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Re: [Qemu-devel] [RFC] Tracing guest register usage


From: Richard Henderson
Subject: Re: [Qemu-devel] [RFC] Tracing guest register usage
Date: Wed, 5 Oct 2016 09:16:03 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0

On 10/05/2016 03:06 AM, Lluís Vilanova wrote:
Richard Henderson writes:

On 09/30/2016 08:13 AM, Lluís Vilanova wrote:
(2) an internal state change
to DisasContext, reflected in INDEX_op_insn_start, with no changes to any TCG
registers.  So you'll not actually be tracking eflags at all.

I don't follow what you mean. AFAIK INDEX_op_insn_start does not change the
guest eflags.

It sets cc_op, which affects how eflags is computed.

I see tcg_gen_insn_start() gets dc->cc_op as a second argument, but I really
don't see where it gets modified (I'm looking at tcg_gen_code() on the
INDEX_op_insn_start case).

The ultimate change is in restore_state_to_opc, via cpu_restore_state.


r~



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