target/i386: implement RDPID in TCG

RDPID corresponds to a RDMSR(TSC_AUX); however, it is unprivileged
so for user-mode emulation we must provide the value that the kernel
places in the MSR.  For Linux, it is a combination of the current CPU
and the current NUMA node, both of which can be retrieved with getcpu(2).
Also try sched_getcpu(), which might be there on the BSDs.  If there is
no portable way to retrieve the current CPU id from userspace, return 0.

RDTSCP is reimplemented as RDTSC + RDPID ECX; the differences in terms
of serializability are not relevant to QEMU.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 15 insertions, 6 deletions

diff --git a/target/i386/tcg/misc_helper.c b/target/i386/tcg/misc_helper.c
index 5f7a3061ca..868f36ab7f 100644
--- a/target/i386/tcg/misc_helper.c
+++ b/target/i386/tcg/misc_helper.c
@@ -75,12 +75,6 @@ void helper_rdtsc(CPUX86State *env)
     env->regs[R_EDX] = (uint32_t)(val >> 32);
 }
 
-void helper_rdtscp(CPUX86State *env)
-{
-    helper_rdtsc(env);
-    env->regs[R_ECX] = (uint32_t)(env->tsc_aux);
-}
-
 G_NORETURN void helper_rdpmc(CPUX86State *env)
 {
     if (((env->cr[4] & CR4_PCE_MASK) == 0 ) &&
@@ -137,3 +131,18 @@ void helper_wrpkru(CPUX86State *env, uint32_t ecx, uint64_t val)
     env->pkru = val;
     tlb_flush(cs);
 }
+
+target_ulong HELPER(rdpid)(CPUX86State *env)
+{
+#if defined CONFIG_SOFTMMU
+    return env->tsc_aux;
+#elif defined CONFIG_LINUX && defined CONFIG_GETCPU
+    unsigned cpu, node;
+    getcpu(&cpu, &node);
+    return (node << 12) | (cpu & 0xfff);
+#elif defined CONFIG_SCHED_GETCPU
+    return sched_getcpu();
+#else
+    return 0;
+#endif
+}