[Qemu-devel] [PATCH v3 4/6] tcg-s390: Use qemu_getauxval in query_facilities

[Richard Henderson <rth@twiddle.net>]

No need to set up a SIGILL signal handler for detection anymore.

Remove a ton of sanity checks that must be true, given that we're
requiring a 64-bit build (the note about 31-bit KVM is satisfied
by configuring with TCI).

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 include/elf.h         | 14 ++++++++
 tcg/s390/tcg-target.c | 95 +++++++--------------------------------------------
 2 files changed, 26 insertions(+), 83 deletions(-)

diff --git a/include/elf.h b/include/elf.h
index 654e33b..a6790c4 100644
--- a/include/elf.h
+++ b/include/elf.h
@@ -479,6 +479,20 @@ typedef struct {
 #define HWCAP_SPARC_V9		16
 #define HWCAP_SPARC_ULTRA3	32
 
+/* Bits present in AT_HWCAP for s390.  */
+
+#define HWCAP_S390_ESAN3        1
+#define HWCAP_S390_ZARCH        2
+#define HWCAP_S390_STFLE        4
+#define HWCAP_S390_MSA          8
+#define HWCAP_S390_LDISP        16
+#define HWCAP_S390_EIMM         32
+#define HWCAP_S390_DFP          64
+#define HWCAP_S390_HPAGE        128
+#define HWCAP_S390_ETF3EH       256
+#define HWCAP_S390_HIGH_GPRS    512
+#define HWCAP_S390_TE           1024
+
 /*
  * 68k ELF relocation types
  */
diff --git a/tcg/s390/tcg-target.c b/tcg/s390/tcg-target.c
index 0a4f3be..248726e 100644
--- a/tcg/s390/tcg-target.c
+++ b/tcg/s390/tcg-target.c
@@ -31,6 +31,8 @@
 #error "unsupported code generation mode"
 #endif
 
+#include "elf.h"
+
 /* ??? The translation blocks produced by TCG are generally small enough to
    be entirely reachable with a 16-bit displacement.  Leaving the option for
    a 32-bit displacement here Just In Case.  */
@@ -2233,91 +2235,18 @@ static void sigill_handler(int sig)
 
 static void query_facilities(void)
 {
-    struct sigaction sa_old, sa_new;
-    register int r0 __asm__("0");
-    register void *r1 __asm__("1");
-    int fail;
-
-    memset(&sa_new, 0, sizeof(sa_new));
-    sa_new.sa_handler = sigill_handler;
-    sigaction(SIGILL, &sa_new, &sa_old);
-
-    /* First, try STORE FACILITY LIST EXTENDED.  If this is present, then
-       we need not do any more probing.  Unfortunately, this itself is an
-       extension and the original STORE FACILITY LIST instruction is
-       kernel-only, storing its results at absolute address 200.  */
-    /* stfle 0(%r1) */
-    r1 = &facilities;
-    asm volatile(".word 0xb2b0,0x1000"
-                 : "=r"(r0) : "0"(0), "r"(r1) : "memory", "cc");
-
-    if (got_sigill) {
-        /* STORE FACILITY EXTENDED is not available.  Probe for one of each
-           kind of instruction that we're interested in.  */
-        /* ??? Possibly some of these are in practice never present unless
-           the store-facility-extended facility is also present.  But since
-           that isn't documented it's just better to probe for each.  */
-
-        /* Test for z/Architecture.  Required even in 31-bit mode.  */
-        got_sigill = 0;
-        /* agr %r0,%r0 */
-        asm volatile(".word 0xb908,0x0000" : "=r"(r0) : : "cc");
-        if (!got_sigill) {
-            facilities |= FACILITY_ZARCH_ACTIVE;
-        }
-
-        /* Test for long displacement.  */
-        got_sigill = 0;
-        /* ly %r0,0(%r1) */
-        r1 = &facilities;
-        asm volatile(".word 0xe300,0x1000,0x0058"
-                     : "=r"(r0) : "r"(r1) : "cc");
-        if (!got_sigill) {
-            facilities |= FACILITY_LONG_DISP;
-        }
-
-        /* Test for extended immediates.  */
-        got_sigill = 0;
-        /* afi %r0,0 */
-        asm volatile(".word 0xc209,0x0000,0x0000" : : : "cc");
-        if (!got_sigill) {
-            facilities |= FACILITY_EXT_IMM;
-        }
-
-        /* Test for general-instructions-extension.  */
-        got_sigill = 0;
-        /* msfi %r0,1 */
-        asm volatile(".word 0xc201,0x0000,0x0001");
-        if (!got_sigill) {
-            facilities |= FACILITY_GEN_INST_EXT;
-        }
-    }
-
-    sigaction(SIGILL, &sa_old, NULL);
+    unsigned long hwcap = qemu_getauxval(AT_HWCAP);
 
-    /* The translator currently uses these extensions unconditionally.
-       Pruning this back to the base ESA/390 architecture doesn't seem
-       worthwhile, since even the KVM target requires z/Arch.  */
-    fail = 0;
-    if ((facilities & FACILITY_ZARCH_ACTIVE) == 0) {
-        fprintf(stderr, "TCG: z/Arch facility is required.\n");
-        fprintf(stderr, "TCG: Boot with a 64-bit enabled kernel.\n");
-        fail = 1;
-    }
-    if ((facilities & FACILITY_LONG_DISP) == 0) {
-        fprintf(stderr, "TCG: long-displacement facility is required.\n");
-        fail = 1;
-    }
+    /* Is STORE FACILITY LIST EXTENDED available?  Honestly, I believe this
+       is present on all 64-bit systems, but let's check for it anyway.  */
+    if (hwcap & HWCAP_S390_STFLE) {
+        register int r0 __asm__("0");
+        register void *r1 __asm__("1");
 
-    /* So far there's just enough support for 31-bit mode to let the
-       compile succeed.  This is good enough to run QEMU with KVM.  */
-    if (sizeof(void *) != 8) {
-        fprintf(stderr, "TCG: 31-bit mode is not supported.\n");
-        fail = 1;
-    }
-
-    if (fail) {
-        exit(-1);
+        /* stfle 0(%r1) */
+        r1 = &facilities;
+        asm volatile(".word 0xb2b0,0x1000"
+                     : "=r"(r0) : "0"(0), "r"(r1) : "memory", "cc");
     }
 }
 
-- 
1.8.3.1