* kvm_set_shared_msr using smp_processor_id() in preemptible code
@ 2012-04-18 2:58 Dave Jones
2012-04-18 12:03 ` [PATCH 3.4-rc] KVM: VMX: Fix kvm_set_shared_msr() called in preemptible context Avi Kivity
0 siblings, 1 reply; 3+ messages in thread
From: Dave Jones @ 2012-04-18 2:58 UTC (permalink / raw)
To: Linux Kernel; +Cc: avi
I see a bunch of these when I start a kvm guest using Linus' current tree.
Dave
BUG: using smp_processor_id() in preemptible [00000000] code: qemu-kvm/22713
caller is kvm_set_shared_msr+0x32/0xa0 [kvm]
Pid: 22713, comm: qemu-kvm Not tainted 3.4.0-rc3+ #39
Call Trace:
[<ffffffff8131fa82>] debug_smp_processor_id+0xe2/0x100
[<ffffffffa0328ae2>] kvm_set_shared_msr+0x32/0xa0 [kvm]
[<ffffffffa03a103b>] vmx_set_msr+0x28b/0x2d0 [kvm_intel]
[<ffffffffa03a5f1a>] handle_wrmsr+0x4a/0x310 [kvm_intel]
[<ffffffffa03a7638>] vmx_handle_exit+0xc8/0x6f0 [kvm_intel]
[<ffffffffa03354f6>] kvm_arch_vcpu_ioctl_run+0x616/0x18c0 [kvm]
[<ffffffffa0335445>] ? kvm_arch_vcpu_ioctl_run+0x565/0x18c0 [kvm]
[<ffffffff8164dc47>] ? mutex_lock_nested+0x2c7/0x3c0
[<ffffffffa031b5ca>] ? vcpu_load+0x1a/0xb0 [kvm]
[<ffffffffa031bb35>] kvm_vcpu_ioctl+0x465/0x780 [kvm]
[<ffffffff81078ef9>] ? creds_are_invalid+0x29/0x60
[<ffffffff812aec85>] ? inode_has_perm+0x35/0xa0
[<ffffffff811ba5e8>] do_vfs_ioctl+0x98/0x570
[<ffffffff811bab51>] sys_ioctl+0x91/0xa0
[<ffffffff81659692>] system_call_fastpath+0x16/0x1b
BUG: using smp_processor_id() in preemptible [00000000] code: qemu-kvm/22713
caller is user_return_notifier_register+0x2f/0x70
Pid: 22713, comm: qemu-kvm Not tainted 3.4.0-rc3+ #39
Call Trace:
[<ffffffff8131fa82>] debug_smp_processor_id+0xe2/0x100
[<ffffffff81134eaf>] user_return_notifier_register+0x2f/0x70
[<ffffffffa0328b47>] kvm_set_shared_msr+0x97/0xa0 [kvm]
[<ffffffffa03a103b>] vmx_set_msr+0x28b/0x2d0 [kvm_intel]
[<ffffffffa03248e0>] ? kvm_enable_efer_bits+0x20/0x20 [kvm]
[<ffffffffa03248f9>] do_set_msr+0x19/0x20 [kvm]
[<ffffffffa032be51>] msr_io+0x101/0x220 [kvm]
[<ffffffffa032bdcf>] ? msr_io+0x7f/0x220 [kvm]
[<ffffffffa03307fa>] kvm_arch_vcpu_ioctl+0x30a/0x1030 [kvm]
[<ffffffffa031b5ca>] ? vcpu_load+0x1a/0xb0 [kvm]
[<ffffffffa03a1f45>] ? vmx_vcpu_load+0x35/0x1b0 [kvm_intel]
[<ffffffff81083fe1>] ? get_parent_ip+0x11/0x50
[<ffffffff8165570d>] ? sub_preempt_count+0x9d/0xd0
[<ffffffffa031b77e>] kvm_vcpu_ioctl+0xae/0x780 [kvm]
[<ffffffff81078ef9>] ? creds_are_invalid+0x29/0x60
[<ffffffff812aec85>] ? inode_has_perm+0x35/0xa0
[<ffffffff811ba5e8>] do_vfs_ioctl+0x98/0x570
[<ffffffff811bab51>] sys_ioctl+0x91/0xa0
[<ffffffff81659692>] system_call_fastpath+0x16/0x1b
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH 3.4-rc] KVM: VMX: Fix kvm_set_shared_msr() called in preemptible context
2012-04-18 2:58 kvm_set_shared_msr using smp_processor_id() in preemptible code Dave Jones
@ 2012-04-18 12:03 ` Avi Kivity
2012-04-19 2:42 ` Marcelo Tosatti
0 siblings, 1 reply; 3+ messages in thread
From: Avi Kivity @ 2012-04-18 12:03 UTC (permalink / raw)
To: kvm, Marcelo Tosatti; +Cc: linux-kernel, davej
