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Commit b7c4145b authored by Avi Kivity's avatar Avi Kivity
Browse files

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: default avatarAvi Kivity <avi@redhat.com>
parent 4cc70310

arch/x86/include/asm/kvm_host.h

+6 −2
Original line number Diff line number Diff line
@@ -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" \

virt/kvm/kvm_main.c

+4 −9
Original line number Diff line number Diff line
@@ -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;
@@ -2171,18 +2172,12 @@ 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)