Commit 8d68bad6 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Paolo Bonzini
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KVM: nVMX: Filter out all unsupported controls when eVMCS was activated 



Windows Server 2022 with Hyper-V role enabled failed to boot on KVM when
enlightened VMCS is advertised. Debugging revealed there are two exposed
secondary controls it is not happy with: SECONDARY_EXEC_ENABLE_VMFUNC and
SECONDARY_EXEC_SHADOW_VMCS. These controls are known to be unsupported,
as there are no corresponding fields in eVMCSv1 (see the comment above
EVMCS1_UNSUPPORTED_2NDEXEC definition).

Previously, commit 31de3d25 ("x86/kvm/hyper-v: move VMX controls
sanitization out of nested_enable_evmcs()") introduced the required
filtering mechanism for VMX MSRs but for some reason put only known
to be problematic (and not full EVMCS1_UNSUPPORTED_* lists) controls
there.

Note, Windows Server 2022 seems to have gained some sanity check for VMX
MSRs: it doesn't even try to launch a guest when there's something it
doesn't like, nested_evmcs_check_controls() mechanism can't catch the
problem.

Let's be bold this time and instead of playing whack-a-mole just filter out
all unsupported controls from VMX MSRs.

Fixes: 31de3d25 ("x86/kvm/hyper-v: move VMX controls sanitization out of nested_enable_evmcs()")
Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210907163530.110066-1-vkuznets@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 0bbc2ca8

arch/x86/kvm/vmx/evmcs.c

+9 −3
Original line number Diff line number Diff line
@@ -353,14 +353,20 @@ void nested_evmcs_filter_control_msr(u32 msr_index, u64 *pdata) 
	switch (msr_index) {

	case MSR_IA32_VMX_EXIT_CTLS:

	case MSR_IA32_VMX_TRUE_EXIT_CTLS:

		ctl_high &= ~VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;

		ctl_high &= ~EVMCS1_UNSUPPORTED_VMEXIT_CTRL;

		break;

	case MSR_IA32_VMX_ENTRY_CTLS:

	case MSR_IA32_VMX_TRUE_ENTRY_CTLS:

		ctl_high &= ~VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;

		ctl_high &= ~EVMCS1_UNSUPPORTED_VMENTRY_CTRL;

		break;

	case MSR_IA32_VMX_PROCBASED_CTLS2:

		ctl_high &= ~SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;

		ctl_high &= ~EVMCS1_UNSUPPORTED_2NDEXEC;

		break;

	case MSR_IA32_VMX_PINBASED_CTLS:

		ctl_high &= ~EVMCS1_UNSUPPORTED_PINCTRL;

		break;

	case MSR_IA32_VMX_VMFUNC:

		ctl_low &= ~EVMCS1_UNSUPPORTED_VMFUNC;

		break;

	}

arch/x86/kvm/vmx/vmx.c

+5 −4
Original line number Diff line number Diff line
@@ -1837,10 +1837,11 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) 
				    &msr_info->data))

			return 1;

		/*

		 * Enlightened VMCS v1 doesn't have certain fields, but buggy

		 * Hyper-V versions are still trying to use corresponding

		 * features when they are exposed. Filter out the essential

		 * minimum.

		 * Enlightened VMCS v1 doesn't have certain VMCS fields but

		 * instead of just ignoring the features, different Hyper-V

		 * versions are either trying to use them and fail or do some

		 * sanity checking and refuse to boot. Filter all unsupported

		 * features out.

		 */

		if (!msr_info->host_initiated &&

		    vmx->nested.enlightened_vmcs_enabled)