kvm_set_shared_msr() may not be called in preemptible context,
but vmx_set_msr() does so:
BUG: using smp_processor_id() in preemptible [00000000] code: qemu-kvm/22713
caller is kvm_set_shared_msr+0x32/0xa0 [kvm]
Pid: 22713, comm: qemu-kvm Not tainted 3.4.0-rc3+ #39
Call Trace:
[<ffffffff8131fa82>] debug_smp_processor_id+0xe2/0x100
[<ffffffffa0328ae2>] kvm_set_shared_msr+0x32/0xa0 [kvm]
[<ffffffffa03a103b>] vmx_set_msr+0x28b/0x2d0 [kvm_intel]
...
Making kvm_set_shared_msr() work in preemptible is cleaner, but
it's used in the fast path. Making two variants is overkill, so
this patch just disables preemption around the call.
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
arch/x86/kvm/vmx.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index ad85adf..4ff0ab9 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2210,9 +2210,12 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
msr = find_msr_entry(vmx, msr_index);
if (msr) {
msr->data = data;
- if (msr - vmx->guest_msrs < vmx->save_nmsrs)
+ if (msr - vmx->guest_msrs < vmx->save_nmsrs) {
+ preempt_disable();
kvm_set_shared_msr(msr->index, msr->data,
msr->mask);
+ preempt_enable();
+ }
break;
}
ret = kvm_set_msr_common(vcpu, msr_index, data);
--
1.7.10
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH 3.4-rc] KVM: VMX: Fix kvm_set_shared_msr() called in preemptible context
2012-04-18 12:03 ` [PATCH 3.4-rc] KVM: VMX: Fix kvm_set_shared_msr() called in preemptible context Avi Kivity
@ 2012-04-19 2:42 ` Marcelo Tosatti
0 siblings, 0 replies; 3+ messages in thread
From: Marcelo Tosatti @ 2012-04-19 2:42 UTC (permalink / raw)
To: Avi Kivity; +Cc: kvm, linux-kernel, davej
On Wed, Apr 18, 2012 at 03:03:04PM +0300, Avi Kivity wrote:
> kvm_set_shared_msr() may not be called in preemptible context,
> but vmx_set_msr() does so:
>
> BUG: using smp_processor_id() in preemptible [00000000] code: qemu-kvm/22713
> caller is kvm_set_shared_msr+0x32/0xa0 [kvm]
> Pid: 22713, comm: qemu-kvm Not tainted 3.4.0-rc3+ #39
> Call Trace:
> [<ffffffff8131fa82>] debug_smp_processor_id+0xe2/0x100
> [<ffffffffa0328ae2>] kvm_set_shared_msr+0x32/0xa0 [kvm]
> [<ffffffffa03a103b>] vmx_set_msr+0x28b/0x2d0 [kvm_intel]
> ...
>
> Making kvm_set_shared_msr() work in preemptible is cleaner, but
> it's used in the fast path. Making two variants is overkill, so
> this patch just disables preemption around the call.
>
> Reported-by: Dave Jones <davej@redhat.com>
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
> arch/x86/kvm/vmx.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
Applied, thanks.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2012-04-19 2:48 UTC | newest]
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2012-04-18 2:58 kvm_set_shared_msr using smp_processor_id() in preemptible code Dave Jones
2012-04-18 12:03 ` [PATCH 3.4-rc] KVM: VMX: Fix kvm_set_shared_msr() called in preemptible context Avi Kivity
2012-04-19 2:42 ` Marcelo Tosatti
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