Commit fd92bd3b authored by Maxim Levitsky's avatar Maxim Levitsky Committed by Sean Christopherson
Browse files

KVM: SVM: switch to raw spinlock for svm->ir_list_lock 



Use a raw spinlock for vcpu_svm.ir_list_lock as the lock can be taken
during schedule() via kvm_sched_out() => __avic_vcpu_put(), and "normal"
spinlocks are sleepable locks when PREEMPT_RT=y.

This fixes the following lockdep warning:

  =============================
  [ BUG: Invalid wait context ]
  6.12.0-146.1640_2124176644.el10.x86_64+debug #1 Not tainted
  -----------------------------
  qemu-kvm/38299 is trying to lock:
  ff11000239725600 (&svm->ir_list_lock){....}-{3:3}, at: __avic_vcpu_put+0xfd/0x300 [kvm_amd]
  other info that might help us debug this:
  context-{5:5}
  2 locks held by qemu-kvm/38299:
   #0: ff11000239723ba8 (&vcpu->mutex){+.+.}-{4:4}, at: kvm_vcpu_ioctl+0x240/0xe00 [kvm]
   #1: ff11000b906056d8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2e/0x130
  stack backtrace:
  CPU: 1 UID: 0 PID: 38299 Comm: qemu-kvm Kdump: loaded Not tainted 6.12.0-146.1640_2124176644.el10.x86_64+debug #1 PREEMPT(voluntary)
  Hardware name: AMD Corporation QUARTZ/QUARTZ, BIOS RQZ100AB 09/14/2023
  Call Trace:
   <TASK>
   dump_stack_lvl+0x6f/0xb0
   __lock_acquire+0x921/0xb80
   lock_acquire.part.0+0xbe/0x270
   _raw_spin_lock_irqsave+0x46/0x90
   __avic_vcpu_put+0xfd/0x300 [kvm_amd]
   svm_vcpu_put+0xfa/0x130 [kvm_amd]
   kvm_arch_vcpu_put+0x48c/0x790 [kvm]
   kvm_sched_out+0x161/0x1c0 [kvm]
   prepare_task_switch+0x36b/0xf60
   __schedule+0x4f7/0x1890
   schedule+0xd4/0x260
   xfer_to_guest_mode_handle_work+0x54/0xc0
   vcpu_run+0x69a/0xa70 [kvm]
   kvm_arch_vcpu_ioctl_run+0xdc0/0x17e0 [kvm]
   kvm_vcpu_ioctl+0x39f/0xe00 [kvm]

Signed-off-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
Link: https://patch.msgid.link/20251030194130.307900-1-mlevitsk@redhat.com


[sean: massage changelog]
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent aaac0994

arch/x86/kvm/svm/avic.c

+8 −8
Original line number Diff line number Diff line
@@ -788,7 +788,7 @@ int avic_init_vcpu(struct vcpu_svm *svm) 
	struct kvm_vcpu *vcpu = &svm->vcpu;



	INIT_LIST_HEAD(&svm->ir_list);

	spin_lock_init(&svm->ir_list_lock);

	raw_spin_lock_init(&svm->ir_list_lock);



	if (!enable_apicv || !irqchip_in_kernel(vcpu->kvm))

		return 0;
@@ -816,9 +816,9 @@ static void svm_ir_list_del(struct kvm_kernel_irqfd *irqfd) 
	if (!vcpu)

		return;



	spin_lock_irqsave(&to_svm(vcpu)->ir_list_lock, flags);

	raw_spin_lock_irqsave(&to_svm(vcpu)->ir_list_lock, flags);

	list_del(&irqfd->vcpu_list);

	spin_unlock_irqrestore(&to_svm(vcpu)->ir_list_lock, flags);

	raw_spin_unlock_irqrestore(&to_svm(vcpu)->ir_list_lock, flags);

}



int avic_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
@@ -855,7 +855,7 @@ int avic_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm, 
		 * list of IRQs being posted to the vCPU, to ensure the IRTE

		 * isn't programmed with stale pCPU/IsRunning information.

		 */

		guard(spinlock_irqsave)(&svm->ir_list_lock);

		guard(raw_spinlock_irqsave)(&svm->ir_list_lock);



		/*

		 * Update the target pCPU for IOMMU doorbells if the vCPU is
@@ -972,7 +972,7 @@ static void __avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu, 
	 * up-to-date entry information, or that this task will wait until

	 * svm_ir_list_add() completes to set the new target pCPU.

	 */

	spin_lock_irqsave(&svm->ir_list_lock, flags);

	raw_spin_lock_irqsave(&svm->ir_list_lock, flags);



	entry = svm->avic_physical_id_entry;

	WARN_ON_ONCE(entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK);
@@ -997,7 +997,7 @@ static void __avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu, 


	avic_update_iommu_vcpu_affinity(vcpu, h_physical_id, action);



	spin_unlock_irqrestore(&svm->ir_list_lock, flags);

	raw_spin_unlock_irqrestore(&svm->ir_list_lock, flags);

}



void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
@@ -1035,7 +1035,7 @@ static void __avic_vcpu_put(struct kvm_vcpu *vcpu, enum avic_vcpu_action action) 
	 * or that this task will wait until svm_ir_list_add() completes to

	 * mark the vCPU as not running.

	 */

	spin_lock_irqsave(&svm->ir_list_lock, flags);

	raw_spin_lock_irqsave(&svm->ir_list_lock, flags);



	avic_update_iommu_vcpu_affinity(vcpu, -1, action);
@@ -1059,7 +1059,7 @@ static void __avic_vcpu_put(struct kvm_vcpu *vcpu, enum avic_vcpu_action action) 


	svm->avic_physical_id_entry = entry;



	spin_unlock_irqrestore(&svm->ir_list_lock, flags);

	raw_spin_unlock_irqrestore(&svm->ir_list_lock, flags);

}



void avic_vcpu_put(struct kvm_vcpu *vcpu)

arch/x86/kvm/svm/svm.h

+1 −1
Original line number Diff line number Diff line
@@ -329,7 +329,7 @@ struct vcpu_svm { 
	 * back into remapped mode).

	 */

	struct list_head ir_list;

	spinlock_t ir_list_lock;

	raw_spinlock_t ir_list_lock;



	struct vcpu_sev_es_state sev_es;