If async page fault is received by idle task or when preemp_count is
not zero guest cannot reschedule, so make "wait for page" hypercall
and comtinue only after a page is ready.
Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx>
---
arch/x86/kernel/kvm.c | 16 +++++++++++++++-
1 files changed, 15 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 79d291f..1bd8b8d 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -162,10 +162,24 @@ int kvm_handle_pf(struct pt_regs *regs, unsigned long error_code)
switch (reason) {
default:
return 0;
- case KVM_PV_REASON_PAGE_NP:
+ case KVM_PV_REASON_PAGE_NP: {
+ int cpu, idle;
+ cpu = get_cpu();
+ idle = idle_cpu(cpu);
+ put_cpu();
+
+ /*
+ * We cannot reschedule. Wait for page to be ready.
+ */
+ if (idle || preempt_count()) {
+ kvm_hypercall0(KVM_HC_WAIT_FOR_ASYNC_PF);
+ break;
+ }
+
/* real page is missing. */
apf_task_wait(current, token);
break;
+ }
case KVM_PV_REASON_PAGE_READY:
apf_task_wake(token);
break;
--
1.6.3.3
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