Re: [PATCH] QEMU-KVM: MCE: Relay UCR MCE to guest

[Huang Ying <ying.huang@intel.com>]

On Tue, 2009-09-08 at 14:44 +0800, Avi Kivity wrote: 
> On 09/07/2009 11:32 AM, Huang Ying wrote:
> > UCR (uncorrected recovery) MCE is supported in recent Intel CPUs,
> > where some hardware error such as some memory error can be reported
> > without PCC (processor context corrupted). To recover from such MCE,
> > the corresponding memory will be unmapped, and all processes accessing
> > the memory will be killed via SIGBUS.
> >
> > For KVM, if QEMU/KVM is killed, all guest processes will be killed
> > too. So we relay SIGBUS from host OS to guest system via a UCR MCE
> > injection. Then guest OS can isolate corresponding memory and kill
> > necessary guest processes only. SIGBUS sent to main thread (not VCPU
> > threads) will be broadcast to all VCPU threads as UCR MCE.
> >
> >    
> Won't the guest be confused by the broadcast?  How does real hardware work?

We do broadcasting to follow the hardware behavior.

> > +static void sigbus_handler(int n, struct signalfd_siginfo *siginfo, void *ctx)
> > +{
> > +    if (siginfo->ssi_code == BUS_MCEERR_AO) {
> > +        uint64_t status;
> > +        unsigned long paddr;
> > +        CPUState *cenv;
> > +
> > +        /* Hope we are lucky for AO MCE */
> > +        if (kvm_addr_userspace_to_phys((unsigned long)siginfo->ssi_addr,
> > +&paddr)) {
> > +            fprintf(stderr, "Hardware memory error for memory used by "
> > +                    "QEMU itself instead of guest system!: %llx\n",
> > +                    (unsigned long long)siginfo->ssi_addr);
> > +            return;
> > +        }
> > +        status = MCI_STATUS_VAL | MCI_STATUS_UC | MCI_STATUS_EN
> > +            | MCI_STATUS_MISCV | MCI_STATUS_ADDRV | MCI_STATUS_S
> > +            | 0xc0;
> > +        kvm_inject_x86_mce(first_cpu, 9, status,
> > +                           MCG_STATUS_MCIP | MCG_STATUS_RIPV, paddr,
> > +                           (MCM_ADDR_PHYS<<  6) | 0xc);
> >    
> 
> This is a vcpu ioctl, yes?  if so it must be called from the vcpu thread.

No. kvm_inject_x86_mce will call on_vcpu to do the real vcpu ioctl.

Best Regards,
Huang Ying