2010-06-08 02:19:21

by Xiao Guangrong

Subject: [PATCH] KVM: VMX: fix rcu usage warning

fix:

[ INFO: suspicious rcu_dereference_check() usage. ]
---------------------------------------------------
include/linux/kvm_host.h:258 invoked rcu_dereference_check() without protection!

other info that might help us debug this:


rcu_scheduler_active = 1, debug_locks = 1
1 lock held by qemu-system-x86/3796:
#0: (&vcpu->mutex){+.+.+.}, at: [<ffffffffa0217fd8>] vcpu_load+0x1a/0x66 [kvm]

stack backtrace:
Pid: 3796, comm: qemu-system-x86 Not tainted 2.6.34 #25
Call Trace:
[<ffffffff81070ed1>] lockdep_rcu_dereference+0x9d/0xa5
[<ffffffffa0214fdf>] gfn_to_memslot_unaliased+0x65/0xa0 [kvm]
[<ffffffffa0216139>] gfn_to_hva+0x22/0x4c [kvm]
[<ffffffffa0216217>] kvm_write_guest_page+0x2a/0x7f [kvm]
[<ffffffffa0216286>] kvm_clear_guest_page+0x1a/0x1c [kvm]
[<ffffffffa0278239>] init_rmode+0x3b/0x180 [kvm_intel]
[<ffffffffa02786ce>] vmx_set_cr0+0x350/0x4d3 [kvm_intel]
[<ffffffffa02274ff>] kvm_arch_vcpu_ioctl_set_sregs+0x122/0x31a [kvm]
[<ffffffffa021859c>] kvm_vcpu_ioctl+0x578/0xa3d [kvm]
[<ffffffff8106624c>] ? cpu_clock+0x2d/0x40
[<ffffffff810f7d86>] ? fget_light+0x244/0x28e
[<ffffffff810709b9>] ? trace_hardirqs_off_caller+0x1f/0x10e
[<ffffffff8110501b>] vfs_ioctl+0x32/0xa6
[<ffffffff81105597>] do_vfs_ioctl+0x47f/0x4b8
[<ffffffff813ae654>] ? sub_preempt_count+0xa3/0xb7
[<ffffffff810f7da8>] ? fget_light+0x266/0x28e
[<ffffffff810f7c53>] ? fget_light+0x111/0x28e
[<ffffffff81105617>] sys_ioctl+0x47/0x6a
[<ffffffff81002c1b>] system_call_fastpath+0x16/0x1b

Signed-off-by: Xiao Guangrong <[email protected]>
---
arch/x86/kvm/vmx.c | 17 +++++++++++------
1 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index fdb18cf..ad8a38e 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2643,21 +2643,27 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)

static int init_rmode(struct kvm *kvm)
{
+ int idx, ret = 0;
+
+ idx = srcu_read_lock(&kvm->srcu);
if (!init_rmode_tss(kvm))
- return 0;
+ goto exit;
if (!init_rmode_identity_map(kvm))
- return 0;
- return 1;
+ goto exit;
+
+ ret = 1;
+exit:
+ srcu_read_unlock(&kvm->srcu, idx);
+ return ret;
}

static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
u64 msr;
- int ret, idx;
+ int ret;

vcpu->arch.regs_avail = ~((1 << VCPU_REGS_RIP) | (1 << VCPU_REGS_RSP));
- idx = srcu_read_lock(&vcpu->kvm->srcu);
if (!init_rmode(vmx->vcpu.kvm)) {
ret = -ENOMEM;
goto out;
@@ -2767,7 +2773,6 @@ static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
vmx->emulation_required = 0;

out:
- srcu_read_unlock(&vcpu->kvm->srcu, idx);
return ret;
}

--
1.6.1.2

2010-06-08 08:11:21

by Avi Kivity

Subject: Re: [PATCH] KVM: VMX: fix rcu usage warning

On 06/08/2010 05:15 AM, Xiao Guangrong wrote:
> fix:
>
> [ INFO: suspicious rcu_dereference_check() usage. ]
> ---------------------------------------------------
> include/linux/kvm_host.h:258 invoked rcu_dereference_check() without protection!
>
> other info that might help us debug this:
>
>
> rcu_scheduler_active = 1, debug_locks = 1
> 1 lock held by qemu-system-x86/3796:
> #0: (&vcpu->mutex){+.+.+.}, at: [<ffffffffa0217fd8>] vcpu_load+0x1a/0x66 [kvm]
>
> stack backtrace:
> Pid: 3796, comm: qemu-system-x86 Not tainted 2.6.34 #25
> Call Trace:
> [<ffffffff81070ed1>] lockdep_rcu_dereference+0x9d/0xa5
> [<ffffffffa0214fdf>] gfn_to_memslot_unaliased+0x65/0xa0 [kvm]
> [<ffffffffa0216139>] gfn_to_hva+0x22/0x4c [kvm]
> [<ffffffffa0216217>] kvm_write_guest_page+0x2a/0x7f [kvm]
> [<ffffffffa0216286>] kvm_clear_guest_page+0x1a/0x1c [kvm]
> [<ffffffffa0278239>] init_rmode+0x3b/0x180 [kvm_intel]
> [<ffffffffa02786ce>] vmx_set_cr0+0x350/0x4d3 [kvm_intel]
> [<ffffffffa02274ff>] kvm_arch_vcpu_ioctl_set_sregs+0x122/0x31a [kvm]
> [<ffffffffa021859c>] kvm_vcpu_ioctl+0x578/0xa3d [kvm]
> [<ffffffff8106624c>] ? cpu_clock+0x2d/0x40
> [<ffffffff810f7d86>] ? fget_light+0x244/0x28e
> [<ffffffff810709b9>] ? trace_hardirqs_off_caller+0x1f/0x10e
> [<ffffffff8110501b>] vfs_ioctl+0x32/0xa6
> [<ffffffff81105597>] do_vfs_ioctl+0x47f/0x4b8
> [<ffffffff813ae654>] ? sub_preempt_count+0xa3/0xb7
> [<ffffffff810f7da8>] ? fget_light+0x266/0x28e
> [<ffffffff810f7c53>] ? fget_light+0x111/0x28e
> [<ffffffff81105617>] sys_ioctl+0x47/0x6a
> [<ffffffff81002c1b>] system_call_fastpath+0x16/0x1b
>
>

Applied, thanks.

--
error compiling committee.c: too many arguments to function