An Event-Based Branch (EBB) allows applications to change the NIA when a
event-based exception occurs. Event-based exceptions are enabled by
setting the Branch Event Status and Control Register (BESCR). If the
event-based exception is enabled when the exception occurs, an EBB
happens.
The following operations happens during an EBB:
- Global Enable (GE) bit of BESCR is set to 0;
- bits 0-61 of the Event-Based Branch Return Register (EBBRR) are set
to the the effective address of the NIA that would have executed if the EBB
didn't happen;
- Instruction fetch and execution will continue in the effective address
contained in the Event-Based Branch Handler Register (EBBHR).
The EBB Handler will process the event and then execute the Return From
Event-Based Branch (rfebb) instruction. rfebb sets BESCR_GE and then
redirects execution to the address pointed in EBBRR. This process is
described in the PowerISA v3.1, Book II, Chapter 6 [1].
This patch implements the rfebb instruction. Descriptions of all
relevant BESCR bits are also added - this patch is only using BESCR_GE,
but the next patches will use the remaining bits.
[1] https://wiki.raptorcs.com/w/images/f/f5/PowerISA_public.v3.1.pdf
Signed-off-by: Daniel Henrique Barboza <danielhb...@gmail.com>
---
target/ppc/cpu.h | 13 ++++++++++
target/ppc/excp_helper.c | 31 ++++++++++++++++++++++++
target/ppc/helper.h | 1 +
target/ppc/insn32.decode | 5 ++++
target/ppc/translate.c | 2 ++
target/ppc/translate/branch-impl.c.inc | 33 ++++++++++++++++++++++++++
6 files changed, 85 insertions(+)
create mode 100644 target/ppc/translate/branch-impl.c.inc
diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
index 93f4a46827..26624508fa 100644
--- a/target/ppc/cpu.h
+++ b/target/ppc/cpu.h
@@ -368,6 +368,19 @@ typedef struct ppc_v3_pate_t {
/* PMU uses CTRL_RUN to sample PM_RUN_INST_CMPL */
#define CTRL_RUN PPC_BIT(63)
+/* EBB/BESCR bits */
+/* Global Enable */
+#define BESCR_GE PPC_BIT(0)
+/* External Event-based Exception Enable */
+#define BESCR_EE PPC_BIT(30)
+/* Performance Monitor Event-based Exception Enable */
+#define BESCR_PME PPC_BIT(31)
+/* External Event-based Exception Occurred */
+#define BESCR_EEO PPC_BIT(62)
+/* Performance Monitor Event-based Exception Occurred */
+#define BESCR_PMEO PPC_BIT(63)
+#define BESCR_INVALID PPC_BITMASK(32, 33)
+
/* LPCR bits */
#define LPCR_VPM0 PPC_BIT(0)
#define LPCR_VPM1 PPC_BIT(1)
diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
index 7b6ac16eef..22f9835383 100644
--- a/target/ppc/excp_helper.c
+++ b/target/ppc/excp_helper.c
@@ -1281,6 +1281,37 @@ void helper_hrfid(CPUPPCState *env)
}
#endif
+#if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY)
+void helper_rfebb(CPUPPCState *env, target_ulong s)
+{
+ target_ulong msr = env->msr;
+
+ /*
+ * Handling of BESCR bits 32:33 according to PowerISA v3.1:
+ *
+ * "If BESCR 32:33 != 0b00 the instruction is treated as if
+ * the instruction form were invalid."
+ */
+ if (env->spr[SPR_BESCR] & BESCR_INVALID) {
+ raise_exception_err(env, POWERPC_EXCP_PROGRAM,
+ POWERPC_EXCP_INVAL | POWERPC_EXCP_INVAL_INVAL);
+ }
+
+ env->nip = env->spr[SPR_EBBRR];
+
+ /* Switching to 32-bit ? Crop the nip */
+ if (!msr_is_64bit(env, msr)) {
+ env->nip = (uint32_t)env->spr[SPR_EBBRR];
+ }
+
+ if (s) {
+ env->spr[SPR_BESCR] |= BESCR_GE;
+ } else {
+ env->spr[SPR_BESCR] &= ~BESCR_GE;
+ }
+}
+#endif
+
/*****************************************************************************/
/* Embedded PowerPC specific helpers */
void helper_40x_rfci(CPUPPCState *env)
diff --git a/target/ppc/helper.h b/target/ppc/helper.h
index 47dbbe6da1..91a86992a5 100644
--- a/target/ppc/helper.h
+++ b/target/ppc/helper.h
@@ -18,6 +18,7 @@ DEF_HELPER_2(pminsn, void, env, i32)
DEF_HELPER_1(rfid, void, env)
DEF_HELPER_1(rfscv, void, env)
DEF_HELPER_1(hrfid, void, env)
+DEF_HELPER_2(rfebb, void, env, tl)
DEF_HELPER_2(store_lpcr, void, env, tl)
DEF_HELPER_2(store_pcr, void, env, tl)
DEF_HELPER_2(store_mmcr0, void, env, tl)
diff --git a/target/ppc/insn32.decode b/target/ppc/insn32.decode
index 9fd8d6b817..deb7374ea4 100644
--- a/target/ppc/insn32.decode
+++ b/target/ppc/insn32.decode
@@ -124,3 +124,8 @@ SETNBCR 011111 ..... ..... ----- 0111100000 -
@X_bi
## Vector Bit Manipulation Instruction
VCFUGED 000100 ..... ..... ..... 10101001101 @VX
+
+### rfebb
+&XL_s s:uint8_t
+@XL_s ......-------------- s:1 .......... - &XL_s
+RFEBB 010011-------------- . 0010010010 - @XL_s
diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index 866b1d2b34..7a3104ecf9 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -7636,6 +7636,8 @@ static int times_4(DisasContext *ctx, int x)
#include "translate/spe-impl.c.inc"
+#include "translate/branch-impl.c.inc"
+
/* Handles lfdp, lxsd, lxssp */
static void gen_dform39(DisasContext *ctx)
{
diff --git a/target/ppc/translate/branch-impl.c.inc
b/target/ppc/translate/branch-impl.c.inc
new file mode 100644
index 0000000000..9c991d9abb
--- /dev/null
+++ b/target/ppc/translate/branch-impl.c.inc
@@ -0,0 +1,33 @@
+/*
+ * Power ISA decode for branch instructions
+ *
+ * Copyright IBM Corp. 2021
+ *
+ * Authors:
+ * Daniel Henrique Barboza <danielhb...@gmail.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY)
+
+static bool trans_RFEBB(DisasContext *ctx, arg_RFEBB *arg)
