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target-ppc: gen_pause for instructions: yield, mdoio, mdoom, miso 

Call gen_pause for all "or rx,rx,rx" encodings other nop.  This
provides a reasonable implementation for yield, and a better
approximation for mdoio, mdoom, and miso.  The choice to pause for all
encodings !=0 leverages the PowerISA admonition that the reserved
encodings might change program priority, providing a slight "future
proofing".

Signed-off-by: Aaron Larson <alarson@ddci.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Aaron Larson 2016-06-24 13:18:28 -07:00 committed by David Gibson
parent 27f2458245
commit 9e196938aa
1 changed files with 9 additions and 8 deletions
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17
target-ppc/translate.c
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@ -1471,7 +1471,7 @@ static void gen_or(DisasContext *ctx)
} else if (unlikely(Rc(ctx->opcode) != 0)) {
gen_set_Rc0(ctx, cpu_gpr[rs]);
#if defined(TARGET_PPC64)
} else {
} else if (rs != 0) { /* 0 is nop */
int prio = 0;
switch (rs) {
@ -1514,7 +1514,6 @@ static void gen_or(DisasContext *ctx)
break;
#endif
default:
/* nop */
break;
}
if (prio) {
@ -1524,13 +1523,15 @@ static void gen_or(DisasContext *ctx)
tcg_gen_ori_tl(t0, t0, ((uint64_t)prio) << 50);
gen_store_spr(SPR_PPR, t0);
tcg_temp_free(t0);
/* Pause us out of TCG otherwise spin loops with smt_low
* eat too much CPU and the kernel hangs
*/
#if !defined(CONFIG_USER_ONLY)
gen_pause(ctx);
#endif
}
#if !defined(CONFIG_USER_ONLY)
/* Pause out of TCG otherwise spin loops with smt_low eat too much
* CPU and the kernel hangs. This applies to all encodings other
* than no-op, e.g., miso(rs=26), yield(27), mdoio(29), mdoom(30),
* and all currently undefined.
*/
gen_pause(ctx);
#endif
#endif
}
}