On Thursday 18 October 2012, Avi Kivity wrote: > On 10/18/2012 11:35 AM, Gleb Natapov wrote: > > You misunderstood the description. V_INTR_MASKING=1 means that > > CR8 writes are not propagated to real HW APIC. > > > > But KVM does not trap access to CR8 unconditionally. It enables > > CR8 intercept only when there is pending interrupt in IRR that > > cannot be immediately delivered due to current TPR value. This > > should eliminate 99% of CR8 intercepts. > > Right. You will need to expose the alternate encoding of cr8 (IIRC > lock mov reg, cr0) on AMD via cpuid, but otherwise it should just > work. Be aware that this will break cross-vendor migration. I get an exception and I am not sure why: kvm_entry: vcpu 0 kvm_exit: reason write_cr8 rip 0xd0203788 info 0 0 kvm_emulate_insn: 0:d0203788: f0 0f 22 c0 (prot32) kvm_inj_exception: #UD (0x0) This is qemu-kvm 1.1.2 on Linux 3.2. When I look at arch/x86/kvm/emulate.c (both the current and the v3.2 version), I don't see any special case handling for "lock mov reg, cr0" to mean "mov reg, cr8". Before I spend lots of time on debugging my code, can you verify if the alternate encoding of cr8 is actually supported in kvm or if it is maybe missing? Thanks in advance. Cheers, Stefan -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
