"Gowans, James" <jgowans@xxxxxxxxxx> writes: > Hi Sean, > > Blast from the past but I've just been bitten by this patch when > rebasing across v6.4. > > On Fri, 2023-05-12 at 16:31 -0700, Sean Christopherson wrote: >> Use syscore_ops.shutdown to disable hardware virtualization during a >> reboot instead of using the dedicated reboot_notifier so that KVM disables >> virtualization _after_ system_state has been updated. This will allow >> fixing a race in KVM's handling of a forced reboot where KVM can end up >> enabling hardware virtualization between kernel_restart_prepare() and >> machine_restart(). > > The issue is that, AFAICT, the syscore_ops.shutdown are not called when > doing a kexec. Reboot notifiers are called across kexec via: > > kernel_kexec > kernel_restart_prepare > blocking_notifier_call_chain > kvm_reboot > > So after this patch, KVM is not shutdown during kexec; if hardware virt > mode is enabled then the kexec hangs in exactly the same manner as you > describe with the reboot. kernel_restart_prepare calls device_shutdown. Which should call all of the shutdown operations. This has been the way the code has been structured since December 2005. > Some specific shutdown callbacks, for example IOMMU, HPET, IRQ, etc are > called in native_machine_shutdown, but KVM is not one of these. > > Thoughts on possible ways to fix this: > a) go back to reboot notifiers > b) get kexec to call syscore_shutdown() to invoke all of these callbacks > c) Add a KVM-specific callback to native_machine_shutdown(); we only > need this for Intel x86, right? > > My slight preference is towards adding syscore_shutdown() to kexec, but > I'm not sure that's feasible. Adding kexec maintainers for input. Why isn't device_suthdown calling syscore_shutdown? What problem are you running into with your rebase that worked with reboot notifiers that is not working with syscore_shutdown? Eric
