This commit adds a new system-mode TCG test to verify the behavior of
WFI, WFE, WFIT, and WFET instructions on AArch64.

The test ensures:
- WFI correctly wakes on a timer interrupt.
- WFE returns immediately if the event register is set (via SEV).
- WFIT and WFET correctly sleep until the specified timeout.

🤖 Generated with [eca](https://eca.dev)

Co-Authored-By: eca <noreply@eca.dev>

---
ajb:
  - removed an excess setting of QEMU_OPTS in the Makefile
---
 tests/tcg/aarch64/system/wfx.c            | 113 ++++++++++++++++++++++
 tests/tcg/aarch64/Makefile.softmmu-target |   2 +
 2 files changed, 115 insertions(+)
 create mode 100644 tests/tcg/aarch64/system/wfx.c

diff --git a/tests/tcg/aarch64/system/wfx.c b/tests/tcg/aarch64/system/wfx.c
new file mode 100644
index 00000000000..59436c381fd
--- /dev/null
+++ b/tests/tcg/aarch64/system/wfx.c
@@ -0,0 +1,113 @@
+/*
+ * WFX Instructions Test (WFI, WFE, WFIT, WFET)
+ *
+ * Copyright (c) 2024 Linaro Ltd
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include <stdint.h>
+#include <minilib.h>
+
+#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)
+
+#define isb() asm volatile("isb" : : : "memory")
+#define sev() asm volatile("sev" : : : "memory")
+#define wfi() asm volatile("wfi" : : : "memory")
+#define wfe() asm volatile("wfe" : : : "memory")
+#define wfit(reg) asm volatile("wfit %0" : : "r" (reg) : "memory")
+#define wfet(reg) asm volatile("wfet %0" : : "r" (reg) : "memory")
+
+static void wait_ticks(uint64_t ticks)
+{
+    uint64_t start = read_sysreg(cntvct_el0);
+    while ((read_sysreg(cntvct_el0) - start) < ticks) {
+        /* spin */
+    }
+}
+
+int main(void)
+{
+    uint64_t start, end, elapsed;
+    uint64_t timeout;
+
+    ml_printf("WFX Test\n");
+
+    /* 1. Test WFI with timer interrupt */
+    ml_printf("Testing WFI...");
+    /* Setup virtual timer to fire in 100000 ticks (~2ms at 50MHz) */
+    start = read_sysreg(cntvct_el0);
+    write_sysreg(cntv_tval_el0, 100000);
+    write_sysreg(cntv_ctl_el0, 1); /* Enable timer, no mask */
+    isb();
+
+    /*
+     * We don't have a full interrupt handler, but WFI should wake up
+     * when the interrupt is pending even if we have it masked at the CPU.
+     * PSTATE.I is set by boot code.
+     */
+    wfi();
+    end = read_sysreg(cntvct_el0);
+    elapsed = end - start;
+    if (elapsed < 100000) {
+        ml_printf("FAILED: WFI woke too early (%ld ticks)\n", elapsed);
+        return 1;
+    }
+    ml_printf("PASSED (elapsed %ld ticks)\n", elapsed);
+    write_sysreg(cntv_ctl_el0, 0); /* Disable timer */
+
+    /* 2. Test WFE and SEV */
+    ml_printf("Testing WFE/SEV...");
+    sev(); /* Set event register */
+    start = read_sysreg(cntvct_el0);
+    wfe(); /* Should return immediately */
+    end = read_sysreg(cntvct_el0);
+    elapsed = end - start;
+    if (elapsed > 1000) { /* Should be very fast */
+        ml_printf("FAILED: WFE slept despite SEV (%ld ticks)\n", elapsed);
+        return 1;
+    }
+    ml_printf("PASSED\n");
+
+    /* 3. Test WFIT */
+    ml_printf("Testing WFIT...");
+    start = read_sysreg(cntvct_el0);
+    timeout = start + 200000;
+    wfit(timeout);
+    end = read_sysreg(cntvct_el0);
+    elapsed = end - start;
+    if (elapsed < 200000) {
+        ml_printf("FAILED: WFIT woke too early (%ld ticks)\n", elapsed);
+        return 1;
+    }
+    ml_printf("PASSED (elapsed %ld ticks)\n", elapsed);
+
+    /* 4. Test WFET */
+    ml_printf("Testing WFET...");
+    start = read_sysreg(cntvct_el0);
+    timeout = start + 200000;
+    wfet(timeout);
+    end = read_sysreg(cntvct_el0);
+    elapsed = end - start;
+    if (elapsed < 200000) {
+        ml_printf("FAILED: WFET woke too early (%ld ticks)\n", elapsed);
+        return 1;
+    }
+    ml_printf("PASSED (elapsed %ld ticks)\n", elapsed);
+
+    ml_printf("ALL WFX TESTS PASSED\n");
+    return 0;
+}
diff --git a/tests/tcg/aarch64/Makefile.softmmu-target b/tests/tcg/aarch64/Makefile.softmmu-target
index f7a7d2b800f..84342c52cd7 100644
--- a/tests/tcg/aarch64/Makefile.softmmu-target
+++ b/tests/tcg/aarch64/Makefile.softmmu-target
@@ -102,6 +102,8 @@ run-pauth-3:
 	$(call skip-test, "RUN of pauth-3", "not built")
 endif
 
+wfx: CFLAGS += -march=armv8.7-a
+
 ifneq ($(CROSS_CC_HAS_ARMV8_MTE),)
 QEMU_MTE_ENABLED_MACHINE=-M virt,mte=on -cpu max -display none
 QEMU_OPTS_WITH_MTE_ON = $(QEMU_MTE_ENABLED_MACHINE) $(QEMU_BASE_ARGS) -kernel
-- 
2.47.3