target/arm: Implement dummy versions of M-profile FP-related registers

The M-profile floating point support has three associated config
registers: FPCAR, FPCCR and FPDSCR. It also makes the registers
CPACR and NSACR have behaviour other than reads-as-zero.
Add support for all of these as simple reads-as-written registers.
We will hook up actual functionality later.

The main complexity here is handling the FPCCR register, which
has a mix of banked and unbanked bits.

Note that we don't share storage with the A-profile
cpu->cp15.nsacr and cpu->cp15.cpacr_el1, though the behaviour
is quite similar, for two reasons:
 * the M profile CPACR is banked between security states
 * it preserves the invariant that M profile uses no state
   inside the cp15 substruct

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190416125744.27770-4-peter.maydell@linaro.org

3 files changed, 55 insertions, 0 deletions

diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index bb9fdc6..be81e19 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -281,6 +281,11 @@ static void arm_cpu_reset(CPUState *s)
             env->v7m.ccr[M_REG_S] |= R_V7M_CCR_UNALIGN_TRP_MASK;
         }
 
+        if (arm_feature(env, ARM_FEATURE_VFP)) {
+            env->v7m.fpccr[M_REG_NS] = R_V7M_FPCCR_ASPEN_MASK;
+            env->v7m.fpccr[M_REG_S] = R_V7M_FPCCR_ASPEN_MASK |
+                R_V7M_FPCCR_LSPEN_MASK | R_V7M_FPCCR_S_MASK;
+        }
         /* Unlike A/R profile, M profile defines the reset LR value */
         env->regs[14] = 0xffffffff;
 
diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index f7f2f5a..67e4e95 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -533,6 +533,11 @@ typedef struct CPUARMState {
         uint32_t scr[M_REG_NUM_BANKS];
         uint32_t msplim[M_REG_NUM_BANKS];
         uint32_t psplim[M_REG_NUM_BANKS];
+        uint32_t fpcar[M_REG_NUM_BANKS];
+        uint32_t fpccr[M_REG_NUM_BANKS];
+        uint32_t fpdscr[M_REG_NUM_BANKS];
+        uint32_t cpacr[M_REG_NUM_BANKS];
+        uint32_t nsacr;
     } v7m;
 
     /* Information associated with an exception about to be taken:
@@ -1576,6 +1581,35 @@ FIELD(V7M_CSSELR, LEVEL, 1, 3)
  */
 FIELD(V7M_CSSELR, INDEX, 0, 4)
 
+/* v7M FPCCR bits */
+FIELD(V7M_FPCCR, LSPACT, 0, 1)
+FIELD(V7M_FPCCR, USER, 1, 1)
+FIELD(V7M_FPCCR, S, 2, 1)
+FIELD(V7M_FPCCR, THREAD, 3, 1)
+FIELD(V7M_FPCCR, HFRDY, 4, 1)
+FIELD(V7M_FPCCR, MMRDY, 5, 1)
+FIELD(V7M_FPCCR, BFRDY, 6, 1)
+FIELD(V7M_FPCCR, SFRDY, 7, 1)
+FIELD(V7M_FPCCR, MONRDY, 8, 1)
+FIELD(V7M_FPCCR, SPLIMVIOL, 9, 1)
+FIELD(V7M_FPCCR, UFRDY, 10, 1)
+FIELD(V7M_FPCCR, RES0, 11, 15)
+FIELD(V7M_FPCCR, TS, 26, 1)
+FIELD(V7M_FPCCR, CLRONRETS, 27, 1)
+FIELD(V7M_FPCCR, CLRONRET, 28, 1)
+FIELD(V7M_FPCCR, LSPENS, 29, 1)
+FIELD(V7M_FPCCR, LSPEN, 30, 1)
+FIELD(V7M_FPCCR, ASPEN, 31, 1)
+/* These bits are banked. Others are non-banked and live in the M_REG_S bank */
+#define R_V7M_FPCCR_BANKED_MASK                 \
+    (R_V7M_FPCCR_LSPACT_MASK |                  \
+     R_V7M_FPCCR_USER_MASK |                    \
+     R_V7M_FPCCR_THREAD_MASK |                  \
+     R_V7M_FPCCR_MMRDY_MASK |                   \
+     R_V7M_FPCCR_SPLIMVIOL_MASK |               \
+     R_V7M_FPCCR_UFRDY_MASK |                   \
+     R_V7M_FPCCR_ASPEN_MASK)
+
 /*
  * System register ID fields.
  */
diff --git a/target/arm/machine.c b/target/arm/machine.c
index b292549..09567d4 100644
--- a/target/arm/machine.c
+++ b/target/arm/machine.c
@@ -305,6 +305,21 @@ static const VMStateDescription vmstate_m_v8m = {
     }
 };
 
+static const VMStateDescription vmstate_m_fp = {
+    .name = "cpu/m/fp",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = vfp_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT32_ARRAY(env.v7m.fpcar, ARMCPU, M_REG_NUM_BANKS),
+        VMSTATE_UINT32_ARRAY(env.v7m.fpccr, ARMCPU, M_REG_NUM_BANKS),
+        VMSTATE_UINT32_ARRAY(env.v7m.fpdscr, ARMCPU, M_REG_NUM_BANKS),
+        VMSTATE_UINT32_ARRAY(env.v7m.cpacr, ARMCPU, M_REG_NUM_BANKS),
+        VMSTATE_UINT32(env.v7m.nsacr, ARMCPU),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static const VMStateDescription vmstate_m = {
     .name = "cpu/m",
     .version_id = 4,
@@ -330,6 +345,7 @@ static const VMStateDescription vmstate_m = {
         &vmstate_m_scr,
         &vmstate_m_other_sp,
         &vmstate_m_v8m,
+        &vmstate_m_fp,
         NULL
     }
 };