Commit 99b48ecc authored Jul 17, 2020 by Jon Doron Committed by Paolo Bonzini Aug 10, 2020

x86/kvm/hyper-v: Synic default SCONTROL MSR needs to be enabled



Based on an analysis of the HyperV firmwares (Gen1 and Gen2) it seems
like the SCONTROL is not being set to the ENABLED state as like we have
thought.

Also from a test done by Vitaly Kuznetsov, running a nested HyperV it
was concluded that the first access to the SCONTROL MSR with a read
resulted with the value of 0x1, aka HV_SYNIC_CONTROL_ENABLE.

It's important to note that this diverges from the value states in the
HyperV TLFS of 0.

Signed-off-by: Jon Doron <arilou@gmail.com>
Message-Id: <20200717125238.1103096-2-arilou@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent f40a4b05

arch/x86/kvm/hyperv.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -900,6 +900,7 @@ int kvm_hv_activate_synic(struct kvm_vcpu *vcpu, bool dont_zero_synic_pages)
		kvm_request_apicv_update(vcpu->kvm, false, APICV_INHIBIT_REASON_HYPERV);
		synic->active = true;
		synic->dont_zero_synic_pages = dont_zero_synic_pages;
		synic->control = HV_SYNIC_CONTROL_ENABLE;
		return 0;
		}

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