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: cce69af ("RISC-V: KVM: Implement VCPU interrupts and requests handling") Reported-by: Bin Meng <[email protected]> Signed-off-by: Anup Patel <[email protected]> Reviewed-by: Atish Patra <[email protected]> Tested-by: Heinrich Schuchardt <[email protected]> Tested-by: Bin Meng <[email protected]> Signed-off-by: Anup Patel <[email protected]>
fracktal · Jul 11, 2022 · be82abe · be82abe
1 parent 8857338
commit be82abe
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
@@ -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) {
 				/*