linux-kernel - [PATCH v5 4/6] x86: KVM: SVM: use kvm_lock_all_vcpus instead of a custom implementation

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Message-ID: <20250512180407.659015-5-mlevitsk@redhat.com>
Date: Mon, 12 May 2025 14:04:05 -0400
From: Maxim Levitsky <mlevitsk@...hat.com>
To: kvm@...r.kernel.org
Cc: Suzuki K Poulose <suzuki.poulose@....com>,
	Jing Zhang <jingzhangos@...gle.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Sebastian Ott <sebott@...hat.com>,
	Shusen Li <lishusen2@...wei.com>,
	Waiman Long <longman@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-arm-kernel@...ts.infradead.org,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Borislav Petkov <bp@...en8.de>,
	Anup Patel <anup@...infault.org>,
	Will Deacon <will@...nel.org>,
	Palmer Dabbelt <palmer@...belt.com>,
	Alexander Potapenko <glider@...gle.com>,
	kvmarm@...ts.linux.dev,
	Keisuke Nishimura <keisuke.nishimura@...ia.fr>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Atish Patra <atishp@...shpatra.org>,
	Joey Gouly <joey.gouly@....com>,
	x86@...nel.org,
	Marc Zyngier <maz@...nel.org>,
	Sean Christopherson <seanjc@...gle.com>,
	Andre Przywara <andre.przywara@....com>,
	Kunkun Jiang <jiangkunkun@...wei.com>,
	linux-riscv@...ts.infradead.org,
	Randy Dunlap <rdunlap@...radead.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Alexandre Ghiti <alex@...ti.fr>,
	linux-kernel@...r.kernel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	kvm-riscv@...ts.infradead.org,
	Maxim Levitsky <mlevitsk@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Albert Ou <aou@...s.berkeley.edu>
Subject: [PATCH v5 4/6] x86: KVM: SVM: use kvm_lock_all_vcpus instead of a custom implementation

Use kvm_lock_all_vcpus instead of sev's own implementation.

Because kvm_lock_all_vcpus uses the _nest_lock feature of lockdep, which
ignores subclasses, there is no longer a need to use separate subclasses
for source and target VMs.

No functional change intended.

Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/svm/sev.c | 72 +++---------------------------------------
 1 file changed, 4 insertions(+), 68 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 0bc708ee2788..16db6179013d 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1882,70 +1882,6 @@ static void sev_unlock_two_vms(struct kvm *dst_kvm, struct kvm *src_kvm)
 	atomic_set_release(&src_sev->migration_in_progress, 0);
 }
 
-/* vCPU mutex subclasses.  */
-enum sev_migration_role {
-	SEV_MIGRATION_SOURCE = 0,
-	SEV_MIGRATION_TARGET,
-	SEV_NR_MIGRATION_ROLES,
-};
-
-static int sev_lock_vcpus_for_migration(struct kvm *kvm,
-					enum sev_migration_role role)
-{
-	struct kvm_vcpu *vcpu;
-	unsigned long i, j;
-
-	kvm_for_each_vcpu(i, vcpu, kvm) {
-		if (mutex_lock_killable_nested(&vcpu->mutex, role))
-			goto out_unlock;
-
-#ifdef CONFIG_PROVE_LOCKING
-		if (!i)
-			/*
-			 * Reset the role to one that avoids colliding with
-			 * the role used for the first vcpu mutex.
-			 */
-			role = SEV_NR_MIGRATION_ROLES;
-		else
-			mutex_release(&vcpu->mutex.dep_map, _THIS_IP_);
-#endif
-	}
-
-	return 0;
-
-out_unlock:
-
-	kvm_for_each_vcpu(j, vcpu, kvm) {
-		if (i == j)
-			break;
-
-#ifdef CONFIG_PROVE_LOCKING
-		if (j)
-			mutex_acquire(&vcpu->mutex.dep_map, role, 0, _THIS_IP_);
-#endif
-
-		mutex_unlock(&vcpu->mutex);
-	}
-	return -EINTR;
-}
-
-static void sev_unlock_vcpus_for_migration(struct kvm *kvm)
-{
-	struct kvm_vcpu *vcpu;
-	unsigned long i;
-	bool first = true;
-
-	kvm_for_each_vcpu(i, vcpu, kvm) {
-		if (first)
-			first = false;
-		else
-			mutex_acquire(&vcpu->mutex.dep_map,
-				      SEV_NR_MIGRATION_ROLES, 0, _THIS_IP_);
-
-		mutex_unlock(&vcpu->mutex);
-	}
-}
-
 static void sev_migrate_from(struct kvm *dst_kvm, struct kvm *src_kvm)
 {
 	struct kvm_sev_info *dst = to_kvm_sev_info(dst_kvm);
@@ -2083,10 +2019,10 @@ int sev_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd)
 		charged = true;
 	}
 
-	ret = sev_lock_vcpus_for_migration(kvm, SEV_MIGRATION_SOURCE);
+	ret = kvm_lock_all_vcpus(kvm);
 	if (ret)
 		goto out_dst_cgroup;
-	ret = sev_lock_vcpus_for_migration(source_kvm, SEV_MIGRATION_TARGET);
+	ret = kvm_lock_all_vcpus(source_kvm);
 	if (ret)
 		goto out_dst_vcpu;
 
@@ -2100,9 +2036,9 @@ int sev_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd)
 	ret = 0;
 
 out_source_vcpu:
-	sev_unlock_vcpus_for_migration(source_kvm);
+	kvm_unlock_all_vcpus(source_kvm);
 out_dst_vcpu:
-	sev_unlock_vcpus_for_migration(kvm);
+	kvm_unlock_all_vcpus(kvm);
 out_dst_cgroup:
 	/* Operates on the source on success, on the destination on failure.  */
 	if (charged)
-- 
2.46.0