On Tue, Jan 22, 2013 at 9:33 PM, Olivier DANET odanet@caramail.com wrote:
The SparcV8 standard states, page 134 : "If any of the three instructions after a write state register instruction reads any field that was changed by the original write state register instruction, the contents of that field read by that instruction are undefined." The restore instruction depends on the %WIM register, three NOPs must be inserted.
Please put the SoB here.
diff a/openbios-devel/arch/sparc32/wuf.S b/openbios-devel/arch/sparc32/wuf.S --- a/openbios-devel/arch/sparc32/wuf.S +++ b/openbios-devel/arch/sparc32/wuf.S @@ -121,7 +121,7 @@ fnwin_patch1: srl %t_wim, 7, %twin_tmp2 fnwin_patch2: and %twin_tmp1, 0xff, %twin_tmp1
wr %twin_tmp1, 0x0, %wim /* Make window 'I' invalid */
- WRITE_PAUSE
As you cite, this is needed on real HW. QEMU does not need it since internal pipelines are not modeled. Perhaps this (or the definition of WRITE_PAUSE) should be surrounded by #ifndef CONFIG_QEMU #endif
Anyway, TCG optimizes the nops away so it doesn't matter.
restore %g0, %g0, %g0 /* Restore to window 'O' */ /* Trapped from kernel, we trust that the kernel does notSigned-off-by: Olivier DANET odanet@caramail.com