2017-07-26 16:25+0200, Paolo Bonzini: > On 26/07/2017 16:07, Andi Kleen wrote: > > On Wed, Jul 26, 2017 at 11:26:07AM +0200, Paolo Bonzini wrote: > >> On 26/07/2017 02:20, Andi Kleen wrote: > >>> From: Andi Kleen <ak@xxxxxxxxxxxxxxx> > >>> > >>> KVM and perf have a special backdoor mechanism to report the IP for interrupts > >>> re-executed after vm exit. This works for the NMIs that perf normally uses. > >>> > >>> However when perf is in timer mode it doesn't work because the timer interrupt > >>> doesn't get this special treatment. This is common when KVM is running > >>> nested in another hypervisor which may not implement the PMU, so only > >>> timer mode is available. > >>> > >>> Call the functions to set up the backdoor IP also for non NMI interrupts. > >>> > >>> I renamed the functions to set up the backdoor IP reporting to be more > >>> appropiate for their new use. The SVM change is only compile tested. > >>> > >>> v2: Moved the functions inline. > >>> For the normal interrupt case the before/after functions are now > >>> called from x86.c, not arch specific code. > >> > >> You haven't removed the code from vmx_handle_external_intr and > >> svm_handle_external_intr. > > > > Ok. > > > >> > >>> For the NMI case we still need to call it in the architecture > >>> specific code, because it's already needed in the low level *_run > >>> functions. > >> > >> I must have been unclear; what I was asking is, can the calls cover > >> a much wider range of vcpu_enter_guest? > > > > Handling the external interrupt case from x86 without exporting > > is no problem (like my patch did) > > > > But to handle the NMI case it needs to be exported because > > the NMI case is directly handled in the lowlevel vcpu_runs*. > > > > And I'm not sure it's safe to set over the actual low level > > guest runs. e.g. the AMD code already seems to change interrupts > > there. > > AMD only enables interrupts while GIF is 0, so it would be safe. (The > processor switches GIF atomically to 1 with VMRUN and to 0 with #VMEXIT, > so "clgi;sti" means "enable interrupts while the guest runs" and is > paired with "cli;stgi" after VMRUN returns). > > The main difference would be for an NMI happening before the > VMRUN/VMRESUME instruction; it would be accounted to the guest rather > than the host. > > I guess it would be better done as a separate change anyway. I'll > commit your v2 with fixed vmx.c and svm.c. I just removed the extra code from arch handle_external_intr and queued, thanks.
