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From: Sean Christopherson <seanjc@google.com>
To: Madhavan Srinivasan <maddy@linux.ibm.com>,
	Anup Patel <anup@brainfault.org>,  Paul Walmsley <pjw@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	 Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	 Kiryl Shutsemau <kas@kernel.org>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: "Nicholas Piggin" <npiggin@gmail.com>,
	"Atish Patra" <atish.patra@linux.dev>,
	"Alexandre Ghiti" <alex@ghiti.fr>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org,
	kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org,
	x86@kernel.org, linux-coco@lists.linux.dev,
	linux-kernel@vger.kernel.org,
	"Jean-Christophe Guillain" <jean-christophe@guillain.net>,
	"Paweł S" <spawel523@gmail.com>
Subject: [PATCH v2 7/7] KVM: WARN if vCPU creation is in-progress when locking all vCPUs
Date: Mon, 21 Sep 2026 10:44:45 -0700	[thread overview]
Message-ID: <20260921174445.911676-8-seanjc@google.com> (raw)
In-Reply-To: <20260921174445.911676-1-seanjc@google.com>

Now that KVM holds kvm->lock for the entirety of vCPU creation, from when
created_vcpus is incremented until the new vCPU is fully onlined, WARN if
the impossible happens and KVM somehow sees a discrepancy between the
number of vCPUs "created" and "onlined".

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 virt/kvm/kvm_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 985af39b980a..e66d9761ee49 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1363,7 +1363,7 @@ int kvm_trylock_all_vcpus(struct kvm *kvm)
 
 	lockdep_assert_held(&kvm->lock);
 
-	if (kvm_is_vcpu_creation_in_progress(kvm))
+	if (WARN_ON_ONCE(kvm_is_vcpu_creation_in_progress(kvm)))
 		return -EBUSY;
 
 	kvm_for_each_vcpu(i, vcpu, kvm)
@@ -1389,7 +1389,7 @@ int kvm_lock_all_vcpus(struct kvm *kvm)
 
 	lockdep_assert_held(&kvm->lock);
 
-	if (kvm_is_vcpu_creation_in_progress(kvm))
+	if (WARN_ON_ONCE(kvm_is_vcpu_creation_in_progress(kvm)))
 		return -EBUSY;
 
 	kvm_for_each_vcpu(i, vcpu, kvm) {
-- 
2.55.0.1082.g2b9226bbc0-goog


-- 
kvm-riscv mailing list
kvm-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kvm-riscv

WARNING: multiple messages have this Message-ID (diff)
From: Sean Christopherson <seanjc@google.com>
To: Madhavan Srinivasan <maddy@linux.ibm.com>,
	Anup Patel <anup@brainfault.org>,  Paul Walmsley <pjw@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	 Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	 Kiryl Shutsemau <kas@kernel.org>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: "Nicholas Piggin" <npiggin@gmail.com>,
	"Atish Patra" <atish.patra@linux.dev>,
	"Alexandre Ghiti" <alex@ghiti.fr>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org,
	kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org,
	x86@kernel.org, linux-coco@lists.linux.dev,
	linux-kernel@vger.kernel.org,
	"Jean-Christophe Guillain" <jean-christophe@guillain.net>,
	"Paweł S" <spawel523@gmail.com>
Subject: [PATCH v2 7/7] KVM: WARN if vCPU creation is in-progress when locking all vCPUs
Date: Mon, 21 Sep 2026 10:44:45 -0700	[thread overview]
Message-ID: <20260921174445.911676-8-seanjc@google.com> (raw)
In-Reply-To: <20260921174445.911676-1-seanjc@google.com>

Now that KVM holds kvm->lock for the entirety of vCPU creation, from when
created_vcpus is incremented until the new vCPU is fully onlined, WARN if
the impossible happens and KVM somehow sees a discrepancy between the
number of vCPUs "created" and "onlined".

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 virt/kvm/kvm_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 985af39b980a..e66d9761ee49 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1363,7 +1363,7 @@ int kvm_trylock_all_vcpus(struct kvm *kvm)
 
 	lockdep_assert_held(&kvm->lock);
 
-	if (kvm_is_vcpu_creation_in_progress(kvm))
+	if (WARN_ON_ONCE(kvm_is_vcpu_creation_in_progress(kvm)))
 		return -EBUSY;
 
 	kvm_for_each_vcpu(i, vcpu, kvm)
@@ -1389,7 +1389,7 @@ int kvm_lock_all_vcpus(struct kvm *kvm)
 
 	lockdep_assert_held(&kvm->lock);
 
