[PATCH V2 2/5] KVM: Add tlb remote flush callback in kvm_x86_ops.

[Tianyu Lan <Tianyu.Lan@microsoft.com>]

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@microsoft.com>
---
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             | 11 ++++++++++-
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c13cd28d9d1b..d89e4204816c 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  (*hv_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_HV_FLUSH_REMOTE_TLB
+static inline int kvm_arch_hv_flush_remote_tlb(struct kvm *kvm)
+{
+	if (kvm_x86_ops->hv_tlb_remote_flush &&
+	    !kvm_x86_ops->hv_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..0c2c36cb041b 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_HV_FLUSH_REMOTE_TLB
+static inline int kvm_arch_hv_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..c2b5e3273848 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -256,11 +256,20 @@ 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 kvm_arch_hv_tlb_remote first and go back old way when
+	 * return failure.
+	 */
+	if (!kvm_arch_hv_flush_remote_tlb(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