Bug 498494

Linux / GCC generates the same opcode. So this is more likely to be related to something like 
Bool VG_(machine_get_hwcaps)( void )

This was on a VirtualBox instance. I hadn't realized just how bad the VB virtualization is on a modern amd64 PC.

CPU flags in VB
Flags:                   fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 cflsh mmx fxsr sse sse2 htt sse3 pclmulqdq ssse3 cx16 sse4_1 sse4_2 popcnt aes rdrnd syscall nx mmxext fxsr_opt rdtscp lm lahf_lm cmp_legacy cr8_legacy lzcnt sse4a misalignsse 3dnowprefetch

And natively
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl xtopology tsc_reliable nonstop_tsc cpuid extd_apicid aperfmperf rapl pni pclmuldq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm cmp_legacy cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw wdt topoext perfctr_core mwaitx cpb hw_pstate ssbd ibpb ibrs stibp fsgsbase bmi1 avx2 smep bmi2 erms invpcid cqm rdt_a avx512f avx512dq rdseed adx smap avx512ifma clflushopt clwb avx512cd sha_ni avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves user_shstk avx_vnni avx512_bf16 clzero xsaveerptr rdpru wbnoinvd cppc overflow_recov succor smca sme

That's less than half.

In gdb I see that CPUID is not setting either rdrand or rdseed. If I set them in gdb then at least rdseed runs OK.

Closing this as it looks like a VB limitation.