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From:   Tianyu Lan <Tianyu.Lan@microsoft.com>
CC:     Tianyu Lan <Tianyu.Lan@microsoft.com>,
        "pbonzini@redhat.com" <pbonzini@redhat.com>,
        "rkrcmar@redhat.com" <rkrcmar@redhat.com>,
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        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        KY Srinivasan <kys@microsoft.com>,
        "vkuznets@redhat.com" <vkuznets@redhat.com>
Subject: [RFC Patch 2/3] KVM: Add tlb remote flush callback in kvm_x86_ops.
Thread-Topic: [RFC Patch 2/3] KVM: Add tlb remote flush callback in
 kvm_x86_ops.
Thread-Index: AQHT++OaghvAztGQfkKjrBIBb1LvJQ==
Date:   Mon, 4 Jun 2018 09:08:28 +0000
Message-ID: <20180604090749.489-3-Tianyu.Lan@microsoft.com>
References: <20180604090749.489-1-Tianyu.Lan@microsoft.com>
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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@microsoft.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_hos=
t.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);
=20
 	void (*tlb_flush)(struct kvm_vcpu *vcpu, bool invalidate_gpa);
+	int  (*tlb_remote_flush)(struct kvm *kvm);
=20
 	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, unsig=
ned 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 =3D smp_load_acquire(&kvm->tlbs_dirty);
+	dirty_count =3D smp_load_acquire(&kvm->tlbs_dirty);
=20
 	/*
 	 * We want to publish modifications to the page tables before reading
--=20
2.14.3