Re: [PATCH -v4] QEMU-KVM: MCE: Relay UCR MCE to guest

[Avi Kivity <avi@redhat.com>]

On 09/21/2009 05:43 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.
>
>
>
> --- a/qemu-kvm.c
> +++ b/qemu-kvm.c
> @@ -27,10 +27,23 @@
>   #include<sys/mman.h>
>   #include<sys/ioctl.h>
>   #include<signal.h>
> +#include<sys/signalfd.h>
>    

This causes a build failure, since not all hosts have <sys/signalfd.h>, 
but more importantly:

> +
> +static void sigbus_handler(int n, struct signalfd_siginfo *siginfo, void *ctx)
> +{
>    

Here you accept signalfd_siginfo, while

> +
> +    memset(&action, 0, sizeof(action));
> +    action.sa_flags = SA_SIGINFO;
> +    action.sa_sigaction = (void (*)(int, siginfo_t*, void*))sigbus_handler;
> +    sigaction(SIGBUS,&action, NULL);
> +    prctl(PR_MCE_KILL, 1, 1);
>       return 0;
>    

here you arm the function with something that will send it a siginfo_t.  
So it looks like this is broken if a signal is ever received directly?  
But can this happen due to signalfd?

>   }
>
> @@ -1962,7 +2116,10 @@ static void sigfd_handler(void *opaque)
>           }
>
>           sigaction(info.ssi_signo, NULL,&action);
> -        if (action.sa_handler)
> +        if ((action.sa_flags&  SA_SIGINFO)&&  action.sa_sigaction)
> +            action.sa_sigaction(info.ssi_signo,
> +                                (siginfo_t *)&info, NULL);
> +	else if (action.sa_handler)
>               action.sa_handler(info.ssi_signo);
>    

The whole "extract handler from sigaction and call it" was a hack.


-- 
error compiling committee.c: too many arguments to function