[Qemu-ppc] [PATCH] target/ppc: extend eieio for POWER9

[Cédric Le Goater]

POWER9 introduced a new variant of the eieio instruction using bit 6
as a hint to tell the CPU it is a store-forwarding barrier.

The usage of this eieio extension was recently added in Linux 4.17
which activated the "support for a store forwarding barrier at kernel
entry/exit".

Unfortunately, it is not possible to insert this new eieio instruction
without considerable change in ppc_tr_translate_insn(). So instead we
loosen the QEMU eieio instruction mask. The gen_eieio() helper is
modified to test for bit6 and a custom instruction flag to catch
invalid eieio opcodes on non-POWER9 CPUs.

Signed-off-by: Cédric Le Goater <address@hidden>
---
 target/ppc/cpu.h                |  5 ++++-
 target/ppc/translate.c          | 19 +++++++++++++++++--
 target/ppc/translate_init.inc.c |  3 ++-
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
index 0247c1f04c37..021c9b2f10d1 100644
--- a/target/ppc/cpu.h
+++ b/target/ppc/cpu.h
@@ -2206,6 +2206,9 @@ enum {
     /* POWER ISA 3.0                                                         */
     PPC2_ISA300        = 0x0000000000080000ULL,
 
+    /* POWER ISA 3.0 eieio variants                                          */
+    PPC2_MEM_EIEIO2    = 0x0000000000100000ULL,
+
 #define PPC_TCG_INSNS2 (PPC2_BOOKE206 | PPC2_VSX | PPC2_PRCNTL | PPC2_DBRX | \
                         PPC2_ISA205 | PPC2_VSX207 | PPC2_PERM_ISA206 | \
                         PPC2_DIVE_ISA206 | PPC2_ATOMIC_ISA206 | \
@@ -2213,7 +2216,7 @@ enum {
                         PPC2_BCTAR_ISA207 | PPC2_LSQ_ISA207 | \
                         PPC2_ALTIVEC_207 | PPC2_ISA207S | PPC2_DFP | \
                         PPC2_FP_CVT_S64 | PPC2_TM | PPC2_PM_ISA206 | \
-                        PPC2_ISA300)
+                        PPC2_ISA300 | PPC2_MEM_EIEIO2)
 };
 
 /*****************************************************************************/
diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index 8ba8f67dc513..a73ef02aef1d 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -2967,7 +2967,22 @@ static void gen_stswx(DisasContext *ctx)
 /* eieio */
 static void gen_eieio(DisasContext *ctx)
 {
-    tcg_gen_mb(TCG_MO_LD_ST | TCG_BAR_SC);
+    TCGBar bar = TCG_MO_LD_ST;
+
+    /*
+     * POWER9 has a eieio instruction variant using bit 6 as a hint to
+     * tell the CPU it is a store-forwarding barrier.
+     */
+    if (ctx->opcode & 0x2000000) {
+        if (!(ctx->insns_flags2 & PPC2_MEM_EIEIO2)) {
+            qemu_log_mask(LOG_GUEST_ERROR, "invalid eieio using bit 6 at @"
+                          TARGET_FMT_lx "\n", ctx->base.pc_next - 4);
+            return;
+        }
+        bar = TCG_MO_ST_LD;
+    }
+
+    tcg_gen_mb(bar | TCG_BAR_SC);
 }
 
 #if !defined(CONFIG_USER_ONLY)
@@ -6483,7 +6498,7 @@ GEN_HANDLER(lswi, 0x1F, 0x15, 0x12, 0x00000001, 
PPC_STRING),
 GEN_HANDLER(lswx, 0x1F, 0x15, 0x10, 0x00000001, PPC_STRING),
 GEN_HANDLER(stswi, 0x1F, 0x15, 0x16, 0x00000001, PPC_STRING),
 GEN_HANDLER(stswx, 0x1F, 0x15, 0x14, 0x00000001, PPC_STRING),
-GEN_HANDLER(eieio, 0x1F, 0x16, 0x1A, 0x03FFF801, PPC_MEM_EIEIO),
+GEN_HANDLER(eieio, 0x1F, 0x16, 0x1A, 0x01FFF801, PPC_MEM_EIEIO),
 GEN_HANDLER(isync, 0x13, 0x16, 0x04, 0x03FFF801, PPC_MEM),
 GEN_HANDLER_E(lbarx, 0x1F, 0x14, 0x01, 0, PPC_NONE, PPC2_ATOMIC_ISA206),
 GEN_HANDLER_E(lharx, 0x1F, 0x14, 0x03, 0, PPC_NONE, PPC2_ATOMIC_ISA206),
diff --git a/target/ppc/translate_init.inc.c b/target/ppc/translate_init.inc.c
index 1a89017ddea8..6b70f6dc5a2c 100644
--- a/target/ppc/translate_init.inc.c
+++ b/target/ppc/translate_init.inc.c
@@ -8847,7 +8847,8 @@ POWERPC_FAMILY(POWER9)(ObjectClass *oc, void *data)
                         PPC2_FP_TST_ISA206 | PPC2_BCTAR_ISA207 |
                         PPC2_LSQ_ISA207 | PPC2_ALTIVEC_207 |
                         PPC2_ISA205 | PPC2_ISA207S | PPC2_FP_CVT_S64 |
-                        PPC2_TM | PPC2_PM_ISA206 | PPC2_ISA300 | PPC2_PRCNTL;
+                        PPC2_TM | PPC2_PM_ISA206 | PPC2_ISA300 | PPC2_PRCNTL |
+                        PPC2_MEM_EIEIO2;
     pcc->msr_mask = (1ull << MSR_SF) |
                     (1ull << MSR_TM) |
                     (1ull << MSR_VR) |
-- 
2.13.6