linux-kernel - [PATCH v4 6/8] KVM: VMX: Introduce vmx_msr_bitmap_l01

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: <20211109162835.99475-7-vkuznets@redhat.com>
Date:   Tue,  9 Nov 2021 17:28:33 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4 6/8] KVM: VMX: Introduce vmx_msr_bitmap_l01_changed() helper

In preparation to enabling 'Enlightened MSR Bitmap' feature for Hyper-V
guests move MSR bitmap update tracking to a dedicated helper.

Note: vmx_msr_bitmap_l01_changed() is called when MSR bitmap might be
updated. KVM doesn't check if the bit we're trying to set is already set
(or the bit it's trying to clear is already cleared). Such situations
should not be common and a few false positives should not be a problem.

No functional change intended.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
Reviewed-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/vmx/vmx.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index fc87b6bbd277..1e6bf2cd7be0 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3677,6 +3677,17 @@ void free_vpid(int vpid)
 	spin_unlock(&vmx_vpid_lock);
 }
 
+static void vmx_msr_bitmap_l01_changed(struct vcpu_vmx *vmx)
+{
+	/*
+	 * When KVM is a nested hypervisor on top of Hyper-V and uses
+	 * 'Enlightened MSR Bitmap' feature L0 needs to know that MSR
+	 * bitmap has changed.
+	 */
+	if (static_branch_unlikely(&enable_evmcs))
+		evmcs_touch_msr_bitmap();
+}
+
 void vmx_disable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -3685,8 +3696,7 @@ void vmx_disable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type)
 	if (!cpu_has_vmx_msr_bitmap())
 		return;
 
-	if (static_branch_unlikely(&enable_evmcs))
-		evmcs_touch_msr_bitmap();
+	vmx_msr_bitmap_l01_changed(vmx);
 
 	/*
 	 * Mark the desired intercept state in shadow bitmap, this is needed
@@ -3730,8 +3740,7 @@ void vmx_enable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type)
 	if (!cpu_has_vmx_msr_bitmap())
 		return;
 
-	if (static_branch_unlikely(&enable_evmcs))
-		evmcs_touch_msr_bitmap();
+	vmx_msr_bitmap_l01_changed(vmx);
 
 	/*
 	 * Mark the desired intercept state in shadow bitmap, this is needed
-- 
2.31.1