On Fri, Jan 13, 2017 at 04:51:45PM +0530, Aravinda Prasad wrote: > Enhance KVM to cause a guest exit with KVM_EXIT_NMI > exit reason upon a machine check exception (MCE) in > the guest address space if the KVM_CAP_PPC_FWNMI > capability is enabled (instead of delivering a 0x200 > interrupt to guest). This enables QEMU to build error > log and deliver machine check exception to guest via > guest registered machine check handler. > > This approach simplifies the delivery of machine > check exception to guest OS compared to the earlier > approach of KVM directly invoking 0x200 guest interrupt > vector. > > This design/approach is based on the feedback for the > QEMU patches to handle machine check exception. Details > of earlier approach of handling machine check exception > in QEMU and related discussions can be found at: > > https://lists.nongnu.org/archive/html/qemu-devel/2014-11/msg00813.html > > Note: > > This patch introduces a hook which is invoked at the time > of guest exit to facilitate the host-side handling of > machine check exception before the exception is passed > on to the guest. Hence, the host-side handling which was > performed earlier via machine_check_fwnmi is removed. > > The reasons for this approach is (i) it is not possible > to distinguish whether the exception occurred in the > guest or the host from the pt_regs passed on the > machine_check_exception(). Hence machine_check_exception() > calls panic, instead of passing on the exception to > the guest, if the machine check exception is not > recoverable. (ii) the approach introduced in this > patch gives opportunity to the host kernel to perform > actions in virtual mode before passing on the exception > to the guest. This approach does not require complex > tweaks to machine_check_fwnmi and friends. > > Signed-off-by: Aravinda Prasad <aravinda@xxxxxxxxxxxxxxxxxx> > Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> This patch mostly looks OK. I have a few relatively minor comments below. > --- > arch/powerpc/kvm/book3s_hv.c | 27 +++++++++++++----- > arch/powerpc/kvm/book3s_hv_rmhandlers.S | 47 ++++++++++++++++--------------- > arch/powerpc/platforms/powernv/opal.c | 10 +++++++ > 3 files changed, 54 insertions(+), 30 deletions(-) > > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c > index 3686471..cae4921 100644 > --- a/arch/powerpc/kvm/book3s_hv.c > +++ b/arch/powerpc/kvm/book3s_hv.c > @@ -123,6 +123,7 @@ MODULE_PARM_DESC(halt_poll_ns_shrink, "Factor halt poll time is shrunk by"); > > static void kvmppc_end_cede(struct kvm_vcpu *vcpu); > static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu); > +static void kvmppc_machine_check_hook(void); > > static inline struct kvm_vcpu *next_runnable_thread(struct kvmppc_vcore *vc, > int *ip) > @@ -954,15 +955,14 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu, > r = RESUME_GUEST; > break; > case BOOK3S_INTERRUPT_MACHINE_CHECK: > + /* Exit to guest with KVM_EXIT_NMI as exit reason */ > + run->exit_reason = KVM_EXIT_NMI; > + r = RESUME_HOST; > /* > - * Deliver a machine check interrupt to the guest. > - * We have to do this, even if the host has handled the > - * machine check, because machine checks use SRR0/1 and > - * the interrupt might have trashed guest state in them. > + * Invoke host-kernel handler to perform any host-side > + * handling before exiting the guest. > */ > - kvmppc_book3s_queue_irqprio(vcpu, > - BOOK3S_INTERRUPT_MACHINE_CHECK); > - r = RESUME_GUEST; > + kvmppc_machine_check_hook(); Note that this won't necessarily be called on the same CPU that received the machine check. This will be called on thread 0 of the core (or subcore), whereas the machine check could have occurred on some other thread. Are you sure that the machine check handling code will be OK with that? > break; > case BOOK3S_INTERRUPT_PROGRAM: > { > @@ -3491,6 +3491,19 @@ static void kvmppc_irq_bypass_del_producer_hv(struct irq_bypass_consumer *cons, > } > #endif > > +/* > + * Hook to handle machine check exceptions occurred inside a guest. > + * This hook is invoked from host virtual mode from KVM before exiting > + * the guest with KVM_EXIT_NMI exit reason. This gives an opportunity > + * for the host to take action (if any) before passing on the machine > + * check exception to the guest kernel. > + */ > +static void kvmppc_machine_check_hook(void) > +{ > + if (ppc_md.machine_check_exception) > + ppc_md.machine_check_exception(NULL); > +} What is the advantage of having this as a separate function, as opposed to just putting those two lines of code in line in the one place where this gets called? Paul. -- 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
