Messages in this thread | | | Subject | Re: General protection fault in `switch_mm_irqs_off()` | From | Paul Menzel <> | Date | Wed, 9 Jan 2019 14:35:57 +0100 |
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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
Kind regards,
Paul
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