On 16.03.21 18:26, Sean Christopherson wrote: > On Tue, Mar 16, 2021, Jan Kiszka wrote: >> On 16.03.21 17:50, Sean Christopherson wrote: >>> Rather than block all events in KVM, what about having QEMU "pause" the timer? >>> E.g. save MSR_TSC_DEADLINE and APIC_TMICT (or inspect the guest to find out >>> which flavor it's using), clear them to zero, then restore both when >>> single-stepping is disabled. I think that will work? >>> >> >> No one can stop the clock, and timers are only one source of interrupts. >> Plus they do not all come from QEMU, some also from KVM or in-kernel >> sources directly. > > But are any other sources of interrupts a chronic problem? I 100% agree that If you are debugging a problem, you are not interested in seening problems of the debugger, only real ones of your target. IOW: Yes, they are, even if less likely - for idle VMs. > this would not be a robust solution, but neither is blocking events in KVM. At > least with this approach, the blast radius is somewhat contained. > >> Would quickly become a mess. > > Maybe, but it'd be Qemu's mess ;-) > Nope, it would spread to KVM as well, as indicated above. Jan -- Siemens AG, T RDA IOT Corporate Competence Center Embedded Linux
