Waba wrote:
It took me a while, but I figured it out... nearly!
Everything SIGILLs after the fs-root service is started. Its start
method does several things, but the problematic bit is replacing the
libc with an optimised version (namely, /usr/lib/libc/libc_hwcap1.so.1,
which makes use of the SSE, MMX, CMOV, SEP and FPU instruction sets
according to file(1)).
All these flags are indeed advertised in the CPUID (isainfo -v: sse2 sse
fxsr mmx cmov sep cx8 tsc fpu)). If the amd_sysc bit had been present,
the hwcap2 version would have been selected by moe(1), I guess (adds
SSE2 support and replaces SEP by AMD_SYSC).
Disabling the libc replacement in /lib/svc/method/fs-root entirely
workarounds the problem.
Further investigating, I tricked ls(1) into using the optimised libc
through LD_LIBRARY_PATH and obtained a core. mdb(1) told me that the
culprit was hiding at libc`memset+0x74. And finally, dis(1) revealed
that the faulty instruction is "movups (%esp), %xmm0", a SSE feature.
The %xmm0 register is apparently for storage purposes only, as the only
instructions used to access it are movups, movntps and movaps.
At this point I hope that it makes a lot of sense to you, because I
have no idea why it works fine on Avi's Opteron, etc.
Let me know if you need any additional debugging.
Let's look at the control registers at the time of the SIGILL. Can you
reproduce the error with the attached patch and send dmesg?
--
error compiling committee.c: too many arguments to function
Index: svm.c
===================================================================
--- svm.c (revision 4412)
+++ svm.c (working copy)
@@ -481,7 +481,7 @@
INTERCEPT_DR5_MASK |
INTERCEPT_DR7_MASK;
- control->intercept_exceptions = 1 << PF_VECTOR;
+ control->intercept_exceptions = (1 << PF_VECTOR) | (1 << UD_VECTOR);
control->intercept = (1ULL << INTERCEPT_INTR) |
@@ -1247,6 +1247,15 @@
return 1;
}
+static int ud_interception(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+ printk(KERN_ERR "#ud: cr0 %lx (%llx) cr4 %lx (%llx)\n",
+ vcpu->cr0, vcpu->svm->vmcb->save.cr0,
+ vcpu->cr4, vcpu->svm->vmcb->save.cr4);
+ run->exit_reason = KVM_EXIT_SHUTDOWN;
+ return 0;
+}
+
static int (*svm_exit_handlers[])(struct kvm_vcpu *vcpu,
struct kvm_run *kvm_run) = {
[SVM_EXIT_READ_CR0] = emulate_on_interception,
@@ -1267,6 +1276,7 @@
[SVM_EXIT_WRITE_DR5] = emulate_on_interception,
[SVM_EXIT_WRITE_DR7] = emulate_on_interception,
[SVM_EXIT_EXCP_BASE + PF_VECTOR] = pf_interception,
+ [SVM_EXIT_EXCP_BASE + UD_VECTOR] = ud_interception,
[SVM_EXIT_INTR] = nop_on_interception,
[SVM_EXIT_NMI] = nop_on_interception,
[SVM_EXIT_SMI] = nop_on_interception,
-------------------------------------------------------------------------
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