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Re: [Xen-devel] [PATCH v2] xen/arm: Fix the issue in cmp_mmio_handler used in find_mmio_handler

Hi Bhupinder,

On 09/29/2017 01:33 AM, Bhupinder Thakur wrote:
This function returns true/false based on whether the key value

Technically, this function returns 3 values: -1/0/1. The commit message should be updated to reflect that.

is in the range (start, start+size). However, it should check against
(start, start+size-1) because start+size falls outside the range.

This resulted in returning a wrong mmio_handler for a given mmio address which
happened to be start+size.

This bug was introduced when the mmio region search was switched from
linear search to binary search in the following commit:

8047e09 "xen/arm: io: Use binary search for mmio handler lookup".

This change may have to be back-ported to 4.8 also.

FIY, this does not need to be in the commit message. You could add after "---". When committed, it will get removed.

Signed-off-by: Bhupinder Thakur <bhupinder.thakur@xxxxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>

  xen/arch/arm/io.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
index e216128..c748d8f 100644
--- a/xen/arch/arm/io.c
+++ b/xen/arch/arm/io.c
@@ -79,7 +79,7 @@ static int cmp_mmio_handler(const void *key, const void *elem)
      if ( handler0->addr < handler1->addr )
          return -1;
- if ( handler0->addr > (handler1->addr + handler1->size) )
+    if ( handler0->addr >= (handler1->addr + handler1->size) )
          return 1;
return 0;


Julien Grall

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