For FEAT_NV2, a new system register VNCR_EL2 holds the base
address of the memory which nested-guest system register
accesses are redirected to. Implement this register.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Miguel Luis <miguel.luis@oracle.com>
---
 target/arm/cpu.h    |  3 +++
 target/arm/helper.c | 26 ++++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index d7a10fb4b61..0e48a1366bd 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -547,6 +547,9 @@ typedef struct CPUArchState {
         uint64_t gpccr_el3;
         uint64_t gptbr_el3;
         uint64_t mfar_el3;
+
+        /* NV2 register */
+        uint64_t vncr_el2;
     } cp15;
 
     struct {
diff --git a/target/arm/helper.c b/target/arm/helper.c
index e3e56539594..53bd6c85990 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -8131,6 +8131,28 @@ static const ARMCPRegInfo fgt_reginfo[] = {
       .access = PL2_RW, .accessfn = access_fgt,
       .fieldoffset = offsetof(CPUARMState, cp15.fgt_exec[FGTREG_HFGITR]) },
 };
+
+static void vncr_write(CPUARMState *env, const ARMCPRegInfo *ri,
+                       uint64_t value)
+{
+    /*
+     * Clear the RES0 bottom 12 bits; this means at runtime we can guarantee
+     * that VNCR_EL2 + offset is 64-bit aligned. We don't need to do anything
+     * about the RESS bits at the top -- we choose the "generate an EL2
+     * translation abort on use" CONSTRAINED UNPREDICTABLE option (i.e. let
+     * the ptw.c code detect the resulting invalid address).
+     */
+    env->cp15.vncr_el2 = value & ~0xfffULL;
+}
+
+static const ARMCPRegInfo nv2_reginfo[] = {
+    { .name = "VNCR_EL2", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 4, .crn = 2, .crm = 2, .opc2 = 0,
+      .access = PL2_RW,
+      .writefn = vncr_write,
+      .fieldoffset = offsetof(CPUARMState, cp15.vncr_el2) },
+};
+
 #endif /* TARGET_AARCH64 */
 
 static CPAccessResult access_predinv(CPUARMState *env, const ARMCPRegInfo *ri,
@@ -9614,6 +9636,10 @@ void register_cp_regs_for_features(ARMCPU *cpu)
             define_arm_cp_regs(cpu, rme_mte_reginfo);
         }
     }
+
+    if (cpu_isar_feature(aa64_nv2, cpu)) {
+        define_arm_cp_regs(cpu, nv2_reginfo);
+    }
 #endif
 
     if (cpu_isar_feature(any_predinv, cpu)) {
-- 
2.34.1