[PATCH v3 01/15] target/ppc: add user read functions for MMCR0 and MMCR2

[Daniel Henrique Barboza <danielhb413@gmail.com>]

From: Gustavo Romero <gromero@linux.ibm.com>

We're going to add PMU support for TCG PPC64 chips, based on IBM POWER8+
emulation and following PowerISA v3.1.

Let's start by handling the user read of UMMCR0 and UMMCR2. According to
PowerISA 3.1 these registers omit some of its bits from userspace.

CC: Gustavo Romero <gustavo.romero@linaro.org>
Signed-off-by: Gustavo Romero <gromero@linux.ibm.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
---
 target/ppc/cpu.h       | 10 ++++++++++
 target/ppc/cpu_init.c  |  4 ++--
 target/ppc/spr_tcg.h   |  2 ++
 target/ppc/translate.c | 37 +++++++++++++++++++++++++++++++++++++
 4 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
index 500205229c..f68bb8d8aa 100644
--- a/target/ppc/cpu.h
+++ b/target/ppc/cpu.h
@@ -342,6 +342,16 @@ typedef struct ppc_v3_pate_t {
 #define MSR_RI   1  /* Recoverable interrupt                        1        */
 #define MSR_LE   0  /* Little-endian mode                           1 hflags */
 
+/* PMU bits */
+#define MMCR0_FC    PPC_BIT(32)         /* Freeze Counters  */
+#define MMCR0_PMAO  PPC_BIT(56)         /* Perf Monitor Alert Ocurred */
+#define MMCR0_PMAE  PPC_BIT(37)         /* Perf Monitor Alert Enable */
+#define MMCR0_EBE   PPC_BIT(43)         /* Perf Monitor EBB Enable */
+#define MMCR0_FCECE PPC_BIT(38)         /* FC on Enabled Cond or Event */
+#define MMCR0_PMCC  PPC_BITMASK(44, 45) /* PMC Control */
+/* MMCR0 userspace r/w mask */
+#define MMCR0_UREG_MASK (MMCR0_FC | MMCR0_PMAO | MMCR0_PMAE)
+
 /* LPCR bits */
 #define LPCR_VPM0         PPC_BIT(0)
 #define LPCR_VPM1         PPC_BIT(1)
diff --git a/target/ppc/cpu_init.c b/target/ppc/cpu_init.c
index ad7abc6041..9efc6c2d87 100644
--- a/target/ppc/cpu_init.c
+++ b/target/ppc/cpu_init.c
@@ -6867,7 +6867,7 @@ static void register_book3s_pmu_sup_sprs(CPUPPCState *env)
 static void register_book3s_pmu_user_sprs(CPUPPCState *env)
 {
     spr_register(env, SPR_POWER_UMMCR0, "UMMCR0",
-                 &spr_read_ureg, SPR_NOACCESS,
+                 &spr_read_MMCR0_ureg, SPR_NOACCESS,
                  &spr_read_ureg, &spr_write_ureg,
                  0x00000000);
     spr_register(env, SPR_POWER_UMMCR1, "UMMCR1",
@@ -6975,7 +6975,7 @@ static void register_power8_pmu_sup_sprs(CPUPPCState *env)
 static void register_power8_pmu_user_sprs(CPUPPCState *env)
 {
     spr_register(env, SPR_POWER_UMMCR2, "UMMCR2",
-                 &spr_read_ureg, SPR_NOACCESS,
+                 &spr_read_MMCR2_ureg, SPR_NOACCESS,
                  &spr_read_ureg, &spr_write_ureg,
                  0x00000000);
     spr_register(env, SPR_POWER_USIER, "USIER",
diff --git a/target/ppc/spr_tcg.h b/target/ppc/spr_tcg.h
index 0be5f347d5..30cb6c3fdc 100644
--- a/target/ppc/spr_tcg.h
+++ b/target/ppc/spr_tcg.h
@@ -32,6 +32,8 @@ void spr_write_lr(DisasContext *ctx, int sprn, int gprn);
 void spr_read_ctr(DisasContext *ctx, int gprn, int sprn);
 void spr_write_ctr(DisasContext *ctx, int sprn, int gprn);
 void spr_read_ureg(DisasContext *ctx, int gprn, int sprn);
+void spr_read_MMCR0_ureg(DisasContext *ctx, int gprn, int sprn);
+void spr_read_MMCR2_ureg(DisasContext *ctx, int gprn, int sprn);
 void spr_read_tbl(DisasContext *ctx, int gprn, int sprn);
 void spr_read_tbu(DisasContext *ctx, int gprn, int sprn);
 void spr_read_atbl(DisasContext *ctx, int gprn, int sprn);
diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index 171b216e17..b2ead144d1 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -519,6 +519,43 @@ void spr_read_ureg(DisasContext *ctx, int gprn, int sprn)
     gen_load_spr(cpu_gpr[gprn], sprn + 0x10);
 }
 
+void spr_read_MMCR0_ureg(DisasContext *ctx, int gprn, int sprn)
+{
+    TCGv t0 = tcg_temp_new();
+
+    /*
+     * Filter out all bits but FC, PMAO, and PMAE, according
+     * to ISA v3.1, in 10.4.4 Monitor Mode Control Register 0,
+     * fourth paragraph.
+     */
+    gen_load_spr(t0, SPR_POWER_MMCR0);
+    tcg_gen_andi_tl(t0, t0, MMCR0_UREG_MASK);
+    tcg_gen_mov_tl(cpu_gpr[gprn], t0);
+
+    tcg_temp_free(t0);
+}
+
+void spr_read_MMCR2_ureg(DisasContext *ctx, int gprn, int sprn)
+{
+    TCGv t0 = tcg_temp_new();
+
+    /*
+     * On read, filter out all bits that are not FCnP0 bits.
+     * When MMCR0[PMCC] is set to 0b10 or 0b11, providing
+     * problem state programs read/write access to MMCR2,
+     * only the FCnP0 bits can be accessed. All other bits are
+     * not changed when mtspr is executed in problem state, and
+     * all other bits return 0s when mfspr is executed in problem
+     * state, according to ISA v3.1, section 10.4.6 Monitor Mode
+     * Control Register 2, p. 1316, third paragraph.
+     */
+    gen_load_spr(t0, SPR_POWER_MMCR2);
+    tcg_gen_andi_tl(t0, t0, 0x4020100804020000UL);
+    tcg_gen_mov_tl(cpu_gpr[gprn], t0);
+
+    tcg_temp_free(t0);
+}
+
 #if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY)
 void spr_write_ureg(DisasContext *ctx, int sprn, int gprn)
 {
-- 
2.31.1