Re: [PATCH] KVM: PPC: Take the kvm->srcu lock in kvmppc_h_logical_ci_load/store()

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On Mon, Sep 21, 2015 at 07:50:22AM +0200, Paolo Bonzini wrote:
> 
> 
> On 21/09/2015 03:37, David Gibson wrote:
> > On Fri, Sep 18, 2015 at 08:57:28AM +0200, Thomas Huth wrote:
> >> Access to the kvm->buses (like with the kvm_io_bus_read() and
> >> -write() functions) has to be protected via the kvm->srcu lock. 
> >> The kvmppc_h_logical_ci_load() and -store() functions are
> >> missing this lock so far, so let's add it there, too. This fixes
> >> the problem that the kernel reports "suspicious RCU usage" when
> >> lock debugging is enabled.
> >> 
> >> Fixes: 99342cf8044420eebdf9297ca03a14cb6a7085a1 Signed-off-by:
> >> Thomas Huth <thuth@xxxxxxxxxx>
> > 
> > Nice catch.  Looks like I missed this because the places 
> > kvm_io_bus_{read,write}() are called on x86 are buried about 5
> > layers below where the srcu lock is taken :/.
> > 
> > Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
...
> Paul,
> 
> shall I take this directly into my tree for -rc3?
> 
> Paolo

I have that and two other fixes in my kvm-ppc-fixes branch on
kernel.org.  They were in linux-next today.  I was going to send you a
pull request tomorrow, but if you are about to send stuff off to Linus
you could pull now from:

git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc.git kvm-ppc-fixes

The three patches in there are:

Gautham R. Shenoy (1):
      KVM: PPC: Book3S HV: Pass the correct trap argument to kvmhv_commence_exit

Paul Mackerras (1):
      KVM: PPC: Book3S HV: Fix handling of interrupted VCPUs

Thomas Huth (1):
      KVM: PPC: Book3S: Take the kvm->srcu lock in kvmppc_h_logical_ci_load/store()

The one from Gautham is a 1-liner that has been around for months and
got missed, and is obviously correct.  The one from me fixes a
regression that was introduced in 4.3-rc1 by one of my patches, which
causes oopses and soft lockups due to a use-after-free bug.

Thanks,
Paul.
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