From: Alexey Kardashevskiy aik@ozlabs.ru
[ Upstream commit 345077c8e172c255ea0707214303ccd099e5656b ]
Guest physical to user address translation uses KVM memslots and reading these requires holding the kvm->srcu lock. However recently introduced kvmppc_tce_validate() broke the rule (see the lockdep warning below).
This moves srcu_read_lock(&vcpu->kvm->srcu) earlier to protect kvmppc_tce_validate() as well.
============================= WARNING: suspicious RCU usage 5.1.0-rc2-le_nv2_aikATfstn1-p1 #380 Not tainted ----------------------------- include/linux/kvm_host.h:605 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1 1 lock held by qemu-system-ppc/8020: #0: 0000000094972fe9 (&vcpu->mutex){+.+.}, at: kvm_vcpu_ioctl+0xdc/0x850 [kvm]
stack backtrace: CPU: 44 PID: 8020 Comm: qemu-system-ppc Not tainted 5.1.0-rc2-le_nv2_aikATfstn1-p1 #380 Call Trace: [c000003fece8f740] [c000000000bcc134] dump_stack+0xe8/0x164 (unreliable) [c000003fece8f790] [c000000000181be0] lockdep_rcu_suspicious+0x130/0x170 [c000003fece8f810] [c0000000000d5f50] kvmppc_tce_to_ua+0x280/0x290 [c000003fece8f870] [c00800001a7e2c78] kvmppc_tce_validate+0x80/0x1b0 [kvm] [c000003fece8f8e0] [c00800001a7e3fac] kvmppc_h_put_tce+0x94/0x3e4 [kvm] [c000003fece8f9a0] [c00800001a8baac4] kvmppc_pseries_do_hcall+0x30c/0xce0 [kvm_hv] [c000003fece8fa10] [c00800001a8bd89c] kvmppc_vcpu_run_hv+0x694/0xec0 [kvm_hv] [c000003fece8fae0] [c00800001a7d95dc] kvmppc_vcpu_run+0x34/0x48 [kvm] [c000003fece8fb00] [c00800001a7d56bc] kvm_arch_vcpu_ioctl_run+0x2f4/0x400 [kvm] [c000003fece8fb90] [c00800001a7c3618] kvm_vcpu_ioctl+0x460/0x850 [kvm] [c000003fece8fd00] [c00000000041c4f4] do_vfs_ioctl+0xe4/0x930 [c000003fece8fdb0] [c00000000041ce04] ksys_ioctl+0xc4/0x110 [c000003fece8fe00] [c00000000041ce78] sys_ioctl+0x28/0x80 [c000003fece8fe20] [c00000000000b5a4] system_call+0x5c/0x70
Fixes: 42de7b9e2167 ("KVM: PPC: Validate TCEs against preregistered memory page sizes", 2018-09-10) Signed-off-by: Alexey Kardashevskiy aik@ozlabs.ru Signed-off-by: Paul Mackerras paulus@ozlabs.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/kvm/book3s_64_vio.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c index 532ab79734c7a..d43e8fe6d4241 100644 --- a/arch/powerpc/kvm/book3s_64_vio.c +++ b/arch/powerpc/kvm/book3s_64_vio.c @@ -543,14 +543,14 @@ long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn, if (ret != H_SUCCESS) return ret;
+ idx = srcu_read_lock(&vcpu->kvm->srcu); + ret = kvmppc_tce_validate(stt, tce); if (ret != H_SUCCESS) - return ret; + goto unlock_exit;
dir = iommu_tce_direction(tce);
- idx = srcu_read_lock(&vcpu->kvm->srcu); - if ((dir != DMA_NONE) && kvmppc_tce_to_ua(vcpu->kvm, tce, &ua, NULL)) { ret = H_PARAMETER; goto unlock_exit;