From dab4b911a5327859bb8f969249c6978c26cd4853 Mon Sep 17 00:00:00 2001
From: Jan Kiszka <jan.kiszka@web.de>
Date: Sun, 6 Dec 2009 18:24:15 +0100
Subject: KVM: x86: Extend KVM_SET_VCPU_EVENTS with selective updates

User space may not want to overwrite asynchronously changing VCPU event
states on write-back. So allow to skip nmi.pending and sipi_vector by
setting corresponding bits in the flags field of kvm_vcpu_events.

[avi: advertise the bits in KVM_GET_VCPU_EVENTS]

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
 Documentation/kvm/api.txt | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

(limited to 'Documentation/kvm')

diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt
index e1a11416102..2811e452f75 100644
--- a/Documentation/kvm/api.txt
+++ b/Documentation/kvm/api.txt
@@ -685,7 +685,7 @@ struct kvm_vcpu_events {
 		__u8 pad;
 	} nmi;
 	__u32 sipi_vector;
-	__u32 flags;   /* must be zero */
+	__u32 flags;
 };
 
 4.30 KVM_SET_VCPU_EVENTS
@@ -701,6 +701,14 @@ vcpu.
 
 See KVM_GET_VCPU_EVENTS for the data structure.
 
+Fields that may be modified asynchronously by running VCPUs can be excluded
+from the update. These fields are nmi.pending and sipi_vector. Keep the
+corresponding bits in the flags field cleared to suppress overwriting the
+current in-kernel state. The bits are:
+
+KVM_VCPUEVENT_VALID_NMI_PENDING - transfer nmi.pending to the kernel
+KVM_VCPUEVENT_VALID_SIPI_VECTOR - transfer sipi_vector
+
 
 5. The kvm_run structure
 
-- 
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