From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 1/2] KVM: nVMX: Refactor IBPB handling on VMCS switch to genericize code
Date: Wed, 6 May 2020 16:58:49 -0700 [thread overview]
Message-ID: <20200506235850.22600-2-sean.j.christopherson@intel.com> (raw)
In-Reply-To: <20200506235850.22600-1-sean.j.christopherson@intel.com>
Refactor the IPBP handling to effectively move the WARN and comment in
vmx_switch_vmcs() to vmx_vcpu_load_vmcs(). A future patch will give
copy_vmcs02_to_vmcs12_rare() the same treatment.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kvm/vmx/nested.c | 9 +--------
arch/x86/kvm/vmx/vmx.c | 17 +++++++++++++----
arch/x86/kvm/vmx/vmx.h | 3 ++-
3 files changed, 16 insertions(+), 13 deletions(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 20a9edca51fa5..7d1e19149ef46 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -302,15 +302,8 @@ static void vmx_switch_vmcs(struct kvm_vcpu *vcpu, struct loaded_vmcs *vmcs)
cpu = get_cpu();
prev = vmx->loaded_vmcs;
- WARN_ON_ONCE(prev->cpu != cpu || prev->vmcs != per_cpu(current_vmcs, cpu));
vmx->loaded_vmcs = vmcs;
-
- /*
- * This is the same guest from our point of view, so no
- * indirect branch prediction barrier is needed. The L1
- * guest can protect itself with retpolines, IBPB or IBRS.
- */
- vmx_vcpu_load_vmcs(vcpu, cpu, false);
+ vmx_vcpu_load_vmcs(vcpu, cpu, prev);
vmx_sync_vmcs_host_state(vmx, prev);
put_cpu();
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 94f49c5ae89aa..ddbd8fae24927 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1311,10 +1311,12 @@ static void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
pi_set_on(pi_desc);
}
-void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu, bool need_ibpb)
+void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu,
+ struct loaded_vmcs *buddy)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
bool already_loaded = vmx->loaded_vmcs->cpu == cpu;
+ struct vmcs *prev;
if (!already_loaded) {
loaded_vmcs_clear(vmx->loaded_vmcs);
@@ -1333,10 +1335,17 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu, bool need_ibpb)
local_irq_enable();
}
- if (per_cpu(current_vmcs, cpu) != vmx->loaded_vmcs->vmcs) {
+ prev = per_cpu(current_vmcs, cpu);
+ if (prev != vmx->loaded_vmcs->vmcs) {
per_cpu(current_vmcs, cpu) = vmx->loaded_vmcs->vmcs;
vmcs_load(vmx->loaded_vmcs->vmcs);
- if (need_ibpb)
+
+ /*
+ * No indirect branch prediction barrier needed when switching
+ * the active VMCS within a guest, e.g. on nested VM-Enter.
+ * The L1 VMM can protect itself with retpolines, IBPB or IBRS.
+ */
+ if (!buddy || WARN_ON_ONCE(buddy->vmcs != prev))
indirect_branch_prediction_barrier();
}
@@ -1378,7 +1387,7 @@ void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
- vmx_vcpu_load_vmcs(vcpu, cpu, true);
+ vmx_vcpu_load_vmcs(vcpu, cpu, NULL);
vmx_vcpu_pi_load(vcpu, cpu);
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index c6f940ba5d79c..4a6f382b05b49 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -320,7 +320,8 @@ struct kvm_vmx {
};
bool nested_vmx_allowed(struct kvm_vcpu *vcpu);
-void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu, bool need_ibpb);
+void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu,
+ struct loaded_vmcs *buddy);
void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
int allocate_vpid(void);
void free_vpid(int vpid);
--
2.26.0
next prev parent reply other threads:[~2020-05-06 23:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-06 23:58 [PATCH 0/2] KVM: nVMX: Skip IPBP on nested VMCS switch Sean Christopherson
2020-05-06 23:58 ` Sean Christopherson [this message]
2020-05-06 23:58 ` [PATCH 2/2] KVM: nVMX: Skip IPBP when switching between vmcs01 and vmcs02, redux Sean Christopherson
2020-05-07 11:58 ` [PATCH 0/2] KVM: nVMX: Skip IPBP on nested VMCS switch Paolo Bonzini
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