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From: Blue Swirl <blauwirbel@gmail.com>
Date: Thu, 7 Oct 2010 17:36:36 +0000
Message-ID: <AANLkTikTXnq7N+--tmgZwnimmw31Nv2g97T5KqVWMOQ8@mail.gmail.com>
Subject: Re: [Qemu-devel] Re: [PATCH 09/11] i386: avoid a write only variable
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To: malc <av1474@comtv.ru>
Cc: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel <qemu-devel@nongnu.org>

On Thu, Oct 7, 2010 at 8:27 AM, malc <av1474@comtv.ru> wrote:
> On Thu, 7 Oct 2010, Paolo Bonzini wrote:
>
>> On 10/06/2010 11:34 PM, Blue Swirl wrote:
>> > Compiling with GCC 4.6.0 20100925 produced warnings:
>> > /src/qemu/target-i386/op_helper.c: In function 'switch_tss':
>> > /src/qemu/target-i386/op_helper.c:283:53: error: variable 'new_trap'
>> > set but not used [-Werror=3Dunused-but-set-variable]
>> >
>> > Fix by deleting the variable.
>>
>> Again, this warning tells us the emulation is incorrect, so it's wrong t=
o
>> remove it.
>>
>
> http://support.amd.com/us/Processor_TechDocs/24593.pdf
>
> 12.2.5
> T (Trap) Bit--=E2=96=A0Bit 0 of byte 64h, static field. This bit, when se=
t to1,
> causes a debug exception (#DB) to occur on a task switch. See "Beakpoint
> Instruction (INT3)" page 340 for additional information.

Yes, I read that before making the patch. But page 340 didn't seem to
give any relevant information.