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

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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>
This commit is contained in:
Jon Doron 2020-07-17 15:52:38 +03:00 committed by Paolo Bonzini
parent f40a4b0512
commit 99b48ecc8e
1 changed files with 1 additions and 0 deletions
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arch/x86/kvm/hyperv.c
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@ -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;
}