KVM: Don't spin on virt instruction faults during reboot
Since vmx blocks INIT signals, we disable virtualization extensions during
reboot. This leads to virtualization instructions faulting; we trap these
faults and spin while the reboot continues.
Unfortunately spinning on a non-preemptible kernel may block a task that
reboot depends on; this causes the reboot to hang.
Fix by skipping over the instruction and hoping for the best.
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 56e45a2..d968cc5 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -786,14 +786,18 @@
* reboot turns off virtualization while processes are running.
* Trap the fault and ignore the instruction if that happens.
*/
-asmlinkage void kvm_handle_fault_on_reboot(void);
+asmlinkage void kvm_spurious_fault(void);
+extern bool kvm_rebooting;
#define __kvm_handle_fault_on_reboot(insn) \
"666: " insn "\n\t" \
+ "668: \n\t" \
".pushsection .fixup, \"ax\" \n" \
"667: \n\t" \
+ "cmpb $0, kvm_rebooting \n\t" \
+ "jne 668b \n\t" \
__ASM_SIZE(push) " $666b \n\t" \
- "jmp kvm_handle_fault_on_reboot \n\t" \
+ "call kvm_spurious_fault \n\t" \
".popsection \n\t" \
".pushsection __ex_table, \"a\" \n\t" \
_ASM_PTR " 666b, 667b \n\t" \