From: Anup Patel <apatel@ventanamicro.com>
To: Paolo Bonzini <pbonzini@redhat.com>, Atish Patra <atishp@atishpatra.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Alistair Francis <Alistair.Francis@wdc.com>,
Bin Meng <bmeng.cn@gmail.com>,
Heinrich Schuchardt <heinrich.schuchardt@canonical.com>,
Anup Patel <anup@brainfault.org>,
kvm@vger.kernel.org, kvm-riscv@lists.infradead.org,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
Anup Patel <apatel@ventanamicro.com>
Subject: [PATCH] RISC-V: KVM: Fix SRCU deadlock caused by kvm_riscv_check_vcpu_requests()
Date: Sun, 10 Jul 2022 20:41:05 +0530 [thread overview]
Message-ID: <20220710151105.687193-1-apatel@ventanamicro.com> (raw)
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>
---
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 b7a433c54d0f..5d271b597613 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -845,9 +845,11 @@ 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) {
/*
--
2.34.1
next reply other threads:[~2022-07-10 15:11 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-10 15:11 Anup Patel [this message]
2022-07-10 19:05 ` [PATCH] RISC-V: KVM: Fix SRCU deadlock caused by kvm_riscv_check_vcpu_requests() Atish Patra
2022-07-10 19:05 ` Heinrich Schuchardt
2022-07-11 1:37 ` Bin Meng
2022-07-11 4:16 ` Anup Patel
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