On Tue, Aug 11, 2020 at 09:57:55AM +0200, Jürgen Groß wrote: > On 11.08.20 09:41, Peter Zijlstra wrote: > > On Fri, Aug 07, 2020 at 05:19:03PM +0200, Marco Elver wrote: > > > > > My hypothesis here is simply that kvm_wait() may be called in a place > > > where we get the same case I mentioned to Peter, > > > > > > raw_local_irq_save(); /* or other IRQs off without tracing */ > > > ... > > > kvm_wait() /* IRQ state tracing gets confused */ > > > ... > > > raw_local_irq_restore(); > > > > > > and therefore, using raw variants in kvm_wait() works. It's also safe > > > because it doesn't call any other libraries that would result in corrupt > > > > Yes, this is definitely an issue. > > > > Tracing, we also musn't call into tracing when using raw_local_irq_*(). > > Because then we re-intoduce this same issue all over again. > > > > Both halt() and safe_halt() are more paravirt calls, but given we're in > > a KVM paravirt call already, I suppose we can directly use native_*() > > here. > > > > Something like so then... I suppose, but then the Xen variants need TLC > > too. > > Just to be sure I understand you correct: > > You mean that xen_qlock_kick() and xen_qlock_wait() and all functions > called by those should gain the "notrace" attribute, right? > > I am not sure why the kick variants need it, though. IMO those are > called only after the lock has been released, so they should be fine > without notrace. The issue happens when someone uses arch_spinlock_t under raw_local_irq_*(). > And again: we shouldn't forget the Hyper-V variants. Bah, my grep failed :/ Also *groan*, that's calling apic->send_IPI(). _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
