linux-kernel - [PATCH v4 1/7] KVM: SVM: Make svm_x86_ops globally visible, clean up on-HyperV usage

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Message-ID: <20250919215934.1590410-2-seanjc@google.com>
Date: Fri, 19 Sep 2025 14:59:28 -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, 
	Naveen N Rao <naveen@...nel.org>
Subject: [PATCH v4 1/7] KVM: SVM: Make svm_x86_ops globally visible, clean up
 on-HyperV usage

Make svm_x86_ops globally visible in anticipation of modifying the struct
in avic.c, and clean up the KVM-on-HyperV usage, as declaring _and using_
a local variable in a header that's only defined in one specific .c-file
is all kinds of ugly.

Opportunistically make svm_hv_enable_l2_tlb_flush() local to
svm_onhyperv.c, as the only reason it was visible was due to the
aforementioned shenanigans in svm_onhyperv.h.

Alternatively, svm_x86_ops could be explicitly passed to
svm_hv_hardware_setup() as a parameter.  While that approach is slightly
safer, e.g. avoids "hidden" updates, for better or worse, the Intel side
of KVM has already chosen to expose vt_x86_ops (and vt_init_ops).  Given
that svm_x86_ops is only truly consumed by kvm_ops_update, the odds of a
"hidden" update causing problems are extremely low.  So, absent a strong
reason to rework the VMX/TDX code, make svm_x86_ops visible, as having all
updates use exactly "svm_x86_ops." is advantageous in its own right.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/svm.c          |  2 +-
 arch/x86/kvm/svm/svm.h          |  2 ++
 arch/x86/kvm/svm/svm_onhyperv.c | 28 +++++++++++++++++++++++++++-
 arch/x86/kvm/svm/svm_onhyperv.h | 31 +------------------------------
 4 files changed, 31 insertions(+), 32 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 67f4eed01526..8117d79036bb 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -5032,7 +5032,7 @@ static void *svm_alloc_apic_backing_page(struct kvm_vcpu *vcpu)
 	return page_address(page);
 }
 
-static struct kvm_x86_ops svm_x86_ops __initdata = {
+struct kvm_x86_ops svm_x86_ops __initdata = {
 	.name = KBUILD_MODNAME,
 
 	.check_processor_compatibility = svm_check_processor_compat,
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 5d39c0b17988..1652a868c578 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -52,6 +52,8 @@ extern bool x2avic_enabled;
 extern bool vnmi;
 extern int lbrv;
 
+extern struct kvm_x86_ops svm_x86_ops __initdata;
+
 /*
  * Clean bits in VMCB.
  * VMCB_ALL_CLEAN_MASK might also need to
diff --git a/arch/x86/kvm/svm/svm_onhyperv.c b/arch/x86/kvm/svm/svm_onhyperv.c
index 3971b3ea5d04..a8e78c0e5956 100644
--- a/arch/x86/kvm/svm/svm_onhyperv.c
+++ b/arch/x86/kvm/svm/svm_onhyperv.c
@@ -15,7 +15,7 @@
 #include "kvm_onhyperv.h"
 #include "svm_onhyperv.h"
 
-int svm_hv_enable_l2_tlb_flush(struct kvm_vcpu *vcpu)
+static int svm_hv_enable_l2_tlb_flush(struct kvm_vcpu *vcpu)
 {
 	struct hv_vmcb_enlightenments *hve;
 	hpa_t partition_assist_page = hv_get_partition_assist_page(vcpu);
@@ -35,3 +35,29 @@ int svm_hv_enable_l2_tlb_flush(struct kvm_vcpu *vcpu)
 	return 0;
 }
 
+__init void svm_hv_hardware_setup(void)
+{
+	if (npt_enabled &&
+	    ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB) {
+		pr_info(KBUILD_MODNAME ": Hyper-V enlightened NPT TLB flush enabled\n");
+		svm_x86_ops.flush_remote_tlbs = hv_flush_remote_tlbs;
+		svm_x86_ops.flush_remote_tlbs_range = hv_flush_remote_tlbs_range;
+	}
+
+	if (ms_hyperv.nested_features & HV_X64_NESTED_DIRECT_FLUSH) {
+		int cpu;
+
+		pr_info(KBUILD_MODNAME ": Hyper-V Direct TLB Flush enabled\n");
+		for_each_online_cpu(cpu) {
+			struct hv_vp_assist_page *vp_ap =
+				hv_get_vp_assist_page(cpu);
+
+			if (!vp_ap)
+				continue;
+
+			vp_ap->nested_control.features.directhypercall = 1;
+		}
+		svm_x86_ops.enable_l2_tlb_flush =
+				svm_hv_enable_l2_tlb_flush;
+	}
+}
diff --git a/arch/x86/kvm/svm/svm_onhyperv.h b/arch/x86/kvm/svm/svm_onhyperv.h
index f85bc617ffe4..08f14e6f195c 100644
--- a/arch/x86/kvm/svm/svm_onhyperv.h
+++ b/arch/x86/kvm/svm/svm_onhyperv.h
@@ -13,9 +13,7 @@
 #include "kvm_onhyperv.h"
 #include "svm/hyperv.h"
 
-static struct kvm_x86_ops svm_x86_ops;
-
-int svm_hv_enable_l2_tlb_flush(struct kvm_vcpu *vcpu);
+__init void svm_hv_hardware_setup(void);
 
 static inline bool svm_hv_is_enlightened_tlb_enabled(struct kvm_vcpu *vcpu)
 {
@@ -40,33 +38,6 @@ static inline void svm_hv_init_vmcb(struct vmcb *vmcb)
 		hve->hv_enlightenments_control.msr_bitmap = 1;
 }
 
-static inline __init void svm_hv_hardware_setup(void)
-{
-	if (npt_enabled &&
-	    ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB) {
-		pr_info(KBUILD_MODNAME ": Hyper-V enlightened NPT TLB flush enabled\n");
-		svm_x86_ops.flush_remote_tlbs = hv_flush_remote_tlbs;
-		svm_x86_ops.flush_remote_tlbs_range = hv_flush_remote_tlbs_range;
-	}
-
-	if (ms_hyperv.nested_features & HV_X64_NESTED_DIRECT_FLUSH) {
-		int cpu;
-
-		pr_info(KBUILD_MODNAME ": Hyper-V Direct TLB Flush enabled\n");
-		for_each_online_cpu(cpu) {
-			struct hv_vp_assist_page *vp_ap =
-				hv_get_vp_assist_page(cpu);
-
-			if (!vp_ap)
-				continue;
-
-			vp_ap->nested_control.features.directhypercall = 1;
-		}
-		svm_x86_ops.enable_l2_tlb_flush =
-				svm_hv_enable_l2_tlb_flush;
-	}
-}
-
 static inline void svm_hv_vmcb_dirty_nested_enlightenments(
 		struct kvm_vcpu *vcpu)
 {
-- 
2.51.0.470.ga7dc726c21-goog