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SubjectRe: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)
On Fri, Apr 21, 2017 at 11:42:01AM +1000, Michael Ellerman wrote:
> "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> writes:
> > On Thu, Apr 20, 2017 at 05:28:32PM +0200, Paolo Bonzini wrote:
> >> On 20/04/2017 05:40, Michael Ellerman wrote:
> >> > "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> writes:
> >> >
> >> > This change seems to have had the non-obvious effect of breaking the
> >> > powerpc KVM build.
> ...
> >>
> >> Michael, if you want to move the two srcu structs at the end of struct
> >> kvm, that would be fine by me. Please send a patch yourself so you can
> >> test it on PPC. Thanks,
> >
> > On the off-chance that it is at all helpful, I have added the commit
> > shown below to -rcu.
>
> As shown below :)
>
> > If it helps, I am happy to push this, but am just as happy to drop it
> > in favor of some other fix. If at all possible, I would like to get
> > this into the upcoming merge window.
>
> Thanks, this looks perfect to me, and if you're happy to put it on top
> of your tree that would limit the breakage to a smaller history window,
> so that would be ideal.
>
> Tested-by: Michael Ellerman <mpe@ellerman.id.au>

Thank you, Michael!

Paolo, does this look good to you? My upstream maintainer will be much
more likely to take this with your ack. ;-)

Thanx, Paul

> cheers
>
>
> >From a19a6617e2817e485ccc2f7cc5a97bd7ff769b87 Mon Sep 17 00:00:00 2001
> From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> Date: Thu, 20 Apr 2017 17:30:06 -0700
> Subject: kvm: Move srcu_struct fields to end of struct kvm
>
> Parallelizing SRCU callback handling increased the size of srcu_struct,
> which moved the kvm_arch field within the kvm struct out of reach of
> powerpc's current assembly code, resulting in the following sort of
> build error:
>
> arch/powerpc/kvm/book3s_hv_rmhandlers.S:617: Error: operand out of range (0x000000000000b328 is not between 0xffffffffffff8000 and 0x0000000000007fff)
>
> This commit moves the srcu_struct fields in the kvm structure to follow
> the kvm_arch field, which again allows powerpc's assembly code to
> reach it.
>
> Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
> Reported-by: Michael Ellerman <michaele@au1.ibm.com>
> Reported-by: kbuild test robot <fengguang.wu@intel.com>
> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> ---
> include/linux/kvm_host.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 2c14ad9..96c8e29 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -375,8 +375,6 @@ struct kvm {
> struct mutex slots_lock;
> struct mm_struct *mm; /* userspace tied to this vm */
> struct kvm_memslots *memslots[KVM_ADDRESS_SPACE_NUM];
> - struct srcu_struct srcu;
> - struct srcu_struct irq_srcu;
> struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
>
> /*
> @@ -429,6 +427,8 @@ struct kvm {
> struct list_head devices;
> struct dentry *debugfs_dentry;
> struct kvm_stat_data **debugfs_stat_data;
> + struct srcu_struct srcu;
> + struct srcu_struct irq_srcu;
> };
>
> #define kvm_err(fmt, ...) \
> --
> cgit v1.1

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