Hi Laurent,
Sorry for calling by alst name. You 1st last both names are totally
new to me. Are these french names?
I understand your explanation. I was worried about code getting
misplaced due to automatic merges.
--
Thanks Regards,
Nitin
Open Source Technology Center, Intel Corporation
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On Wed, 2007-09-26 at 14:51 -0700, Laurent Vivier wrote:
Kamble, Nitin A wrote:
Hi Vivier, Avi,
Hi Nitin,
(BTW, my first name is Laurent)
In order to debug faulures in my tree, I was looking at the
saved_eip
changes coming from your commit. I did not understand the use of
saved_eip properly. like why is it used in the emulation of the pop
instruction. Can you please help me understand it's usage?
in emulate_instruction(), we decode instructions and copy vcpu
registers
to ctxt (in x86_decode_insn()), then we really emulate the instruction
(in x86_emulate_insn()).
In x86_emulate_insn(), if we have a REP prefix, we decrement ECX and
set
EIP to next instruction, then we try to emulate the instruction.
If the emulation fails (because this is a MMIO for instance) we have
to
restore the initial values of ECX and EIP because we will re-enter in
x86_emulate_insn() once the IO has been managed by Qemu and thus ECX
is
decremented again and EIP set to next instruction again.
And you are right: _we_don't_have_to_do_that_for_the_pop_instruction_,
it's a mistake because the REP prefix hasn't been processed at this
level, it is managed (ECX and EIP are modified) later.
So, you can remove from pop_instruction:
1383 if (c-rep_prefix) {
1384 c-regs[VCPU_REGS_RCX] =
saved_rcx;
1385 c-eip = saved_eip;
1386 }
Sorry for the inconvenience,
Laurent
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