[Qemu-devel] [PATCH for-v3.1 3/3] target/arm: Correctly implement handling of HCR_EL2.{VI, VF}

[Peter Maydell <peter.maydell@linaro.org>]

In commit 8a0fc3a29fc2315325400 we tried to implement HCR_EL2.{VI,VF},
but we got it wrong and had to revert it.

In that commit we implemented them as simply tracking whether there
is a pending virtual IRQ or virtual FIQ. This is not correct -- these
bits cause a software-generated VIRQ/VFIQ, which is distinct from
whether there is a hardware-generated VIRQ/VFIQ caused by the
external interrupt controller. So we need to track separately
the HCR_EL2 bit state and the external virq/vfiq line state, and
OR the two together to get the actual pending VIRQ/VFIQ state.

Fixes: 8a0fc3a29fc2315325400c738f807d0d4ae0ab7f
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/internals.h | 18 ++++++++++++++++
 target/arm/cpu.c       | 48 +++++++++++++++++++++++++++++++++++++++++-
 target/arm/helper.c    | 20 ++++++++++++++++--
 3 files changed, 83 insertions(+), 3 deletions(-)

diff --git a/target/arm/internals.h b/target/arm/internals.h
index 6c2bb2deebd..a32d359dd03 100644
--- a/target/arm/internals.h
+++ b/target/arm/internals.h
@@ -871,4 +871,22 @@ static inline const char *aarch32_mode_name(uint32_t psr)
     return cpu_mode_names[psr & 0xf];
 }
 
+/**
+ * arm_cpu_update_virq: Update CPU_INTERRUPT_VIRQ bit in cs->interrupt_request
+ *
+ * Update the CPU_INTERRUPT_VIRQ bit in cs->interrupt_request, following
+ * a change to either the input VIRQ line from the GIC or the HCR_EL2.VI bit.
+ * Must be called with the iothread lock held.
+ */
+void arm_cpu_update_virq(ARMCPU *cpu);
+
+/**
+ * arm_cpu_update_vfiq: Update CPU_INTERRUPT_VFIQ bit in cs->interrupt_request
+ *
+ * Update the CPU_INTERRUPT_VFIQ bit in cs->interrupt_request, following
+ * a change to either the input VFIQ line from the GIC or the HCR_EL2.VF bit.
+ * Must be called with the iothread lock held.
+ */
+void arm_cpu_update_vfiq(ARMCPU *cpu);
+
 #endif
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 45c16ae90ba..6fbea4dc88c 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -436,6 +436,48 @@ static bool arm_v7m_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
 }
 #endif
 
+void arm_cpu_update_virq(ARMCPU *cpu)
+{
+    /*
+     * Update the interrupt level for VIRQ, which is the logical OR of
+     * the HCR_EL2.VI bit and the input line level from the GIC.
+     */
+    CPUARMState *env = &cpu->env;
+    CPUState *cs = CPU(cpu);
+
+    bool new_state = (env->cp15.hcr_el2 & HCR_VI) ||
+        (env->irq_line_state & CPU_INTERRUPT_VIRQ);
+
+    if (new_state != ((cs->interrupt_request & CPU_INTERRUPT_VIRQ) != 0)) {
+        if (new_state) {
+            cpu_interrupt(cs, CPU_INTERRUPT_VIRQ);
+        } else {
+            cpu_reset_interrupt(cs, CPU_INTERRUPT_VIRQ);
+        }
+    }
+}
+
+void arm_cpu_update_vfiq(ARMCPU *cpu)
+{
+    /*
+     * Update the interrupt level for VFIQ, which is the logical OR of
+     * the HCR_EL2.VF bit and the input line level from the GIC.
+     */
+    CPUARMState *env = &cpu->env;
+    CPUState *cs = CPU(cpu);
+
+    bool new_state = (env->cp15.hcr_el2 & HCR_VF) ||
+        (env->irq_line_state & CPU_INTERRUPT_VFIQ);
+
+    if (new_state != ((cs->interrupt_request & CPU_INTERRUPT_VFIQ) != 0)) {
+        if (new_state) {
+            cpu_interrupt(cs, CPU_INTERRUPT_VFIQ);
+        } else {
+            cpu_reset_interrupt(cs, CPU_INTERRUPT_VFIQ);
+        }
+    }
+}
+
 #ifndef CONFIG_USER_ONLY
 static void arm_cpu_set_irq(void *opaque, int irq, int level)
 {
@@ -457,9 +499,13 @@ static void arm_cpu_set_irq(void *opaque, int irq, int level)
 
     switch (irq) {
     case ARM_CPU_VIRQ:
+        assert(arm_feature(env, ARM_FEATURE_EL2));
+        arm_cpu_update_virq(cpu);
+        break;
     case ARM_CPU_VFIQ:
         assert(arm_feature(env, ARM_FEATURE_EL2));
-        /* fall through */
+        arm_cpu_update_vfiq(cpu);
+        break;
     case ARM_CPU_IRQ:
     case ARM_CPU_FIQ:
         if (level) {
diff --git a/target/arm/helper.c b/target/arm/helper.c
index f3878f505b7..771e4c3d0fb 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -3958,6 +3958,21 @@ static void hcr_write(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t value)
         tlb_flush(CPU(cpu));
     }
     env->cp15.hcr_el2 = value;
+
+    /*
+     * Updates to VI and VF require us to update the status of
+     * virtual interrupts, which are the logical OR of these bits
+     * and the state of the input lines from the GIC. (This requires
+     * that we have the iothread lock, which is done by marking the
+     * reginfo structs as ARM_CP_IO.)
+     * Note that if a write to HCR pends a VIRQ or VFIQ it is never
+     * possible for it to be taken immediately, because VIRQ and
+     * VFIQ are masked unless running at EL0 or EL1, and HCR
+     * can only be written at EL2.
+     */
+    g_assert(qemu_mutex_iothread_locked());
+    arm_cpu_update_virq(cpu);
+    arm_cpu_update_vfiq(cpu);
 }
 
 static void hcr_writehigh(CPUARMState *env, const ARMCPRegInfo *ri,
@@ -3978,11 +3993,12 @@ static void hcr_writelow(CPUARMState *env, const ARMCPRegInfo *ri,
 
 static const ARMCPRegInfo el2_cp_reginfo[] = {
     { .name = "HCR_EL2", .state = ARM_CP_STATE_AA64,
+      .type = ARM_CP_IO,
       .opc0 = 3, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 0,
       .access = PL2_RW, .fieldoffset = offsetof(CPUARMState, cp15.hcr_el2),
       .writefn = hcr_write },
     { .name = "HCR", .state = ARM_CP_STATE_AA32,
-      .type = ARM_CP_ALIAS,
+      .type = ARM_CP_ALIAS | ARM_CP_IO,
       .cp = 15, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 0,
       .access = PL2_RW, .fieldoffset = offsetof(CPUARMState, cp15.hcr_el2),
       .writefn = hcr_writelow },
@@ -4222,7 +4238,7 @@ static const ARMCPRegInfo el2_cp_reginfo[] = {
 
 static const ARMCPRegInfo el2_v8_cp_reginfo[] = {
     { .name = "HCR2", .state = ARM_CP_STATE_AA32,
-      .type = ARM_CP_ALIAS,
+      .type = ARM_CP_ALIAS | ARM_CP_IO,
       .cp = 15, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 4,
       .access = PL2_RW,
       .fieldoffset = offsetofhigh32(CPUARMState, cp15.hcr_el2),
-- 
2.19.1