On 11/03/2016 10:21 AM, Laurent Vivier wrote:
Le 03/11/2016 à 17:18, Paolo Bonzini a écrit :
Well, tas_test "runs without error with this change", I suppose it fails
before? In other words, is this patch enough to run multithreaded sh4
programs with qemu-user?
It should,:the problem was reported by Adrian (cc:) while compiling ghc
in qemu-sh4, but I have just tested the functionality with the softmmu
version, not the atomicity.
Adrian, could you test this patch?
It's a start, but sh4 has an interesting scheme to implement atomic sequences
via special values in the stack pointer. E.g. xchg is
mova 1f, r0
mov sp, r1
mov #(0f-1f), sp
0: mov.l mem, out
mov.l in, mem
1: mov r1, sp
which is only atomic if you've got a UP kernel and have code in your interrupt
entry point that recognizes the small negative value in SP to reset the PC as
necessary.
For SH4A, there are proper load-locked/store-condition insns, but prior to that
TAS was the only truly atomic insn.
r~
