Commit be82abe6 authored by Anup Patel's avatar Anup Patel Committed by Anup Patel
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RISC-V: KVM: Fix SRCU deadlock caused by kvm_riscv_check_vcpu_requests() 



The kvm_riscv_check_vcpu_requests() is called with SRCU read lock held
and for KVM_REQ_SLEEP request it will block the VCPU without releasing
SRCU read lock. This causes KVM ioctls (such as KVM_IOEVENTFD) from
other VCPUs of the same Guest/VM to hang/deadlock if there is any
synchronize_srcu() or synchronize_srcu_expedited() in the path.

To fix the above in kvm_riscv_check_vcpu_requests(), we should do SRCU
read unlock before blocking the VCPU and do SRCU read lock after VCPU
wakeup.

Fixes: cce69aff ("RISC-V: KVM: Implement VCPU interrupts and requests handling")
Reported-by: default avatarBin Meng <bmeng.cn@gmail.com>
Signed-off-by: default avatarAnup Patel <apatel@ventanamicro.com>
Reviewed-by: default avatarAtish Patra <atishp@rivosinc.com>
Tested-by: default avatarHeinrich Schuchardt <heinrich.schuchardt@canonical.com>
Tested-by: default avatarBin Meng <bmeng.cn@gmail.com>
Signed-off-by: default avatarAnup Patel <anup@brainfault.org>
parent 88573389

arch/riscv/kvm/vcpu.c

+2 −0
Original line number Diff line number Diff line
@@ -781,9 +781,11 @@ static void kvm_riscv_check_vcpu_requests(struct kvm_vcpu *vcpu) 


	if (kvm_request_pending(vcpu)) {

		if (kvm_check_request(KVM_REQ_SLEEP, vcpu)) {

			kvm_vcpu_srcu_read_unlock(vcpu);

			rcuwait_wait_event(wait,

				(!vcpu->arch.power_off) && (!vcpu->arch.pause),

				TASK_INTERRUPTIBLE);

			kvm_vcpu_srcu_read_lock(vcpu);



			if (vcpu->arch.power_off || vcpu->arch.pause) {

				/*