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From: Juan Quintela <quintela@redhat.com>
In-Reply-To: <20180723123305.24792-4-peterx@redhat.com> (Peter Xu's message of
	"Mon, 23 Jul 2018 20:33:04 +0800")
References: <20180723123305.24792-1-peterx@redhat.com>
	<20180723123305.24792-4-peterx@redhat.com>
Reply-To: quintela@redhat.com
Date: Tue, 24 Jul 2018 11:23:38 +0200
Message-ID: <8736w9gf6t.fsf@secure.mitica>
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Subject: Re: [Qemu-devel] [PATCH for-3.0 3/4] tests: only update last_byte
 when at the edge
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To: Peter Xu <peterx@redhat.com>
Cc: qemu-devel@nongnu.org, "Dr . David Alan Gilbert" <dgilbert@redhat.com>

Peter Xu <peterx@redhat.com> wrote:
> The only possible change of last_byte is when it reaches the edge.
> Setting it every time might let last_byte contain an invalid data when
> memory corruption is detected, then the check of the next byte will be
> incorrect.  For example, a single page corruption at address 0x14ad000
> will also lead to a "fake" corruption at 0x14ae000:
>
>   Memory content inconsistency at 14ad000 first_byte = 44 last_byte = 44 current = ef hit_edge = 0
>   Memory content inconsistency at 14ae000 first_byte = 44 last_byte = ef current = 44 hit_edge = 0
>
> After the patch, it'll only report the corrputed page:
>
>   Memory content inconsistency at 14ad000 first_byte = 44 last_byte = 44 current = ef hit_edge = 0
>
> Signed-off-by: Peter Xu <peterx@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

Good catch.  I was having this problem in the past, but never
investigated the problem so far.