[PATCH v2 0/4] linux-user: Emulate /proc/cpuinfo on s390x

[PATCH v2 0/4] linux-user: Emulate /proc/cpuinfo on s390x

[Ilya Leoshkevich]

v1: https://lists.gnu.org/archive/html/qemu-devel/2023-06/msg00299.html
v1 -> v2: Add output examples (David).
          Simplify the CPU 0 special case (David).
          Fix building on s390x hosts.

Hi,

This series introduces /proc/cpuinfo linux-user emulation for s390x.
/proc/cpuinfo emulation already exists for sparc, hppa and riscv; this
series follows the pattern established for these platforms.

Patch 1 is a fix for an issue that I noticed while looking for ways to
get to the "identification" field.

Patches 2 and 3 introduce the necessary helpers.

Patch 4 is the actual implementation.

The trigger for this work is a bug report filed by Tulio [1], which has
to do with the llvm-project testcases failing under qemu-user.

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

Best regards,
Ilya

Ilya Leoshkevich (4):
  s390x/tcg: Fix CPU address returned by STIDP
  linux-user/elfload: Expose get_elf_hwcap() on s390x
  linux-user/elfload: Introduce elf_hwcap_str() on s390x
  linux-user: Emulate /proc/cpuinfo on s390x

 linux-user/elfload.c      |  29 ++++++++++-
 linux-user/loader.h       |   5 ++
 linux-user/syscall.c      | 106 +++++++++++++++++++++++++++++++++++++-
 target/s390x/cpu_models.c |   4 +-
 target/s390x/cpu_models.h |  10 +++-
 5 files changed, 148 insertions(+), 6 deletions(-)

-- 
2.40.1

[PATCH v2 1/4] s390x/tcg: Fix CPU address returned by STIDP

[Ilya Leoshkevich]

In qemu-user-s390x, /proc/cpuinfo contains:

	processor 0: version = 00,  identification = 000000,  machine = 8561
	processor 1: version = 00,  identification = 400000,  machine = 8561

The highest nibble is supposed to contain the CPU address, but it's off
by 2 bits. Fix the shift value and provide a symbolic constant for it.

With the fix we get:

	processor 0: version = 00,  identification = 000000,  machine = 8561
	processor 1: version = 00,  identification = 100000,  machine = 8561

Fixes: 076d4d39b65f ("s390x/cpumodel: wire up cpu type + id for TCG")
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 target/s390x/cpu_models.c |  4 ++--
 target/s390x/cpu_models.h | 10 +++++++++-
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/target/s390x/cpu_models.c b/target/s390x/cpu_models.c
index 457b5cb10c4..ae8880e81dc 100644
--- a/target/s390x/cpu_models.c
+++ b/target/s390x/cpu_models.c
@@ -607,8 +607,8 @@ void s390_realize_cpu_model(CPUState *cs, Error **errp)
 #if !defined(CONFIG_USER_ONLY)
     cpu->env.cpuid = s390_cpuid_from_cpu_model(cpu->model);
     if (tcg_enabled()) {
-        /* basic mode, write the cpu address into the first 4 bit of the ID */
-        cpu->env.cpuid = deposit64(cpu->env.cpuid, 54, 4, cpu->env.core_id);
+        cpu->env.cpuid = deposit64(cpu->env.cpuid, CPU_PHYS_ADDR_SHIFT,
+                                   CPU_PHYS_ADDR_BITS, cpu->env.core_id);
     }
 #endif
 }
diff --git a/target/s390x/cpu_models.h b/target/s390x/cpu_models.h
index fb1adc8b210..cc7305ec213 100644
--- a/target/s390x/cpu_models.h
+++ b/target/s390x/cpu_models.h
@@ -96,10 +96,18 @@ static inline bool s390_known_cpu_type(uint16_t type)
 {
     return s390_get_gen_for_cpu_type(type) != 0;
 }
+#define CPU_ID_SHIFT 32
+#define CPU_ID_BITS 24
+/*
+ * When cpu_id_format is 0 (basic mode), the leftmost 4 bits of cpu_id contain
+ * the rightmost 4 bits of the physical CPU address.
+ */
+#define CPU_PHYS_ADDR_BITS 4
+#define CPU_PHYS_ADDR_SHIFT (CPU_ID_SHIFT + CPU_ID_BITS - CPU_PHYS_ADDR_BITS)
 static inline uint64_t s390_cpuid_from_cpu_model(const S390CPUModel *model)
 {
     return ((uint64_t)model->cpu_ver << 56) |
-           ((uint64_t)model->cpu_id << 32) |
+           ((uint64_t)model->cpu_id << CPU_ID_SHIFT) |
            ((uint64_t)model->def->type << 16) |
            (model->def->gen == 7 ? 0 : (uint64_t)model->cpu_id_format << 15);
 }
-- 
2.40.1

[PATCH v2 2/4] linux-user/elfload: Expose get_elf_hwcap() on s390x

[Ilya Leoshkevich]

It is required for implementing /proc/cpuinfo emulation.

Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 linux-user/elfload.c | 2 +-
 linux-user/loader.h  | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 418ad92598c..49ec9ccc944 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1583,7 +1583,7 @@ static inline void init_thread(struct target_pt_regs *regs,
 #define GET_FEATURE(_feat, _hwcap) \
     do { if (s390_has_feat(_feat)) { hwcap |= _hwcap; } } while (0)
 
-static uint32_t get_elf_hwcap(void)
+uint32_t get_elf_hwcap(void)
 {
     /*
      * Let's assume we always have esan3 and zarch.
diff --git a/linux-user/loader.h b/linux-user/loader.h
index f375ee0679b..ad6ca9dbe35 100644
--- a/linux-user/loader.h
+++ b/linux-user/loader.h
@@ -56,4 +56,8 @@ abi_long memcpy_to_target(abi_ulong dest, const void *src,
 
 extern unsigned long guest_stack_size;
 
+#ifdef TARGET_S390X
+uint32_t get_elf_hwcap(void);
+#endif
+
 #endif /* LINUX_USER_LOADER_H */
-- 
2.40.1

[PATCH v2 3/4] linux-user/elfload: Introduce elf_hwcap_str() on s390x

[Ilya Leoshkevich]

It is required for implementing /proc/cpuinfo emulation.

Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 linux-user/elfload.c | 27 +++++++++++++++++++++++++++
 linux-user/loader.h  |  1 +
 2 files changed, 28 insertions(+)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 49ec9ccc944..d80d68484b6 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1605,6 +1605,33 @@ uint32_t get_elf_hwcap(void)
     return hwcap;
 }
 
+const char *elf_hwcap_str(uint32_t bit)
+{
+    static const char *hwcap_str[] = {
+        [HWCAP_S390_ESAN3]     = "esan3",
+        [HWCAP_S390_ZARCH]     = "zarch",
+        [HWCAP_S390_STFLE]     = "stfle",
+        [HWCAP_S390_MSA]       = "msa",
+        [HWCAP_S390_LDISP]     = "ldisp",
+        [HWCAP_S390_EIMM]      = "eimm",
+        [HWCAP_S390_DFP]       = "dfp",
+        [HWCAP_S390_HPAGE]     = "edat",
+        [HWCAP_S390_ETF3EH]    = "etf3eh",
+        [HWCAP_S390_HIGH_GPRS] = "highgprs",
+        [HWCAP_S390_TE]        = "te",
+        [HWCAP_S390_VXRS]      = "vx",
+        [HWCAP_S390_VXRS_BCD]  = "vxd",
+        [HWCAP_S390_VXRS_EXT]  = "vxe",
+        [HWCAP_S390_GS]        = "gs",
+        [HWCAP_S390_VXRS_EXT2] = "vxe2",
+        [HWCAP_S390_VXRS_PDE]  = "vxp",
+        [HWCAP_S390_SORT]      = "sort",
+        [HWCAP_S390_DFLT]      = "dflt",
+    };
+
+    return bit < ARRAY_SIZE(hwcap_str) ? hwcap_str[bit] : NULL;
+}
+
 static inline void init_thread(struct target_pt_regs *regs, struct image_info *infop)
 {
     regs->psw.addr = infop->entry;
diff --git a/linux-user/loader.h b/linux-user/loader.h
index ad6ca9dbe35..59cbeacf24f 100644
--- a/linux-user/loader.h
+++ b/linux-user/loader.h
@@ -58,6 +58,7 @@ extern unsigned long guest_stack_size;
 
 #ifdef TARGET_S390X
 uint32_t get_elf_hwcap(void);
+const char *elf_hwcap_str(uint32_t bit);
 #endif
 
 #endif /* LINUX_USER_LOADER_H */
-- 
2.40.1

[PATCH v2 4/4] linux-user: Emulate /proc/cpuinfo on s390x

[Ilya Leoshkevich]

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.

Output example:

	vendor_id       : IBM/S390
	# processors    : 12
	bogomips per cpu: 13370.00
	max thread id   : 0
	features	: esan3 zarch stfle msa
	facilities      : 0 1 2 3 4 7 9 16 17 18 19 21 22 24 25 27 30 31 32 33 34 35 37 40 41 45 49 51 52 53 57 58 61 69 71 72 75 76 77 129 130 131 135 138 146 148
	processor 0: version = 00,  identification = 000000,  machine = 8561
	processor 1: version = 00,  identification = 100000,  machine = 8561
	[...]

	cpu number      : 0
	version         : 00
	identification  : 000000
	machine         : 8561

	cpu number      : 1
	version         : 00
	identification  : 100000
	machine         : 8561
	[...]

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

Reported-by: Tulio Magno Quites Machado Filho <tuliom@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 linux-user/syscall.c | 106 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 104 insertions(+), 2 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 3e6ed51ce62..2d3070cfd62 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8232,7 +8232,7 @@ void target_exception_dump(CPUArchState *env, const char *fmt, int code)
 
 #if HOST_BIG_ENDIAN != TARGET_BIG_ENDIAN || \
     defined(TARGET_SPARC) || defined(TARGET_M68K) || defined(TARGET_HPPA) || \
-    defined(TARGET_RISCV)
+    defined(TARGET_RISCV) || defined(TARGET_S390X)
 static int is_proc(const char *filename, const char *entry)
 {
     return strcmp(filename, entry) == 0;
@@ -8339,6 +8339,107 @@ 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)
+{
+    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;
+
+    show_cpu_summary(cpu_env, fd);
+    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 +8465,8 @@ 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