On 09/22/2009 04:12 AM, Huang Ying wrote:
On Mon, 2009-09-21 at 18:08 +0800, Avi Kivity wrote:
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:
Maybe we can just add necessary fields to struct qemu_signalfd_siginfo.
But this may be not portable.
That is what I did.
+
+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?
Because SIGBUS is blocked, I think the signal handler will not be called
directly, but from sigfd_handler.
Yes, I think so too.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
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