Re: [Qemu-arm] [PATCH 08/11] tcg/aarch64: Make direct jump patching thread-safe

[Richard Henderson]

On 04/20/2016 07:01 AM, Alex Bennée wrote:
> Sergey Fedorov <address@hidden> writes:
>
> > From: Sergey Fedorov <address@hidden>
> >
> > Ensure direct jump patching in AArch64 is atomic by using
> > atomic_read()/atomic_set() for code patching.
> >
> > Signed-off-by: Sergey Fedorov <address@hidden>
> > Signed-off-by: Sergey Fedorov <address@hidden>
> > ---
> >   tcg/aarch64/tcg-target.inc.c | 14 +++++++++++++-
> >   1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/tcg/aarch64/tcg-target.inc.c b/tcg/aarch64/tcg-target.inc.c
> > index 0ed10a974121..15fdebec921f 100644
> > --- a/tcg/aarch64/tcg-target.inc.c
> > +++ b/tcg/aarch64/tcg-target.inc.c
> > @@ -73,6 +73,18 @@ static inline void reloc_pc26(tcg_insn_unit *code_ptr, 
> > tcg_insn_unit *target)
> >       *code_ptr = deposit32(*code_ptr, 0, 26, offset);
> >   }
> >
> > +static inline void reloc_pc26_atomic(tcg_insn_unit *code_ptr,
> > +                                     tcg_insn_unit *target)
> > +{
> > +    ptrdiff_t offset = target - code_ptr;
> > +    tcg_insn_unit insn;
> > +    assert(offset == sextract64(offset, 0, 26));
> > +    /* read instruction, mask away previous PC_REL26 parameter contents,
> > +       set the proper offset, then write back the instruction. */
>
> This comment could be moved from here and reloc_pc26 and made common for
> the two following functions.

There's a significant amount of cleanup that ought to happen here, now that 
we're not re-translating TBs.  I don't know if Sergey should be gated on that.


r~