[PATCH 4/4] linux-user: Emulate /proc/cpuinfo on s390x

[Ilya Leoshkevich <iii@linux.ibm.com>]

Some s390x userspace programs are confused when seeing a foreign
/proc/cpuinfo [1]. Add the emulation for s390x; follow the respective
kernel code structure where possible.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=2211472

Reported-by: Tulio Magno Quites Machado Filho <tuliom@redhat.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 linux-user/syscall.c | 106 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 105 insertions(+), 1 deletion(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 3e6ed51ce62..d142e09dc70 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8339,6 +8339,109 @@ static int open_cpuinfo(CPUArchState *cpu_env, int fd)
 }
 #endif
 
+#if defined(TARGET_S390X)
+/*
+ * Emulate what a Linux kernel running in qemu-system-s390x -M accel=tcg would
+ * show in /proc/cpuinfo.
+ *
+ * Skip the following in order to match the missing support in op_ecag():
+ * - show_cacheinfo().
+ * - show_cpu_topology().
+ * - show_cpu_mhz().
+ *
+ * Use fixed values for certain fields:
+ * - bogomips per cpu - from a qemu-system-s390x run.
+ * - max thread id = 0, since SMT / SIGP_SET_MULTI_THREADING is not supported.
+ *
+ * Keep the code structure close to arch/s390/kernel/processor.c.
+ */
+
+static void show_facilities(int fd)
+{
+    size_t sizeof_stfl_bytes = 2048;
+    g_autofree uint8_t *stfl_bytes = g_new0(uint8_t, sizeof_stfl_bytes);
+    unsigned int bit;
+
+    dprintf(fd, "facilities      :");
+    s390_get_feat_block(S390_FEAT_TYPE_STFL, stfl_bytes);
+    for (bit = 0; bit < sizeof_stfl_bytes * 8; bit++) {
+        if (test_be_bit(bit, stfl_bytes)) {
+            dprintf(fd, " %d", bit);
+        }
+    }
+    dprintf(fd, "\n");
+}
+
+static int cpu_ident(unsigned long n)
+{
+    return deposit32(0, CPU_ID_BITS - CPU_PHYS_ADDR_BITS, CPU_PHYS_ADDR_BITS,
+                     n);
+}
+
+static void show_cpu_summary(CPUArchState *cpu_env, int fd)
+{
+    S390CPUModel *model = env_archcpu(cpu_env)->model;
+    int num_cpus = sysconf(_SC_NPROCESSORS_ONLN);
+    uint32_t elf_hwcap = get_elf_hwcap();
+    const char *hwcap_str;
+    int i;
+
+    dprintf(fd, "vendor_id       : IBM/S390\n"
+                "# processors    : %i\n"
+                "bogomips per cpu: 13370.00\n",
+            num_cpus);
+    dprintf(fd, "max thread id   : 0\n");
+    dprintf(fd, "features\t: ");
+    for (i = 0; i < sizeof(elf_hwcap) * 8; i++) {
+        if (!(elf_hwcap & (1 << i))) {
+            continue;
+        }
+        hwcap_str = elf_hwcap_str(i);
+        if (hwcap_str) {
+            dprintf(fd, "%s ", hwcap_str);
+        }
+    }
+    dprintf(fd, "\n");
+    show_facilities(fd);
+    for (i = 0; i < num_cpus; i++) {
+        dprintf(fd, "processor %d: "
+               "version = %02X,  "
+               "identification = %06X,  "
+               "machine = %04X\n",
+               i, model->cpu_ver, cpu_ident(i), model->def->type);
+    }
+}
+
+static void show_cpu_ids(CPUArchState *cpu_env, int fd, unsigned long n)
+{
+    S390CPUModel *model = env_archcpu(cpu_env)->model;
+
+    dprintf(fd, "version         : %02X\n", model->cpu_ver);
+    dprintf(fd, "identification  : %06X\n", cpu_ident(n));
+    dprintf(fd, "machine         : %04X\n", model->def->type);
+}
+
+static void show_cpuinfo(CPUArchState *cpu_env, int fd, unsigned long n)
+{
+    if (n == 0) {
+        show_cpu_summary(cpu_env, fd);
+    }
+    dprintf(fd, "\ncpu number      : %ld\n", n);
+    show_cpu_ids(cpu_env, fd, n);
+}
+
+static int open_cpuinfo(CPUArchState *cpu_env, int fd)
+{
+    int num_cpus = sysconf(_SC_NPROCESSORS_ONLN);
+    int i;
+
+    for (i = 0; i < num_cpus; i++) {
+        show_cpuinfo(cpu_env, fd, i);
+    }
+    return 0;
+}
+#endif
+
 #if defined(TARGET_M68K)
 static int open_hardware(CPUArchState *cpu_env, int fd)
 {
@@ -8364,7 +8467,8 @@ int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *pathname,
 #if HOST_BIG_ENDIAN != TARGET_BIG_ENDIAN
         { "/proc/net/route", open_net_route, is_proc },
 #endif
-#if defined(TARGET_SPARC) || defined(TARGET_HPPA) || defined(TARGET_RISCV)
+#if defined(TARGET_SPARC) || defined(TARGET_HPPA) || \
+    defined(TARGET_RISCV) || defined(TARGET_S390X)
         { "/proc/cpuinfo", open_cpuinfo, is_proc },
 #endif
 #if defined(TARGET_M68K)
-- 
2.40.1