Andrea Arcangeli wrote: [snip] > So in short with the below fix applied, after a write_tsc(0,0), the > UP guest never return any error anymore. Previously it would return > frequent errors because sched_in wasn't properly invoked by svm.c and > it would crash at boot every single time after a write_tsc(0,0). > > The SMP guest of course still returns TSC errors but that's ok, the > smp host also return TSC errors, that's ok, it's only the UP guest > that is forbidden to have a not monotone TSC or the guest would crash > like it happened to me. > > I'm unsure if special_reload_db7 is needed at all, but it certainly > can't hurt so it's the only hack I left. >
It's needed, vmx (and IIRC svm) will clear out db7 so we must reload it. In fairness we need also reload it if the host had it set; it shouldn't be a hack but part of mainline. > Finally I can enjoy KVM stability too ;). If you always compiled your > host kernel with CONFIG_KVM=y on a recent kernels including the > preempt-notifiers, you could never run into this. If you compile your > host kernel with CONFIG_KVM=n please try to test this. > Unfortunately, this fails badly on Intel i386: > kvm: emulating preempt notifiers; do not benchmark on this machine > loaded kvm module (kvm-56-127-g433be51) > vmwrite error: reg c08 value d8 (err 3080) > [<f8baf9e2>] vmx_save_host_state+0x4f/0x162 [kvm_intel] > [<c0425803>] __cond_resched+0x25/0x3c > [<f91a22a4>] kvm_arch_vcpu_ioctl_run+0x16f/0x3a7 [kvm] > [<f919f244>] kvm_vcpu_ioctl+0xcb/0x28f [kvm] > [<c0421987>] enqueue_entity+0x2c0/0x2ea > [<c05a8340>] skb_dequeue+0x39/0x3f > [<c0604b6d>] unix_stream_recvmsg+0x3a2/0x4c3 > [<c0425c82>] scheduler_tick+0x1a1/0x274 > [<c0487329>] core_sys_select+0x21f/0x2fa > [<c043e9e6>] clockevents_program_event+0xb5/0xbc > [<c04c6853>] avc_has_perm+0x4e/0x58 > [<c04c7174>] inode_has_perm+0x66/0x6e > [<c0430bed>] recalc_sigpending+0xb/0x1d > [<c043231d>] dequeue_signal+0xa9/0x12a > [<c043cb95>] getnstimeofday+0x30/0xbf > [<c04c7205>] file_has_perm+0x89/0x91 > [<f919f179>] kvm_vcpu_ioctl+0x0/0x28f [kvm] > [<c04861b9>] do_ioctl+0x21/0xa0 > [<c048646f>] vfs_ioctl+0x237/0x249 > [<c04864cd>] sys_ioctl+0x4c/0x67 > [<c0404f26>] sysenter_past_esp+0x5f/0x85 > ======================= vmwrite error means the vmcs pointer was not loaded, probably because the sched_in event did not fire after a vcpu migration. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
