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KVM: Don't spin on virt instruction faults during reboot

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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>
This commit is contained in:
Avi Kivity 2010-12-02 17:52:50 +02:00
parent 4cc703100b
commit b7c4145ba2
2 changed files with 10 additions and 11 deletions
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8
arch/x86/include/asm/kvm_host.h
View File

@ -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" \

13
virt/kvm/kvm_main.c
View File

@ -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)