This is a note to let you know that I've just added the patch titled RISC-V: KVM: Fix SRCU deadlock caused by kvm_riscv_check_vcpu_requests() to the 5.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: risc-v-kvm-fix-srcu-deadlock-caused-by-kvm_riscv_che.patch and it can be found in the queue-5.18 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 79ed92567dfe00c3d8e228968dc43656176c5131 Author: Anup Patel <apatel@xxxxxxxxxxxxxxxx> Date: Mon Jul 11 09:36:32 2022 +0530 RISC-V: KVM: Fix SRCU deadlock caused by kvm_riscv_check_vcpu_requests() [ Upstream commit be82abe6a76ba8e76f25312566182b0f13c4fbf9 ] 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: cce69aff689e ("RISC-V: KVM: Implement VCPU interrupts and requests handling") Reported-by: Bin Meng <bmeng.cn@xxxxxxxxx> Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx> Reviewed-by: Atish Patra <atishp@xxxxxxxxxxxx> Tested-by: Heinrich Schuchardt <heinrich.schuchardt@xxxxxxxxxxxxx> Tested-by: Bin Meng <bmeng.cn@xxxxxxxxx> Signed-off-by: Anup Patel <anup@xxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c index 7461f964d20a..3894777bfa87 100644 --- a/arch/riscv/kvm/vcpu.c +++ b/arch/riscv/kvm/vcpu.c @@ -673,9 +673,11 @@ 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) { /*