linux-kernel - [PATCH V3 3/4] KVM: Add tlb remote flush callback in kvm_x86

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Message-ID: <20180719083946.121493-4-Tianyu.Lan@microsoft.com>
Date:   Thu, 19 Jul 2018 08:40:17 +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>,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>
Subject: [PATCH V3 3/4] KVM: Add tlb remote flush callback in kvm_x86_ops.

This patch is to provide a way for platforms to register hv 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>
---
Change since v2:
       Rename kvm_arch_hv_flush_remote_tlb with kvm_arch_flush_remote_tlb
       Rename kvm_x86_ops->hv_tlb_remote_flush with kvm_x86_ops->tlb_remote_flush
       Fix issue that ignore updating tlbs_dirty during calling kvm_arch_flush_remote_tlbs()
Change since v1:
       Add kvm_arch_hv_flush_remote_tlb() to avoid compilation issue
for non-x86 platform.
---
 arch/x86/include/asm/kvm_host.h | 11 +++++++++++
 include/linux/kvm_host.h        |  7 +++++++
 virt/kvm/kvm_main.c             |  3 ++-
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c13cd28d9d1b..76e806bc4ef8 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);
@@ -1117,6 +1118,16 @@ static inline void kvm_arch_free_vm(struct kvm *kvm)
 	return kvm_x86_ops->vm_free(kvm);
 }
 
+#define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLB
+static inline int kvm_arch_flush_remote_tlb(struct kvm *kvm)
+{
+	if (kvm_x86_ops->tlb_remote_flush &&
+	    !kvm_x86_ops->tlb_remote_flush(kvm))
+		return 0;
+	else
+		return -EFAULT;
+}
+
 int kvm_mmu_module_init(void);
 void kvm_mmu_module_exit(void);
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 4ee7bc548a83..0781d94200df 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -827,6 +827,13 @@ static inline void kvm_arch_free_vm(struct kvm *kvm)
 }
 #endif
 
+#ifndef __KVM_HAVE_ARCH_FLUSH_REMOTE_TLB
+static inline int kvm_arch_flush_remote_tlb(struct kvm *kvm)
+{
+	return -EFAULT;
+}
+#endif
+
 #ifdef __KVM_HAVE_ARCH_NONCOHERENT_DMA
 void kvm_arch_register_noncoherent_dma(struct kvm *kvm);
 void kvm_arch_unregister_noncoherent_dma(struct kvm *kvm);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8b47507faab5..1a13cdb2822b 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -273,7 +273,8 @@ void kvm_flush_remote_tlbs(struct kvm *kvm)
 	 * kvm_make_all_cpus_request() reads vcpu->mode. We reuse that
 	 * barrier here.
 	 */
-	if (kvm_make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH))
+	if (!kvm_arch_flush_remote_tlb(kvm)
+	    || kvm_make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH))
 		++kvm->stat.remote_tlb_flush;
 	cmpxchg(&kvm->tlbs_dirty, dirty_count, 0);
 }
-- 
2.14.3