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Re: [Qemu-devel] [PATCH 4/5] tcg: reorder removal from lists in tb_phys_

From: Paolo Bonzini
Subject: Re: [Qemu-devel] [PATCH 4/5] tcg: reorder removal from lists in tb_phys_invalidate
Date: Mon, 28 Mar 2016 22:58:08 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0

On 28/03/2016 20:42, Sergey Fedorov wrote:
> On 17/03/16 16:46, address@hidden wrote:
>> First the translation block is invalidated, for which a simple write
>> to tb->pc is enough.  This means that cpu-exec will not pick up anymore
>> the block, though it may still execute it through chained jumps.  This
>> also replaces the NULLing out of the pointer in the CPUs' local cache.
> Although, using 'tb->pc' to mark a TB as invalid is probably not such a
> good idea. There may be some cases when PC could become equal to -1. For
> example, ARMv6-M uses PC >= 0xFFFFFFF0 to perform exception return. So
> we'd better introduce a separate 'tb->valid' or 'tb->invalid' flag.

It is also possible to use tb->flags for that.  I suspect that all-ones
tb flags is never valid, but it could also be a #define.


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