linux-kernel - [PATCH 6.0 176/862] KVM: nVMX: Dont propagate vmcs12s PERF_GLOBAL

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Message-Id: <20221019083257.733482554@linuxfoundation.org>
Date:   Wed, 19 Oct 2022 10:24:23 +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, Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 6.0 176/862] KVM: nVMX: Dont propagate vmcs12s PERF_GLOBAL_CTRL settings to vmcs02

From: Sean Christopherson <seanjc@...gle.com>

commit def9d705c05eab3fdedeb10ad67907513b12038e upstream.

Don't propagate vmcs12's VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL to vmcs02.
KVM doesn't disallow L1 from using VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL
even when KVM itself doesn't use the control, e.g. due to the various
CPU errata that where the MSR can be corrupted on VM-Exit.

Preserve KVM's (vmcs01) setting to hopefully avoid having to toggle the
bit in vmcs02 at a later point.  E.g. if KVM is loading PERF_GLOBAL_CTRL
when running L1, then odds are good KVM will also load the MSR when
running L2.

Fixes: 8bf00a529967 ("KVM: VMX: add support for switching of PERF_GLOBAL_CTRL")
Cc: stable@...r.kernel.org
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Link: https://lore.kernel.org/r/20220830133737.1539624-18-vkuznets@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/kvm/vmx/nested.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2328,9 +2328,14 @@ static void prepare_vmcs02_early(struct
 	 * are emulated by vmx_set_efer() in prepare_vmcs02(), but speculate
 	 * on the related bits (if supported by the CPU) in the hope that
 	 * we can avoid VMWrites during vmx_set_efer().
+	 *
+	 * Similarly, take vmcs01's PERF_GLOBAL_CTRL in the hope that if KVM is
+	 * loading PERF_GLOBAL_CTRL via the VMCS for L1, then KVM will want to
+	 * do the same for L2.
 	 */
 	exec_control = __vm_entry_controls_get(vmcs01);
-	exec_control |= vmcs12->vm_entry_controls;
+	exec_control |= (vmcs12->vm_entry_controls &
+			 ~VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL);
 	exec_control &= ~(VM_ENTRY_IA32E_MODE | VM_ENTRY_LOAD_IA32_EFER);
 	if (cpu_has_load_ia32_efer()) {
 		if (guest_efer & EFER_LMA)