtrr_cleanup

From: Samuel Liao <[email protected]>


commit fbe06b7bae7c9cf6ab05168fce5ee93b2f4bae7c broken the mtrr_cleanup
due to return incorrect merged range. this patch remove the empty range
by swapping with the last.

Error messages:
Jun 9 14:06:18 kernel: [ 0.000000] *BAD*gran_size: 64K chunk_size: 64K num_reg: 4 lose cover RAM: -0G
Jun 9 14:06:18 kernel: [ 0.000000] *BAD*gran_size: 64K chunk_size: 128K num_reg: 4 lose cover RAM: -0G
Jun 9 14:06:18 kernel: [ 0.000000] *BAD*gran_size: 64K chunk_size: 256K num_reg: 4 lose cover RAM: -0G
Jun 9 14:06:18 kernel: [ 0.000000] *BAD*gran_size: 64K chunk_size: 512K num_reg: 4 lose cover RAM: -0G


Signed-off-by: Samuel Liao <[email protected]>
---
kernel/range.c | 15 ++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/kernel/range.c b/kernel/range.c
index eb911db..b723697 100644
--- a/kernel/range.c
+++ b/kernel/range.c
@@ -48,11 +48,18 @@ int add_range_with_merge(struct range *range, int az, int nr_range,
final_start = min(range[i].start, start);
final_end = max(range[i].end, end);

+ if (final_start == range[i].start && final_end == range[i].end)
+ return nr_range;
+
/* clear it and add it back for further merge */
- range[i].start = 0;
- range[i].end = 0;
- return add_range_with_merge(range, az, nr_range,
- final_start, final_end);
+ nr_range -= 1;
+ if (i != nr_range) {
+ range[i].start = range[nr_range].start;
+ range[i].end = range[nr_range].end;
+ }
+ range[nr_range].start = 0;
+ range[nr_range].end = 0;
+ i = -1;
}

/* Need to add it: */
--
1.8.2.1

2013-06-09 21:34:15

by Yinghai Lu

Subject: Re: [PATCH buf-fix] kernel, range: fix broken mtrr_cleanup

On Sun, Jun 9, 2013 at 2:42 AM, Shan Wei <[email protected]> wrote:
> From: Samuel Liao <[email protected]>
>
>
> commit fbe06b7bae7c9cf6ab05168fce5ee93b2f4bae7c broken the mtrr_cleanup
> due to return incorrect merged range. this patch remove the empty range
> by swapping with the last.
>
> Error messages:
> Jun 9 14:06:18 kernel: [ 0.000000] *BAD*gran_size: 64K chunk_size: 64K num_reg: 4 lose cover RAM: -0G
> Jun 9 14:06:18 kernel: [ 0.000000] *BAD*gran_size: 64K chunk_size: 128K num_reg: 4 lose cover RAM: -0G
> Jun 9 14:06:18 kernel: [ 0.000000] *BAD*gran_size: 64K chunk_size: 256K num_reg: 4 lose cover RAM: -0G
> Jun 9 14:06:18 kernel: [ 0.000000] *BAD*gran_size: 64K chunk_size: 512K num_reg: 4 lose cover RAM: -0G
>
>
> Signed-off-by: Samuel Liao <[email protected]>
> ---
> kernel/range.c | 15 ++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/range.c b/kernel/range.c
> index eb911db..b723697 100644
> --- a/kernel/range.c
> +++ b/kernel/range.c
> @@ -48,11 +48,18 @@ int add_range_with_merge(struct range *range, int az, int nr_range,
> final_start = min(range[i].start, start);
> final_end = max(range[i].end, end);
>
> + if (final_start == range[i].start && final_end == range[i].end)
> + return nr_range;
> +
> /* clear it and add it back for further merge */
> - range[i].start = 0;
> - range[i].end = 0;
> - return add_range_with_merge(range, az, nr_range,
> - final_start, final_end);
> + nr_range -= 1;
> + if (i != nr_range) {
> + range[i].start = range[nr_range].start;
> + range[i].end = range[nr_range].end;
> + }
> + range[nr_range].start = 0;
> + range[nr_range].end = 0;
> + i = -1;
> }
>
> /* Need to add it: */

this patch is totally wrong.

if the ranges already have [0,1g), [2g, 3g). and want to add [1g, 2g) to it.

what is the result after this patch?
only [1g, 2g)

Thanks

Yinghai

2013-06-13 02:28:27

by samuelliao(廖生苗)

Subject: Re: [PATCH buf-fix] kernel, range: fix broken mtrr_cleanup(Internet mail)

I forget change final_start/final_end to start/end. The old code add empty range in following case:

Before mtrr cleanup:
1. got initial MTRR range: 0-3G.
2. MTRR code try to merge 0-1M
3. result is 0-0, 0-3G, total 2 range count

After cleanup:
1. got final MTRR range: 0-3G, total 1 range count

the cleanup code failed, because range count mismatch.
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