| From | Greg Kroah-Hartman <> | Subject | [PATCH 5.18 089/231] RISC-V: KVM: Fix SRCU deadlock caused by kvm_riscv_check_vcpu_requests() | Date | Tue, 19 Jul 2022 13:52:54 +0200 |
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From: Anup Patel <apatel@ventanamicro.com>
[ 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@gmail.com> Signed-off-by: Anup Patel <apatel@ventanamicro.com> Reviewed-by: Atish Patra <atishp@rivosinc.com> Tested-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com> Tested-by: Bin Meng <bmeng.cn@gmail.com> Signed-off-by: Anup Patel <anup@brainfault.org> Signed-off-by: Sasha Levin <sashal@kernel.org> --- arch/riscv/kvm/vcpu.c | 2 ++ 1 file changed, 2 insertions(+)
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) { /* -- 2.35.1
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