Messages in this thread | | | Date | Tue, 11 Nov 2014 13:35:29 +0800 | From | Tang Chen <> | Subject | Re: [PATCH v4] KVM: x86: fix access memslots w/o hold srcu read lock |
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Hi Wanpeng,
I think I have totally missed this thread. I opened lockdep and RCU debug, and tried on 3.18-rc1. But I didn't get the warning. My steps are:
1. Use numactl to bind a qemu process to node1. 2. Offline all node1 memory. And the qemu process is still running.
Would you please tell me how did you reproduce it ?
Thanks.
On 11/02/2014 03:07 PM, Wanpeng Li wrote: > The srcu read lock must be held while accessing memslots (e.g. > when using gfn_to_* functions), however, commit c24ae0dcd3e8 > ("kvm: x86: Unpin and remove kvm_arch->apic_access_page") call > gfn_to_page() in kvm_vcpu_reload_apic_access_page() w/o hold it in > vmx_vcpu_reset() path which leads to suspicious rcu_dereference_check() > usage warning. This patch fix it by holding srcu read lock in all > kvm_vcpu_reset() call path. > > > [ INFO: suspicious RCU usage. ] > 3.18.0-rc2-test2+ #70 Not tainted > ------------------------------- > include/linux/kvm_host.h:474 suspicious rcu_dereference_check() usage! > > other info that might help us debug this: > > rcu_scheduler_active = 1, debug_locks = 0 > 1 lock held by qemu-system-x86/2371: > #0: (&vcpu->mutex){+.+...}, at: [<ffffffffa037d800>] vcpu_load+0x20/0xd0 [kvm] > > stack backtrace: > CPU: 4 PID: 2371 Comm: qemu-system-x86 Not tainted 3.18.0-rc2-test2+ #70 > Hardware name: Dell Inc. OptiPlex 9010/0M9KCM, BIOS A12 01/10/2013 > 0000000000000001 ffff880209983ca8 ffffffff816f514f 0000000000000000 > ffff8802099b8990 ffff880209983cd8 ffffffff810bd687 00000000000fee00 > ffff880208a2c000 ffff880208a10000 ffff88020ef50040 ffff880209983d08 > Call Trace: > [<ffffffff816f514f>] dump_stack+0x4e/0x71 > [<ffffffff810bd687>] lockdep_rcu_suspicious+0xe7/0x120 > [<ffffffffa037d055>] gfn_to_memslot+0xd5/0xe0 [kvm] > [<ffffffffa03807d3>] __gfn_to_pfn+0x33/0x60 [kvm] > [<ffffffffa0380885>] gfn_to_page+0x25/0x90 [kvm] > [<ffffffffa038aeec>] kvm_vcpu_reload_apic_access_page+0x3c/0x80 [kvm] > [<ffffffffa08f0a9c>] vmx_vcpu_reset+0x20c/0x460 [kvm_intel] > [<ffffffffa039ab8e>] kvm_vcpu_reset+0x15e/0x1b0 [kvm] > [<ffffffffa039ac0c>] kvm_arch_vcpu_setup+0x2c/0x50 [kvm] > [<ffffffffa037f7e0>] kvm_vm_ioctl+0x1d0/0x780 [kvm] > [<ffffffff810bc664>] ? __lock_is_held+0x54/0x80 > [<ffffffff812231f0>] do_vfs_ioctl+0x300/0x520 > [<ffffffff8122ee45>] ? __fget+0x5/0x250 > [<ffffffff8122f0fa>] ? __fget_light+0x2a/0xe0 > [<ffffffff81223491>] SyS_ioctl+0x81/0xa0 > [<ffffffff816fed6d>] system_call_fastpath+0x16/0x1b > > Reported-by: Takashi Iwai <tiwai@suse.de> > Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com> > Suggested-by: Paolo Bonzini <pbonzini@redhat.com> > Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com> > --- > v3 -> v4: > * bypass the problem altoghter by kvm_make_request > v2 -> v3: > * take care all vmx_vcpu_reset call path > v1 -> v2: > * just fix hold the srcu read lock in vmx_vcpu_reset path > > arch/x86/kvm/vmx.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index a0f78db..3e556c6 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -4579,7 +4579,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu) > vmcs_write32(TPR_THRESHOLD, 0); > } > > - kvm_vcpu_reload_apic_access_page(vcpu); > + kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu); > > if (vmx_vm_has_apicv(vcpu->kvm)) > memset(&vmx->pi_desc, 0, sizeof(struct pi_desc));
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