On 1/9/19 7:35 AM, Paul Menzel wrote: > Dear Thomas, > > > On 01/09/19 14:16, Thomas Gleixner wrote: > >> On Wed, 9 Jan 2019, Paul Menzel wrote: >>> I get the same with microcode updates applied. >>> >>> $ dmesg | grep 'microcode: CPU0: patch_level' >>> [ 3.809210] microcode: CPU0: patch_level=0x0600063e >>> $ sudo modprobe msr >>> $ sudo ./wrmsr 0x49 0x1 >>> wrmsr: CPU 0 cannot set MSR 0x00000049 to 0x0000000000000001 >>> >>>> Could you please post /proc/cpuinfo from such a boot as well? >> >> /proc/cpuinfo unfortunately does not contain the amd specific IBPB flag, >> but the dmesg of the original report says: >> >> Spectre V2 : mitigation: Enabling conditional Indirect Branch Prediction >> Barrier >> >> which means, that the CPUID bit is set. >> >> Can you please provide the output of: >> >> cpuid -1 -l 0x80000008 -r >> >> On my AMD Opteron(TM) Processor 6276 with microcode 0x600063d loaded I get: >> >> 0x80000008 0x00: eax=0x00003030 ebx=0x00000000 ecx=0x0000500f >> edx=0x00000000 >> >> EBX is 0, which means that X86_FEATURE_AMD_IBPB is not enabled. So the >> kernel does not try to use the speculation control MSR (0x49). > > With CPUID 20180519, I get the output below with both microcode update > versions. > > 0x600063d: > > $ sudo ./cpuid -1 -l 0x80000008 -r > CPU: > 0x80000008 0x00: eax=0x00003030 ebx=0x00000000 ecx=0x0000500f > edx=0x00000000 > > 0x600063e: > > $ sudo ./cpuid -1 -l 0x80000008 -r > CPU: > 0x80000008 0x00: eax=0x00003030 ebx=0x00000000 ecx=0x0000500f > edx=0x00000000 >
Hmmm... so ebx is 0 for both versions, so I'm not sure how IBPB is being set. What's the CPUID output for 0x07 (cpuid -1 -l 0x07 -r)? Thanks, Tom > > Kind regards, > > Paul >
