| Message ID | CANRm+CwmVnJqCzN1sWhBOKZBCqpL2ZfRbT-V+tHMGFwPjCZGvw@mail.gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [RESEND] KVM: X86: Grab KVM's srcu lock when accessing hv assist page | expand |
On 14/02/20 09:51, Wanpeng Li wrote: > From: Wanpeng Li <wanpengli@tencent.com> > > Acquire kvm->srcu for the duration of mapping eVMCS to fix a bug where accessing > hv assist page derefences ->memslots without holding ->srcu or ->slots_lock. Perhaps nested_sync_vmcs12_to_shadow should be moved to prepare_guest_switch, where the SRCU is already taken. Paolo > It can be reproduced by running KVM's evmcs_test selftest. > > ============================= > WARNING: suspicious RCU usage > 5.6.0-rc1+ #53 Tainted: G W IOE > ----------------------------- > ./include/linux/kvm_host.h:623 suspicious rcu_dereference_check() usage! > > other info that might help us debug this: > > rcu_scheduler_active = 2, debug_locks = 1 > 1 lock held by evmcs_test/8507: > #0: ffff9ddd156d00d0 (&vcpu->mutex){+.+.}, at: > kvm_vcpu_ioctl+0x85/0x680 [kvm] > > stack backtrace: > CPU: 6 PID: 8507 Comm: evmcs_test Tainted: G W IOE 5.6.0-rc1+ #53 > Hardware name: Dell Inc. OptiPlex 7040/0JCTF8, BIOS 1.4.9 09/12/2016 > Call Trace: > dump_stack+0x68/0x9b > kvm_read_guest_cached+0x11d/0x150 [kvm] > kvm_hv_get_assist_page+0x33/0x40 [kvm] > nested_enlightened_vmentry+0x2c/0x60 [kvm_intel] > nested_vmx_handle_enlightened_vmptrld.part.52+0x32/0x1c0 [kvm_intel] > nested_sync_vmcs12_to_shadow+0x439/0x680 [kvm_intel] > vmx_vcpu_run+0x67a/0xe60 [kvm_intel] > vcpu_enter_guest+0x35e/0x1bc0 [kvm] > kvm_arch_vcpu_ioctl_run+0x40b/0x670 [kvm] > kvm_vcpu_ioctl+0x370/0x680 [kvm] > ksys_ioctl+0x235/0x850 > __x64_sys_ioctl+0x16/0x20 > do_syscall_64+0x77/0x780 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > --- > arch/x86/kvm/vmx/nested.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c > index 657c2ed..a68a69d 100644 > --- a/arch/x86/kvm/vmx/nested.c > +++ b/arch/x86/kvm/vmx/nested.c > @@ -1994,14 +1994,18 @@ static int > nested_vmx_handle_enlightened_vmptrld(struct kvm_vcpu *vcpu, > void nested_sync_vmcs12_to_shadow(struct kvm_vcpu *vcpu) > { > struct vcpu_vmx *vmx = to_vmx(vcpu); > + int idx; > > /* > * hv_evmcs may end up being not mapped after migration (when > * L2 was running), map it here to make sure vmcs12 changes are > * properly reflected. > */ > - if (vmx->nested.enlightened_vmcs_enabled && !vmx->nested.hv_evmcs) > + if (vmx->nested.enlightened_vmcs_enabled && !vmx->nested.hv_evmcs) { > + idx = srcu_read_lock(&vcpu->kvm->srcu); > nested_vmx_handle_enlightened_vmptrld(vcpu, false); > + srcu_read_unlock(&vcpu->kvm->srcu, idx); > + } > > if (vmx->nested.hv_evmcs) { > copy_vmcs12_to_enlightened(vmx); > -- > 2.7.4 >
On Fri, 14 Feb 2020 at 16:58, Paolo Bonzini <pbonzini@redhat.com> wrote: > > On 14/02/20 09:51, Wanpeng Li wrote: > > From: Wanpeng Li <wanpengli@tencent.com> > > > > Acquire kvm->srcu for the duration of mapping eVMCS to fix a bug where accessing > > hv assist page derefences ->memslots without holding ->srcu or ->slots_lock. > > Perhaps nested_sync_vmcs12_to_shadow should be moved to > prepare_guest_switch, where the SRCU is already taken. Will do. Wanpeng
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 657c2ed..a68a69d 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -1994,14 +1994,18 @@ static int nested_vmx_handle_enlightened_vmptrld(struct kvm_vcpu *vcpu, void nested_sync_vmcs12_to_shadow(struct kvm_vcpu *vcpu) { struct vcpu_vmx *vmx = to_vmx(vcpu); + int idx; /* * hv_evmcs may end up being not mapped after migration (when * L2 was running), map it here to make sure vmcs12 changes are * properly reflected. */ - if (vmx->nested.enlightened_vmcs_enabled && !vmx->nested.hv_evmcs) + if (vmx->nested.enlightened_vmcs_enabled && !vmx->nested.hv_evmcs) { + idx = srcu_read_lock(&vcpu->kvm->srcu); nested_vmx_handle_enlightened_vmptrld(vcpu, false); + srcu_read_unlock(&vcpu->kvm->srcu, idx); + } if (vmx->nested.hv_evmcs) {