It seems that real mode virtualisation on Nehalem has regressed in 4.2: On Sun, 2015-10-25 at 10:08 +0100, Stefan Fritsch wrote: [...] > I cannot use KVM with 4.2, qemu loops with 100% CPU during seabios > initialization. Booting with the latest linux-image-4.1.0-2-amd64 fixes > the issue. [...] > kvm tracing shows: > > ... > qemu-system-x86-3219 [007] .... 1090.728418: kvm_set_irq: gsi 12 level 0 source 0 > qemu-system-x86-3219 [007] .... 1090.728418: kvm_pic_set_irq: chip 1 pin 4 (edge|masked) > qemu-system-x86-3219 [007] .... 1090.728419: kvm_ioapic_set_irq: pin 12 dst 0 vec=0 (Fixed|physical|edge|masked) > qemu-system-x86-3219 [007] .... 1090.728419: kvm_set_irq: gsi 1 level 0 source 0 > qemu-system-x86-3219 [007] .... 1090.728420: kvm_pic_set_irq: chip 0 pin 1 (edge|masked) > qemu-system-x86-3219 [007] .... 1090.728420: kvm_ioapic_set_irq: pin 1 dst 0 vec=0 (Fixed|physical|edge|masked) > qemu-system-x86-3219 [007] .... 1090.728420: kvm_set_irq: gsi 12 level 0 source 0 > qemu-system-x86-3219 [007] .... 1090.728421: kvm_pic_set_irq: chip 1 pin 4 (edge|masked) > qemu-system-x86-3219 [007] .... 1090.728421: kvm_ioapic_set_irq: pin 12 dst 0 vec=0 (Fixed|physical|edge|masked) > qemu-system-x86-3219 [007] .... 1090.728723: kvm_set_irq: gsi 0 level 0 source 0 > qemu-system-x86-3219 [007] .... 1090.728724: kvm_pic_set_irq: chip 0 pin 0 (edge) > qemu-system-x86-3219 [007] .... 1090.728725: kvm_ioapic_set_irq: pin 2 dst 0 vec=0 (Fixed|physical|edge|masked) > qemu-system-x86-3219 [007] .... 1090.728725: kvm_set_irq: gsi 0 level 0 source 0 > qemu-system-x86-3219 [007] .... 1090.728725: kvm_pic_set_irq: chip 0 pin 0 (edge) > qemu-system-x86-3219 [007] .... 1090.728725: kvm_ioapic_set_irq: pin 2 dst 0 vec=0 (Fixed|physical|edge|masked) > qemu-system-x86-3219 [007] .... 1090.728726: kvm_set_irq: gsi 0 level 0 source 0 > qemu-system-x86-3219 [007] .... 1090.728726: kvm_pic_set_irq: chip 0 pin 0 (edge) > qemu-system-x86-3219 [007] .... 1090.728726: kvm_ioapic_set_irq: pin 2 dst 0 vec=0 (Fixed|physical|edge|masked) > qemu-system-x86-3221 [000] d... 1090.729926: kvm_write_tsc_offset: vcpu=0 prev=18446740943986499809 next=18446740943986499809 > qemu-system-x86-3221 [000] .... 1090.729927: kvm_track_tsc: vcpu_id 0 masterclock 1 offsetmatched 0 nr_online 1 hostclock tsc > qemu-system-x86-3221 [000] .... 1090.730004: kvm_update_master_clock: masterclock 1 hostclock tsc offsetmatched 1 > qemu-system-x86-3221 [000] d... 1090.730010: kvm_entry: vcpu 0 > qemu-system-x86-3221 [000] .... 1090.730013: kvm_emulate_insn: ffff0000:fff0:ea 5b e0 00 f0 (real) > qemu-system-x86-3221 [000] d... 1090.730016: kvm_entry: vcpu 0 > qemu-system-x86-3221 [000] d... 1090.730017: kvm_exit: reason EPT_VIOLATION rip 0xe05b info 81 0 > qemu-system-x86-3221 [000] .... 1090.730018: kvm_page_fault: address feffc000 error_code 81 > qemu-system-x86-3221 [000] d... 1090.730032: kvm_entry: vcpu 0 > qemu-system-x86-3221 [000] d... 1090.730034: kvm_exit: reason EXCEPTION_NMI rip 0xe05b info 0 80000b08 > qemu-system-x86-3221 [000] .... 1090.730035: kvm_inj_exception: #DF (0x0) > qemu-system-x86-3221 [000] d... 1090.730040: kvm_entry: vcpu 0 > qemu-system-x86-3221 [000] d... 1090.730041: kvm_exit: reason EXCEPTION_NMI rip 0xfea5 info 0 80000b08 > qemu-system-x86-3221 [000] .... 1090.730041: kvm_inj_exception: #DF (0x0) > qemu-system-x86-3221 [000] d... 1090.730043: kvm_entry: vcpu 0 > ... [...] > I am rather surprised that there is no bug report about this yet, so I > guess it only happens on some hardware. Mine is a Core i7-860. Ben. -- Ben Hutchings Beware of bugs in the above code; I have only proved it correct, not tried it. - Donald Knuth
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