path: root/include
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authorRoman Kagan <rkagan@virtuozzo.com>2017-06-22 16:51:01 +0300
committerRadim Krčmář <rkrcmar@redhat.com>2017-07-13 17:41:04 +0200
commitefc479e6900c22bad9a2b649d13405ed9cde2d53 (patch)
tree517b287129af96017f2aad22e7dd352ce725cbe6 /include
parenta826faf108e2d855929342268e68c43ba667379a (diff)
kvm: x86: hyperv: add KVM_CAP_HYPERV_SYNIC2
There is a flaw in the Hyper-V SynIC implementation in KVM: when message page or event flags page is enabled by setting the corresponding msr, KVM zeroes it out. This is problematic because on migration the corresponding MSRs are loaded on the destination, so the content of those pages is lost. This went unnoticed so far because the only user of those pages was in-KVM hyperv synic timers, which could continue working despite that zeroing. Newer QEMU uses those pages for Hyper-V VMBus implementation, and zeroing them breaks the migration. Besides, in newer QEMU the content of those pages is fully managed by QEMU, so zeroing them is undesirable even when writing the MSRs from the guest side. To support this new scheme, introduce a new capability, KVM_CAP_HYPERV_SYNIC2, which, when enabled, makes sure that the synic pages aren't zeroed out in KVM. Signed-off-by: Roman Kagan <rkagan@virtuozzo.com> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Diffstat (limited to 'include')
1 files changed, 1 insertions, 0 deletions
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index ebd604c222d8..38b2cfbc8112 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -927,6 +927,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_PPC_FWNMI 146
+#define KVM_CAP_HYPERV_SYNIC2 148

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