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@xxxxxxx>
Reported-by: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>
Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx>
---
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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