Commit b7c4145b authored by Avi Kivity's avatar Avi Kivity

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
...@@ -786,14 +786,18 @@ enum { ...@@ -786,14 +786,18 @@ enum {
* reboot turns off virtualization while processes are running. * reboot turns off virtualization while processes are running.
* Trap the fault and ignore the instruction if that happens. * 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) \ #define __kvm_handle_fault_on_reboot(insn) \
"666: " insn "\n\t" \ "666: " insn "\n\t" \
"668: \n\t" \
".pushsection .fixup, \"ax\" \n" \ ".pushsection .fixup, \"ax\" \n" \
"667: \n\t" \ "667: \n\t" \
"cmpb $0, kvm_rebooting \n\t" \
"jne 668b \n\t" \
__ASM_SIZE(push) " $666b \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" \ ".popsection \n\t" \
".pushsection __ex_table, \"a\" \n\t" \ ".pushsection __ex_table, \"a\" \n\t" \
_ASM_PTR " 666b, 667b \n\t" \ _ASM_PTR " 666b, 667b \n\t" \
......
...@@ -90,7 +90,8 @@ static void hardware_disable_all(void); ...@@ -90,7 +90,8 @@ static void hardware_disable_all(void);
static void kvm_io_bus_destroy(struct kvm_io_bus *bus); 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; static bool largepages_enabled = true;
...@@ -2171,18 +2172,12 @@ static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val, ...@@ -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. */ /* Fault while not rebooting. We want the trace. */
BUG(); 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, static int kvm_reboot(struct notifier_block *notifier, unsigned long val,
void *v) void *v)
......
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