KVM: Let host know whether the guest can handle async PF in non-userspace context.

If guest can detect that it runs in non-preemptable context it can
handle async PFs at any time, so let host know that it can send async
PF even if guest cpu is not in userspace.

Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/Documentation/kvm/msr.txt b/Documentation/kvm/msr.txt
index e67b4a8783df..d079aed27e03 100644
--- a/Documentation/kvm/msr.txt
+++ b/Documentation/kvm/msr.txt
@@ -154,9 +154,10 @@ MSR_KVM_SYSTEM_TIME: 0x12
 MSR_KVM_ASYNC_PF_EN: 0x4b564d02
         data: Bits 63-6 hold 64-byte aligned physical address of a
         64 byte memory area which must be in guest RAM and must be
-        zeroed. Bits 5-1 are reserved and should be zero. Bit 0 is 1
+        zeroed. Bits 5-2 are reserved and should be zero. Bit 0 is 1
         when asynchronous page faults are enabled on the vcpu 0 when
-        disabled.
+        disabled. Bit 2 is 1 if asynchronous page faults can be injected
+        when vcpu is in cpl == 0.
 
         First 4 byte of 64 byte memory location will be written to by
         the hypervisor at the time of asynchronous page fault (APF)