Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[sfrench/cifs-2.6.git] / Documentation / virt / kvm / api.txt

diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
index 136f1eef3712d3b3205c43a61b4c6e78c69d3e28..4833904d32a5aae880186f47266738cdcd44989d 100644 (file)
--- a/Documentation/virt/kvm/api.txt
+++ b/Documentation/virt/kvm/api.txt
@@ -5309,3 +5309,16 @@ Architectures: x86
 This capability indicates that KVM supports paravirtualized Hyper-V IPI send
 hypercalls:
 HvCallSendSyntheticClusterIpi, HvCallSendSyntheticClusterIpiEx.
+8.21 KVM_CAP_HYPERV_DIRECT_TLBFLUSH
+
+Architecture: x86
+
+This capability indicates that KVM running on top of Hyper-V hypervisor
+enables Direct TLB flush for its guests meaning that TLB flush
+hypercalls are handled by Level 0 hypervisor (Hyper-V) bypassing KVM.
+Due to the different ABI for hypercall parameters between Hyper-V and
+KVM, enabling this capability effectively disables all hypercall
+handling by KVM (as some KVM hypercall may be mistakenly treated as TLB
+flush hypercalls by Hyper-V) so userspace should disable KVM identification
+in CPUID and only exposes Hyper-V identification. In this case, guest
+thinks it's running on Hyper-V and only use Hyper-V hypercalls.