linux-kernel - [RFC Patch 2/3] KVM: Add tlb remote flush callback in kvm_x86

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Message-ID: <20180604090749.489-3-Tianyu.Lan@microsoft.com>
Date:   Mon, 4 Jun 2018 09:08:28 +0000
From:   Tianyu Lan <Tianyu.Lan@...rosoft.com>
To:     unlisted-recipients:; (no To-header on input)
CC:     Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>
Subject: [RFC Patch 2/3] KVM: Add tlb remote flush callback in kvm_x86_ops.

This patch is to provide a way for platforms to register tlb remote flush
callback and this helps to optimize operation of tlb flush among vcpus for
nested virtualization case.

Signed-off-by: Lan Tianyu <Tianyu.Lan@...rosoft.com>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 virt/kvm/kvm_main.c             | 12 +++++++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 0ebe659f2802..aaad43916f9d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -973,6 +973,7 @@ struct kvm_x86_ops {
 	void (*set_rflags)(struct kvm_vcpu *vcpu, unsigned long rflags);
 
 	void (*tlb_flush)(struct kvm_vcpu *vcpu, bool invalidate_gpa);
+	int  (*tlb_remote_flush)(struct kvm *kvm);
 
 	void (*run)(struct kvm_vcpu *vcpu);
 	int (*handle_exit)(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index c5f6a552e486..31e2b54c6049 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -251,11 +251,21 @@ bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
 #ifndef CONFIG_HAVE_KVM_ARCH_TLB_FLUSH_ALL
 void kvm_flush_remote_tlbs(struct kvm *kvm)
 {
+	long dirty_count;
+
+	/*
+	 * Call tlb_remote_flush first and go back old way when
+	 * return failure.
+	 */
+	if (kvm_x86_ops->tlb_remote_flush &&
+	    !kvm_x86_ops->tlb_remote_flush(kvm))
+		return;
+
 	/*
 	 * Read tlbs_dirty before setting KVM_REQ_TLB_FLUSH in
 	 * kvm_make_all_cpus_request.
 	 */
-	long dirty_count = smp_load_acquire(&kvm->tlbs_dirty);
+	dirty_count = smp_load_acquire(&kvm->tlbs_dirty);
 
 	/*
 	 * We want to publish modifications to the page tables before reading
-- 
2.14.3