lkml.org 
[lkml]   [2011]   [Jan]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 1/3] KVM: fix rcu usage warning in kvm_arch_vcpu_ioctl_set_sregs()
On Thu, Jan 20, 2011 at 11:03:31AM +0800, Xiao Guangrong wrote:
> On 01/20/2011 02:13 AM, Marcelo Tosatti wrote:
> > On Wed, Jan 19, 2011 at 01:16:23PM +0800, Xiao Guangrong wrote:
> >> On 01/12/2011 03:39 PM, Xiao Guangrong wrote:
> >>> Fix:
> >>>
> >>> [ 1001.499596] ===================================================
> >>> [ 1001.499599] [ INFO: suspicious rcu_dereference_check() usage. ]
> >>> [ 1001.499601] ---------------------------------------------------
> >>> [ 1001.499604] include/linux/kvm_host.h:301 invoked rcu_dereference_check() without protection!
> >>> ......
> >>> [ 1001.499636] Pid: 6035, comm: qemu-system-x86 Not tainted 2.6.37-rc6+ #62
> >>> [ 1001.499638] Call Trace:
> >>> [ 1001.499644] [] lockdep_rcu_dereference+0x9d/0xa5
> >>> [ 1001.499653] [] gfn_to_memslot+0x8d/0xc8 [kvm]
> >>> [ 1001.499661] [] gfn_to_hva+0x16/0x3f [kvm]
> >>> [ 1001.499669] [] kvm_read_guest_page+0x1e/0x5e [kvm]
> >>> [ 1001.499681] [] kvm_read_guest_page_mmu+0x53/0x5e [kvm]
> >>> [ 1001.499699] [] load_pdptrs+0x3f/0x9c [kvm]
> >>> [ 1001.499705] [] ? vmx_set_cr0+0x507/0x517 [kvm_intel]
> >>> [ 1001.499717] [] kvm_arch_vcpu_ioctl_set_sregs+0x1f3/0x3c0 [kvm]
> >>> [ 1001.499727] [] kvm_vcpu_ioctl+0x6a5/0xbc5 [kvm]
> >>>
> >>> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
> >>
> >> Ping ...?
> >
> > Applied this fix. For the make_all_cpus_request optimization, can you
> > show numbers with this new version? Because now there is LOCK# similarly
> > to the spinlock.
>
> Marcelo,
>
> Sure :-), there is the simply test result of kernbench:
>
> Before patch:
>
> real 5m6.493s
> user 3m57.847s
> sys 9m7.115s
>
> real 5m1.750s
> user 4m0.109s
> sys 9m10.192s
>
>
> After patch:
> real 5m0.140s
> user 3m57.956s
> sys 8m58.339s
>
> real 4m56.314s
> user 4m0.303s
> sys 8m55.774s

Nice. One disadvantageous side effect for the kvm_vcpu_kick path
is that it can race with make_all_cpus_request, which is possibly
doing unrelated, slower work (IPI'ing other vcpus, waiting for
response).

Looks ok, but lets wait for more careful reviews before applying.




\
 
 \ /
  Last update: 2011-01-20 16:43    [W:0.107 / U:21.624 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site