On 15/06/2016 16:25, Borislav Petkov wrote: > As to the error message, dear LKP friends, it happens because -cpu kvm64 > on native Intel hands in CPUID bits of the host, i.e., if you do this in > the guest: > > $ grep epb /proc/cpuinfo > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca > cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx lm constant_tsc nopl > eagerfpu pni cx16 x2apic hypervisor epb > > you should have "epb" there too which is among those bits.
Hmm, no, it doesn't work like that. EPB is bit 3 of CPUID[6].ECX. Under KVM you should only ever see bit 2 of EAX set in that leaf (ARAT). > I can reproduce the same issue on an AMD host too by booting my guest > with > > "-cpu kvm64,vendor=GenuineIntel" I cannot reproduce it with 4.6.0-rc3 in the (Fedora 22 AMD) host and 4.7.0-rc2 in the (Fedora 21) guest. QEMU is 2.4.1. > Paolo, Eduardo, question: can we hide certain CPUID bits from the guest > when booting with -cpu kvm64? > > In general, is there a way I can set or clear arbitrary CPUID bits so > that the guest sees what I want it to see? > > And I don't mean the predefined CPUID flags which you toggle with "+" or > "-" followed by flag name. Because -cpu kvm64,-epb doesn't work. It doesn't work because QEMU has no idea of what EPB even is. That bit really shouldn't be set. Can you bounce me the original report? Paolo
