linux-kernel - [PATCH 2/2] KVM: x86/mmu: Move filling of Hyper-V's TLB range struct into Hyper-V code

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Date:   Tue,  4 Apr 2023 17:31:33 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        David Matlack <dmatlack@...gle.com>
Subject: [PATCH 2/2] KVM: x86/mmu: Move filling of Hyper-V's TLB range struct
 into Hyper-V code

Refactor Hyper-V's range-based TLB flushing API to take a gfn+nr_pages
pair instead of a struct, and bury said struct in Hyper-V specific code.

Passing along two params generates much better code for the common case
where KVM is _not_ running on Hyper-V, as forwarding the flush on to
Hyper-V's hv_flush_remote_tlbs_range() from kvm_flush_remote_tlbs_range()
becomes a tail call.

Cc: David Matlack <dmatlack@...gle.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/include/asm/kvm_host.h |  9 ++-------
 arch/x86/kvm/kvm_onhyperv.c     | 24 ++++++++++++++++++++----
 arch/x86/kvm/kvm_onhyperv.h     |  2 +-
 arch/x86/kvm/mmu/mmu.c          |  8 ++------
 4 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index ec22101410ee..09eb37853cb1 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -482,11 +482,6 @@ struct kvm_mmu {
 	u64 pdptrs[4]; /* pae */
 };
 
-struct kvm_tlb_range {
-	u64 start_gfn;
-	u64 pages;
-};
-
 enum pmc_type {
 	KVM_PMC_GP = 0,
 	KVM_PMC_FIXED,
@@ -1589,8 +1584,8 @@ struct kvm_x86_ops {
 	void (*flush_tlb_all)(struct kvm_vcpu *vcpu);
 	void (*flush_tlb_current)(struct kvm_vcpu *vcpu);
 	int  (*flush_remote_tlbs)(struct kvm *kvm);
-	int  (*flush_remote_tlbs_range)(struct kvm *kvm,
-					struct kvm_tlb_range *range);
+	int  (*flush_remote_tlbs_range)(struct kvm *kvm, gfn_t gfn,
+					gfn_t nr_pages);
 
 	/*
 	 * Flush any TLB entries associated with the given GVA.
diff --git a/arch/x86/kvm/kvm_onhyperv.c b/arch/x86/kvm/kvm_onhyperv.c
index 2e2d08da8a3f..ded0bd688c65 100644
--- a/arch/x86/kvm/kvm_onhyperv.c
+++ b/arch/x86/kvm/kvm_onhyperv.c
@@ -10,17 +10,22 @@
 #include "hyperv.h"
 #include "kvm_onhyperv.h"
 
+struct kvm_hv_tlb_range {
+	u64 start_gfn;
+	u64 pages;
+};
+
 static int kvm_fill_hv_flush_list_func(struct hv_guest_mapping_flush_list *flush,
 		void *data)
 {
-	struct kvm_tlb_range *range = data;
+	struct kvm_hv_tlb_range *range = data;
 
 	return hyperv_fill_flush_guest_mapping_list(flush, range->start_gfn,
 			range->pages);
 }
 
 static inline int hv_remote_flush_root_tdp(hpa_t root_tdp,
-					   struct kvm_tlb_range *range)
+					   struct kvm_hv_tlb_range *range)
 {
 	if (range)
 		return hyperv_flush_guest_mapping_range(root_tdp,
@@ -29,7 +34,8 @@ static inline int hv_remote_flush_root_tdp(hpa_t root_tdp,
 		return hyperv_flush_guest_mapping(root_tdp);
 }
 
-int hv_flush_remote_tlbs_range(struct kvm *kvm, struct kvm_tlb_range *range)
+static int __hv_flush_remote_tlbs_range(struct kvm *kvm,
+					struct kvm_hv_tlb_range *range)
 {
 	struct kvm_arch *kvm_arch = &kvm->arch;
 	struct kvm_vcpu *vcpu;
@@ -85,11 +91,21 @@ int hv_flush_remote_tlbs_range(struct kvm *kvm, struct kvm_tlb_range *range)
 	spin_unlock(&kvm_arch->hv_root_tdp_lock);
 	return ret;
 }
+
+int hv_flush_remote_tlbs_range(struct kvm *kvm, gfn_t start_gfn, gfn_t nr_pages)
+{
+	struct kvm_hv_tlb_range range = {
+		.start_gfn = start_gfn,
+		.pages = nr_pages,
+	};
+
+	return __hv_flush_remote_tlbs_range(kvm, &range);
+}
 EXPORT_SYMBOL_GPL(hv_flush_remote_tlbs_range);
 
 int hv_flush_remote_tlbs(struct kvm *kvm)
 {
-	return hv_flush_remote_tlbs_range(kvm, NULL);
+	return __hv_flush_remote_tlbs_range(kvm, NULL);
 }
 EXPORT_SYMBOL_GPL(hv_flush_remote_tlbs);
 
diff --git a/arch/x86/kvm/kvm_onhyperv.h b/arch/x86/kvm/kvm_onhyperv.h
index 55d7fcb84cc1..ff127d313242 100644
--- a/arch/x86/kvm/kvm_onhyperv.h
+++ b/arch/x86/kvm/kvm_onhyperv.h
@@ -7,7 +7,7 @@
 #define __ARCH_X86_KVM_KVM_ONHYPERV_H__
 
 #if IS_ENABLED(CONFIG_HYPERV)
-int hv_flush_remote_tlbs_range(struct kvm *kvm, struct kvm_tlb_range *range);
+int hv_flush_remote_tlbs_range(struct kvm *kvm, gfn_t gfn, gfn_t nr_pages);
 int hv_flush_remote_tlbs(struct kvm *kvm);
 void hv_track_root_tdp(struct kvm_vcpu *vcpu, hpa_t root_tdp);
 #else /* !CONFIG_HYPERV */
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 7654be48ff69..a7adbac0855c 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -278,15 +278,11 @@ static inline bool kvm_available_flush_remote_tlbs_range(void)
 void kvm_flush_remote_tlbs_range(struct kvm *kvm, gfn_t start_gfn,
 				 gfn_t nr_pages)
 {
-	struct kvm_tlb_range range;
 	int ret = -EOPNOTSUPP;
 
-	range.start_gfn = start_gfn;
-	range.pages = nr_pages;
-
 	if (kvm_x86_ops.flush_remote_tlbs_range)
-		ret = static_call(kvm_x86_flush_remote_tlbs_range)(kvm, &range);
-
+		ret = static_call(kvm_x86_flush_remote_tlbs_range)(kvm, start_gfn,
+								   nr_pages);
 	if (ret)
 		kvm_flush_remote_tlbs(kvm);
 }
-- 
2.40.0.348.gf938b09366-goog