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Re: [Qemu-devel] [PATCH 21/26] target-xtensa: implement unaligned except
From: |
Max Filippov |
Subject: |
Re: [Qemu-devel] [PATCH 21/26] target-xtensa: implement unaligned exception option |
Date: |
Mon, 23 May 2011 00:12:34 +0400 |
User-agent: |
KMail/1.13.6 (Linux/2.6.34.8-68.fc13.x86_64; KDE/4.5.5; x86_64; ; ) |
> > There are three alignment possibilities for xtensa: no unaligned
> > exception, unaligned exception and hardware alignment. In the first
> > case unaligned access silently goes to aligned address. It looks like
> > it cannot be done via do_unaligned_access, can it? In the third case
> > most unaligned accesses are handled transparently by the hardware.
> > But e.g. unaligned access by multiprocessor synchronization
> > instructions still cause alignment exception. Do I need to implement
> > a different alignment checking mechanism for those unhandled cases?
>
> Case (1), silently going to an aligned address, should be handled
> inside the translator by masking the address before the load. See
> the ARM and Alpha targets for examples.
This is what gen_load_store_alignment does.
> Case (2) and (3) are both handled by using ALIGNED_ONLY. All you
> need to do to handle (3) is *not* throw an exception from the
> do_unaligned_access function. See how the code is structured
> inside softmmu_template.h.
>
> As for sync insns... You may need to handle it all out-of-line
> and check for alignment there.
This is also done by gen_load_store_alignment.
Does it really worth copying part of this logic to do_unaligned_access just to
use ALIGNED_ONLY framework?
Thanks.
-- Max
- Re: [Qemu-devel] [PATCH 19/26] target-xtensa: implement loop option, (continued)
[Qemu-devel] [PATCH 20/26] target-xtensa: implement extended L32R, Max Filippov, 2011/05/17
[Qemu-devel] [PATCH 21/26] target-xtensa: implement unaligned exception option, Max Filippov, 2011/05/17
- Re: [Qemu-devel] [PATCH 21/26] target-xtensa: implement unaligned exception option, Richard Henderson, 2011/05/19
- Re: [Qemu-devel] [PATCH 21/26] target-xtensa: implement unaligned exception option, Max Filippov, 2011/05/22
- Re: [Qemu-devel] [PATCH 21/26] target-xtensa: implement unaligned exception option, Richard Henderson, 2011/05/22
- Re: [Qemu-devel] [PATCH 21/26] target-xtensa: implement unaligned exception option,
Max Filippov <=
- Re: [Qemu-devel] [PATCH 21/26] target-xtensa: implement unaligned exception option, Richard Henderson, 2011/05/23
- Re: [Qemu-devel] [PATCH 21/26] target-xtensa: implement unaligned exception option, Max Filippov, 2011/05/23
- Re: [Qemu-devel] [PATCH 21/26] target-xtensa: implement unaligned exception option, Richard Henderson, 2011/05/24
[Qemu-devel] [PATCH 22/26] target-xtensa: implement SIMCALL, Max Filippov, 2011/05/17
[Qemu-devel] [PATCH 23/26] target-xtensa: implement interrupt option, Max Filippov, 2011/05/17