powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)

Message ID 87zifatu3a.fsf@concordia.ellerman.id.au
State Accepted
Headers show

Commit Message

Michael Ellerman April 21, 2017, 1:42 a.m.
"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>

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(-)

Comments

Paul E. McKenney April 21, 2017, 4:17 a.m. | #1
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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Paolo Bonzini April 21, 2017, 7:27 a.m. | #2
On 21/04/2017 06:17, Paul E. McKenney wrote:
>> 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.  ;-)

Sure,

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

since I don't expect conflicts between whoever applies this patch and
the KVM tree.

Paolo
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Paul E. McKenney April 21, 2017, 12:51 p.m. | #3
On Fri, Apr 21, 2017 at 09:27:59AM +0200, Paolo Bonzini wrote:
> 
> 
> On 21/04/2017 06:17, Paul E. McKenney wrote:
> >> 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.  ;-)
> 
> Sure,
> 
> Acked-by: Paolo Bonzini <pbonzini@redhat.com>
> 
> since I don't expect conflicts between whoever applies this patch and
> the KVM tree.

Applied, thank you!

							Thanx, Paul

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Michael Ellerman April 22, 2017, 6:09 a.m. | #4
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com> writes:
> On Fri, Apr 21, 2017 at 09:27:59AM +0200, Paolo Bonzini wrote:
>> On 21/04/2017 06:17, Paul E. McKenney wrote:
>> >> 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.  ;-)
>> 
>> Sure,
>> 
>> Acked-by: Paolo Bonzini <pbonzini@redhat.com>
>> 
>> since I don't expect conflicts between whoever applies this patch and
>> the KVM tree.
>
> Applied, thank you!

Thanks all.

cheers

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Patch

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, ...) \