2009-01-28 08:55:50

by Lubomir Rintel

Subject: [PATCH] Fix a panic with 1M of shared memory, no GTT entries

When GTT size is equal to amount of video memory, the amount of GTT
entries is computed lower than zero, which is invalid and leads to
off-by-one error in intel_i915_configure()

Originally posted here:
http://bugzilla.kernel.org/show_bug.cgi?id=12539
http://bugzilla.redhat.com/show_bug.cgi?id=445592

Signed-Off-By: Lubomir Rintel <[email protected]>
---
drivers/char/agp/intel-agp.c | 8 +++++---
1 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/char/agp/intel-agp.c b/drivers/char/agp/intel-agp.c
index c771418..4373adb 100644
--- a/drivers/char/agp/intel-agp.c
+++ b/drivers/char/agp/intel-agp.c
@@ -633,13 +633,15 @@ static void intel_i830_init_gtt_entries(void)
break;
}
}
- if (gtt_entries > 0)
+ if (gtt_entries > 0) {
dev_info(&agp_bridge->dev->dev, "detected %dK %s memory\n",
gtt_entries / KB(1), local ? "local" : "stolen");
- else
+ gtt_entries /= KB(4);
+ } else {
dev_info(&agp_bridge->dev->dev,
"no pre-allocated video memory detected\n");
- gtt_entries /= KB(4);
+ gtt_entries = 0;
+ }

intel_private.gtt_entries = gtt_entries;
}
--
1.5.5.6

2009-01-28 09:13:23

by Dave Airlie

Subject: Re: [PATCH] Fix a panic with 1M of shared memory, no GTT entries

> When GTT size is equal to amount of video memory, the amount of GTT
> entries is computed lower than zero, which is invalid and leads to
> off-by-one error in intel_i915_configure()
>
> Originally posted here:
> http://bugzilla.kernel.org/show_bug.cgi?id=12539
> http://bugzilla.redhat.com/show_bug.cgi?id=445592

cc'ed Intel agp knowledge.

Dave.

>
> Signed-Off-By: Lubomir Rintel <[email protected]>
> ---
> drivers/char/agp/intel-agp.c | 8 +++++---
> 1 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/char/agp/intel-agp.c b/drivers/char/agp/intel-agp.c
> index c771418..4373adb 100644
> --- a/drivers/char/agp/intel-agp.c
> +++ b/drivers/char/agp/intel-agp.c
> @@ -633,13 +633,15 @@ static void intel_i830_init_gtt_entries(void)
> break;
> }
> }
> - if (gtt_entries > 0)
> + if (gtt_entries > 0) {
> dev_info(&agp_bridge->dev->dev, "detected %dK %s memory\n",
> gtt_entries / KB(1), local ? "local" : "stolen");
> - else
> + gtt_entries /= KB(4);
> + } else {
> dev_info(&agp_bridge->dev->dev,
> "no pre-allocated video memory detected\n");
> - gtt_entries /= KB(4);
> + gtt_entries = 0;
> + }
>
> intel_private.gtt_entries = gtt_entries;
> }
>