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SubjectRe: powerpc KVM build break in linux-next (was Re: [PATCH tip/core/rcu 40/40] srcu: Parallelize callback handling)
"Paul E. McKenney" <> 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" <> 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 <>


From a19a6617e2817e485ccc2f7cc5a97bd7ff769b87 Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <>
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 <>
Reported-by: Michael Ellerman <>
Reported-by: kbuild test robot <>
Suggested-by: Paolo Bonzini <>
Signed-off-by: Paul E. McKenney <>
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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