Re: [Qemu-devel] [PATCH v3 00/15] target-sparc improvements

[Richard Henderson]

On 10/31/2016 09:40 AM, Artyom Tarasenko wrote:
> >   * The "Remove asi helper code handled inline" patch retains the code within
> >     ldda to handle asis that must be handled out of line.  This fixes the
> >     FreeBSD 10.3 boot problem.  While the UA2007 spec (and thus sun4v?) doesn't
> >     allow for such, it would seem that US2 hardware does.
>
> What ASI was failing? It may still be a part of sun4v CPUs if it's
> described in UST1/UST2 supplements.

0x00000000c08e5680:  clr  %g4
0x00000000c08e5684:  mov  1, %g1
0x00000000c08e5688:  sllx  %g1, 0x24, %o5
0x00000000c08e568c:  mov  -1, %g1
0x00000000c08e5690:  sllx  %g1, 0x23, %g1
0x00000000c08e5694:  xor  %g1, -128, %o4
0x00000000c08e5698:  ldda  [ %g4 ] #ASI_IC_TAG, %g0     ****
0x00000000c08e569c:  mov  %g1, %g2
0x00000000c08e56a0:  and  %g1, %o5, %g1
0x00000000c08e56a4:  brz,a   %g1, 0xc08e56dc

So indeed it would appear that FreeBSD does in fact want the half of the result 
that would get stored into %g1.  As far as I can see they could have achieved 
the same result with

        ldxa    [%g4] #ASI_IC_TAG, %g1
        srl     %g1, 0, %g1

to stay within the nominal spec.


r~