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

Avi Kivity
2009-09-08T06:38:28Z

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?
>
> +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.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.