On Wed, Dec 07, 2011 at 04:41:17PM +0200, Avi Kivity wrote: > On 12/05/2011 10:18 PM, Eric B Munson wrote: > > Changes from V4: > > Rename KVM_GUEST_PAUSED to KVMCLOCK_GUEST_PAUSED > > Add description of KVMCLOCK_GUEST_PAUSED ioctl to api.txt > > > > Changes from V3: > > Include CC's on patch 3 > > Drop clear flag ioctl and have the watchdog clear the flag when it is reset > > > > Changes from V2: > > A new kvm functions defined in kvm_para.h, the only change to pvclock is the > > initial flag definition > > > > Changes from V1: > > (Thanks Marcelo) > > Host code has all been moved to arch/x86/kvm/x86.c > > KVM_PAUSE_GUEST was renamed to KVM_GUEST_PAUSED > > > > When a guest kernel is stopped by the host hypervisor it can look like a soft > > lockup to the guest kernel. This false warning can mask later soft lockup > > warnings which may be real. This patch series adds a method for a host > > hypervisor to communicate to a guest kernel that it is being stopped. The > > final patch in the series has the watchdog check this flag when it goes to > > issue a soft lockup warning and skip the warning if the guest knows it was > > stopped. > > > > It was attempted to solve this in Qemu, but the side effects of saving and > > restoring the clock and tsc for each vcpu put the wall clock of the guest behind > > by the amount of time of the pause. This forces a guest to have ntp running > > in order to keep the wall clock accurate. > > Having this controlled from userspace means it doesn't work for SIGSTOP > or for long scheduling delays. What about doing this automatically > based on preempt notifiers? Long scheduling delays should be considered hangups from the guest perspective. About SIGSTOP, that is a corner case. Unsure if its even properly supported by QEMU. -- 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