-	if (kvm_is_vcpu_creation_in_progress(kvm))
+	if (WARN_ON_ONCE(kvm_is_vcpu_creation_in_progress(kvm)))
 		return -EBUSY;
 
 	kvm_for_each_vcpu(i, vcpu, kvm) {
-- 
2.55.0.1082.g2b9226bbc0-goog


WARNING: multiple messages have this Message-ID (diff)
From: Sean Christopherson <seanjc@google.com>
To: Madhavan Srinivasan <maddy@linux.ibm.com>,
	Anup Patel <anup@brainfault.org>,  Paul Walmsley <pjw@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	 Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	 Kiryl Shutsemau <kas@kernel.org>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: "Nicholas Piggin" <npiggin@gmail.com>,
	"Atish Patra" <atish.patra@linux.dev>,
	"Alexandre Ghiti" <alex@ghiti.fr>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org,
	kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org,
	x86@kernel.org, linux-coco@lists.linux.dev,
	linux-kernel@vger.kernel.org,
	"Jean-Christophe Guillain" <jean-christophe@guillain.net>,
	"Paweł S" <spawel523@gmail.com>
Subject: [PATCH v2 7/7] KVM: WARN if vCPU creation is in-progress when locking all vCPUs
Date: Mon, 21 Sep 2026 10:44:45 -0700	[thread overview]
Message-ID: <20260921174445.911676-8-seanjc@google.com> (raw)
In-Reply-To: <20260921174445.911676-1-seanjc@google.com>

Now that KVM holds kvm->lock for the entirety of vCPU creation, from when
created_vcpus is incremented until the new vCPU is fully onlined, WARN if
the impossible happens and KVM somehow sees a discrepancy between the
number of vCPUs "created" and "onlined".

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 virt/kvm/kvm_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 985af39b980a..e66d9761ee49 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1363,7 +1363,7 @@ int kvm_trylock_all_vcpus(struct kvm *kvm)
 
 	lockdep_assert_held(&kvm->lock);
 
-	if (kvm_is_vcpu_creation_in_progress(kvm))
+	if (WARN_ON_ONCE(kvm_is_vcpu_creation_in_progress(kvm)))
 		return -EBUSY;
 
 	kvm_for_each_vcpu(i, vcpu, kvm)
@@ -1389,7 +1389,7 @@ int kvm_lock_all_vcpus(struct kvm *kvm)
 
 	lockdep_assert_held(&kvm->lock);
 
-	if (kvm_is_vcpu_creation_in_progress(kvm))
+	if (WARN_ON_ONCE(kvm_is_vcpu_creation_in_progress(kvm)))
 		return -EBUSY;
 
 	kvm_for_each_vcpu(i, vcpu, kvm) {
-- 
2.55.0.1082.g2b9226bbc0-goog


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

  parent reply	other threads:[~2026-09-21 17:45 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-21 17:44 [PATCH v2 0/7] KVM: Serialize vCPU creation and revert vcpu_ids tracking Sean Christopherson
2026-09-21 17:44 ` Sean Christopherson
2026-09-21 17:44 ` Sean Christopherson
2026-09-21 17:44 ` [PATCH v2 1/7] KVM: Reject attempts to lock all vCPUs if vCPU creation is in-progress Sean Christopherson
2026-09-21 17:44   ` Sean Christopherson
2026-09-21 17:44   ` Sean Christopherson
2026-09-21 17:44 ` [PATCH v2 2/7] KVM: arm64: vgic: Rely on vCPU creation check in "trylock all vCPUs" Sean Christopherson
2026-09-21 17:44   ` Sean Christopherson
2026-09-21 17:44   ` Sean Christopherson
2026-09-21 17:44 ` [PATCH v2 3/7] KVM: RISC-V: Use kvm_is_vcpu_creation_in_progress() instead of open-coded equivalent Sean Christopherson
2026-09-21 17:44   ` Sean Christopherson
2026-09-21 17:44   ` Sean Christopherson
2026-09-21 17:44 ` [PATCH v2 4/7] KVM: Protect all of kvm_vm_ioctl_create_vcpu() with kvm->lock Sean Christopherson
2026-09-21 17:44   ` Sean Christopherson
2026-09-21 17:44   ` Sean Christopherson
2026-09-21 17:59   ` sashiko-bot
2026-09-21 17:44 ` [PATCH v2 5/7] KVM: Move check for existing vCPU ID to the top of vCPU creation Sean Christopherson
2026-09-21 17:44   ` Sean Christopherson
2026-09-21 17:44   ` Sean Christopherson
2026-09-21 17:44 ` [PATCH v2 6/7] Revert "KVM: Check for duplicate vcpu_id as early as possible" Sean Christopherson
2026-09-21 17:44   ` Sean Christopherson
2026-09-21 17:44   ` Sean Christopherson
2026-09-21 17:44 ` Sean Christopherson [this message]
2026-09-21 17:44   ` [PATCH v2 7/7] KVM: WARN if vCPU creation is in-progress when locking all vCPUs Sean Christopherson
2026-09-21 17:44   ` Sean Christopherson
2026-09-22  8:06 ` [PATCH v2 0/7] KVM: Serialize vCPU creation and revert vcpu_ids tracking Jean-Christophe Guillain
2026-09-22  8:06   ` Jean-Christophe Guillain
2026-09-22  8:06   ` Jean-Christophe Guillain
2026-09-22 19:15 ` Naveen N Rao
2026-09-22 19:15   ` Naveen N Rao
2026-09-22 19:15   ` Naveen N Rao
2026-09-26  5:18 ` Paolo Bonzini
2026-09-26  5:18   ` Paolo Bonzini
2026-09-26  5:18   ` Paolo Bonzini

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