linux-kernel - [PATCH v3 1/5] KVM: VMX: Introduce generic fastpath handler

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Date:   Fri, 24 Apr 2020 14:22:40 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Haiwei Li <lihaiwei@...cent.com>
Subject: [PATCH v3 1/5] KVM: VMX: Introduce generic fastpath handler

From: Wanpeng Li <wanpengli@...cent.com>

Introduce generic fastpath handler to handle MSR fastpath, VMX-preemption 
timer fastpath etc. In addition, we can't observe benefit from single 
target IPI fastpath when APICv is disabled, let's just enable IPI and 
Timer fastpath when APICv is enabled for now.

Tested-by: Haiwei Li <lihaiwei@...cent.com>
Cc: Haiwei Li <lihaiwei@...cent.com>
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/vmx/vmx.c          | 25 ++++++++++++++++++++-----
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f26df2c..6397723 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -188,6 +188,7 @@ enum {
 enum exit_fastpath_completion {
 	EXIT_FASTPATH_NONE,
 	EXIT_FASTPATH_SKIP_EMUL_INS,
+	EXIT_FASTPATH_CONT_RUN,
 };
 
 struct x86_emulate_ctxt;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 766303b..f1f6638 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6559,6 +6559,20 @@ void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp)
 	}
 }
 
+static enum exit_fastpath_completion vmx_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
+{
+	if (!is_guest_mode(vcpu) && vcpu->arch.apicv_active) {
+		switch (to_vmx(vcpu)->exit_reason) {
+		case EXIT_REASON_MSR_WRITE:
+			return handle_fastpath_set_msr_irqoff(vcpu);
+		default:
+			return EXIT_FASTPATH_NONE;
+		}
+	}
+
+	return EXIT_FASTPATH_NONE;
+}
+
 bool __vmx_vcpu_run(struct vcpu_vmx *vmx, unsigned long *regs, bool launched);
 
 static enum exit_fastpath_completion vmx_vcpu_run(struct kvm_vcpu *vcpu)
@@ -6567,6 +6581,7 @@ static enum exit_fastpath_completion vmx_vcpu_run(struct kvm_vcpu *vcpu)
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	unsigned long cr3, cr4;
 
+cont_run:
 	/* Record the guest's net vcpu time for enforced NMI injections. */
 	if (unlikely(!enable_vnmi &&
 		     vmx->loaded_vmcs->soft_vnmi_blocked))
@@ -6733,17 +6748,17 @@ static enum exit_fastpath_completion vmx_vcpu_run(struct kvm_vcpu *vcpu)
 	if (unlikely(vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY))
 		return EXIT_FASTPATH_NONE;
 
-	if (!is_guest_mode(vcpu) && vmx->exit_reason == EXIT_REASON_MSR_WRITE)
-		exit_fastpath = handle_fastpath_set_msr_irqoff(vcpu);
-	else
-		exit_fastpath = EXIT_FASTPATH_NONE;
-
 	vmx->loaded_vmcs->launched = 1;
 	vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);
 
 	vmx_recover_nmi_blocking(vmx);
 	vmx_complete_interrupts(vmx);
 
+	exit_fastpath = vmx_exit_handlers_fastpath(vcpu);
+	/* static call is better with retpolines */
+	if (exit_fastpath == EXIT_FASTPATH_CONT_RUN)
+		goto cont_run;
+
 	return exit_fastpath;
 }
 
-- 
2.7.4