From: Avi Kivity <a...@redhat.com>
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 <a...@redhat.com>
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e35c43f..cfbcbfa 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -786,14 +786,18 @@ enum {
* 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" \
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index c4ee364..83f5bf6 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -90,7 +90,8 @@ static void hardware_disable_all(void);
static void kvm_io_bus_destroy(struct kvm_io_bus *bus);
-static bool kvm_rebooting;
+bool kvm_rebooting;
+EXPORT_SYMBOL_GPL(kvm_rebooting);
static bool largepages_enabled = true;
@@ -2179,18 +2180,12 @@ static int kvm_cpu_hotplug(struct notifier_block
*notifier, unsigned long val,
}
-asmlinkage void kvm_handle_fault_on_reboot(void)
+asmlinkage void kvm_spurious_fault(void)
{
- if (kvm_rebooting) {
- /* spin while reset goes on */
- local_irq_enable();
- while (true)
- cpu_relax();
- }
/* Fault while not rebooting. We want the trace. */
BUG();
}
-EXPORT_SYMBOL_GPL(kvm_handle_fault_on_reboot);
+EXPORT_SYMBOL_GPL(kvm_spurious_fault);
static int kvm_reboot(struct notifier_block *notifier, unsigned long val,
void *v)
--
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