3 files changed, 75 insertions, 5 deletions
diff --git a/target/arm/helper.c b/target/arm/helper.c
index ff1970981e..2746d3fdac 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -2646,11 +2646,28 @@ static void gt_recalc_timer(ARMCPU *cpu, int timeridx)
         gt->ctl = deposit32(gt->ctl, 2, 1, istatus);
 
         if (istatus) {
-            /* Next transition is when count rolls back over to zero */
-            nexttick = UINT64_MAX;
+            /*
+             * Next transition is when (count - offset) rolls back over to 0.
+             * If offset > count then this is when count == offset;
+             * if offset <= count then this is when count == offset + 2^64
+             * For the latter case we set nexttick to an "as far in future
+             * as possible" value and let the code below handle it.
+             */
+            if (offset > count) {
+                nexttick = offset;
+            } else {
+                nexttick = UINT64_MAX;
+            }
         } else {
-            /* Next transition is when we hit cval */
-            nexttick = gt->cval + offset;
+            /*
+             * Next transition is when (count - offset) == cval, i.e.
+             * when count == (cval + offset).
+             * If that would overflow, then again we set up the next interrupt
+             * for "as far in the future as possible" for the code below.
+             */
+            if (uadd64_overflow(gt->cval, offset, &nexttick)) {
+                nexttick = UINT64_MAX;
+            }
         }
         /*
          * Note that the desired next expiry time might be beyond the
diff --git a/tests/tcg/aarch64/Makefile.softmmu-target b/tests/tcg/aarch64/Makefile.softmmu-target
index 77c5018e02..4b03ef602e 100644
--- a/tests/tcg/aarch64/Makefile.softmmu-target
+++ b/tests/tcg/aarch64/Makefile.softmmu-target
@@ -45,7 +45,8 @@ TESTS+=memory-sve
 
 # Running
 QEMU_BASE_MACHINE=-M virt -cpu max -display none
-QEMU_OPTS+=$(QEMU_BASE_MACHINE) -semihosting-config enable=on,target=native,chardev=output -kernel
+QEMU_BASE_ARGS=-semihosting-config enable=on,target=native,chardev=output
+QEMU_OPTS+=$(QEMU_BASE_MACHINE) $(QEMU_BASE_ARGS) -kernel
 
 # console test is manual only
 QEMU_SEMIHOST=-serial none -chardev stdio,mux=on,id=stdio0 -semihosting-config enable=on,chardev=stdio0 -mon chardev=stdio0,mode=readline
@@ -56,6 +57,10 @@ run-semiconsole: semiconsole
 run-plugin-semiconsole-with-%: semiconsole
 	$(call skip-test, $<, "MANUAL ONLY")
 
+# vtimer test needs EL2
+QEMU_EL2_MACHINE=-machine virt,virtualization=on,gic-version=2 -cpu cortex-a57 -smp 4
+run-vtimer: QEMU_OPTS=$(QEMU_EL2_MACHINE) $(QEMU_BASE_ARGS) -kernel
+
 # Simple Record/Replay Test
 .PHONY: memory-record
 run-memory-record: memory-record memory
diff --git a/tests/tcg/aarch64/system/vtimer.c b/tests/tcg/aarch64/system/vtimer.c
new file mode 100644
index 0000000000..42f2f7796c
--- /dev/null
+++ b/tests/tcg/aarch64/system/vtimer.c
@@ -0,0 +1,48 @@
+/*
+ * Simple Virtual Timer Test
+ *
+ * Copyright (c) 2020 Linaro Ltd
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include <inttypes.h>
+#include <minilib.h>
+
+/* grabbed from Linux */
+#define __stringify_1(x...) #x
+#define __stringify(x...)   __stringify_1(x)
+
+#define read_sysreg(r) ({                                           \
+            uint64_t __val;                                         \
+            asm volatile("mrs %0, " __stringify(r) : "=r" (__val)); \
+            __val;                                                  \
+})
+
+#define write_sysreg(r, v) do {                     \
+        uint64_t __val = (uint64_t)(v);             \
+        asm volatile("msr " __stringify(r) ", %x0"  \
+                 : : "rZ" (__val));                 \
+} while (0)
+
+int main(void)
+{
+    int i;
+
+    ml_printf("VTimer Test\n");
+
+    write_sysreg(cntvoff_el2, 1);
+    write_sysreg(cntv_cval_el0, -1);
+    write_sysreg(cntv_ctl_el0, 1);
+
+    ml_printf("cntvoff_el2=%lx\n", read_sysreg(cntvoff_el2));
+    ml_printf("cntv_cval_el0=%lx\n", read_sysreg(cntv_cval_el0));
+    ml_printf("cntv_ctl_el0=%lx\n", read_sysreg(cntv_ctl_el0));
+
+    /* Now read cval a few times */
+    for (i = 0; i < 10; i++) {
+        ml_printf("%d: cntv_cval_el0=%lx\n", i, read_sysreg(cntv_cval_el0));
+    }
+
+    return 0;
+}