linux-kernel - [PATCH 5.18 0038/1095] KVM: nVMX: Always enable TSC scaling for L2 when it was enabled for L1

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Message-Id: <20220815180430.975118197@linuxfoundation.org>
Date:   Mon, 15 Aug 2022 19:50:37 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Vitaly Kuznetsov <vkuznets@...hat.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: [PATCH 5.18 0038/1095] KVM: nVMX: Always enable TSC scaling for L2 when it was enabled for L1

From: Vitaly Kuznetsov <vkuznets@...hat.com>

commit 156b9d76e8822f2956c15029acf2d4b171502f3a upstream.

Windows 10/11 guests with Hyper-V role (WSL2) enabled are observed to
hang upon boot or shortly after when a non-default TSC frequency was
set for L1. The issue is observed on a host where TSC scaling is
supported. The problem appears to be that Windows doesn't use TSC
scaling for its guests, even when the feature is advertised, and KVM
filters SECONDARY_EXEC_TSC_SCALING out when creating L2 controls from
L1's VMCS. This leads to L2 running with the default frequency (matching
host's) while L1 is running with an altered one.

Keep SECONDARY_EXEC_TSC_SCALING in secondary exec controls for L2 when
it was set for L1. TSC_MULTIPLIER is already correctly computed and
written by prepare_vmcs02().

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Fixes: d041b5ea93352b ("KVM: nVMX: Enable nested TSC scaling")
Cc: stable@...r.kernel.org
Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
Link: https://lore.kernel.org/r/20220712135009.952805-1-vkuznets@redhat.com
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/kvm/vmx/nested.c |    1 -
 1 file changed, 1 deletion(-)

--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2283,7 +2283,6 @@ static void prepare_vmcs02_early(struct
 				  SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY |
 				  SECONDARY_EXEC_APIC_REGISTER_VIRT |
 				  SECONDARY_EXEC_ENABLE_VMFUNC |
-				  SECONDARY_EXEC_TSC_SCALING |
 				  SECONDARY_EXEC_DESC);

 		if (nested_cpu_has(vmcs12,