Patch "KVM: MIPS: Fix maybe-uninitialized build failure" has been added to the 4.11-stable tree

This is a note to let you know that I've just added the patch titled

KVM: MIPS: Fix maybe-uninitialized build failure

to the 4.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-mips-fix-maybe-uninitialized-build-failure.patch
and it can be found in the queue-4.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: James Cowgill <[email protected]>
Date: Tue, 20 Jun 2017 10:57:51 +0100
Subject: KVM: MIPS: Fix maybe-uninitialized build failure
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From: James Cowgill <[email protected]>

commit e27a9eca5d4a392b96ce5d5238c8d637bcb0a52c upstream.

This commit fixes a "maybe-uninitialized" build failure in arch/mips/kvm/tlb.c when KVM, DYNAMIC_DEBUG and JUMP_LABEL are all enabled. The failure is:

In file included from ./include/linux/printk.h:329:0,

                 from ./include/linux/kernel.h:13,
                 from ./include/asm-generic/bug.h:15,
                 from ./arch/mips/include/asm/bug.h:41,
                 from ./include/linux/bug.h:4,
                 from ./include/linux/thread_info.h:11,
                 from ./include/asm-generic/current.h:4,
                 from ./arch/mips/include/generated/asm/current.h:1,
                 from ./include/linux/sched.h:11,
                 from arch/mips/kvm/tlb.c:13:

arch/mips/kvm/tlb.c: In function ‘kvm_mips_host_tlb_inv’:
./include/linux/dynamic_debug.h:126:3: error: ‘idx_kernel’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
__dynamic_pr_debug(&descriptor, pr_fmt(fmt), \
^~~~~~~~~~~~~~~~~~
arch/mips/kvm/tlb.c:169:16: note: ‘idx_kernel’ was declared here

  int idx_user, idx_kernel;
                ^~~~~~~~~~

There is a similar error relating to "idx_user". Both errors were observed with GCC 6.

As far as I can tell, it is impossible for either idx_user or idx_kernel to be uninitialized when they are later read in the calls to kvm_debug, but to satisfy the compiler, add zero initializers to both variables.

---
 arch/mips/kvm/tlb.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

@@ -147,7 +147,11 @@ static int _kvm_mips_host_tlb_inv(unsign
 int kvm_mips_host_tlb_inv(struct kvm_vcpu *vcpu, unsigned long va,
 			  bool user, bool kernel)
 {
-	int idx_user, idx_kernel;
+	/*
+	 * Initialize idx_user and idx_kernel to workaround bogus
+	 * maybe-initialized warning when using GCC 6.
+	 */
+	int idx_user = 0, idx_kernel = 0;
 	unsigned long flags, old_entryhi;
 
 	local_irq_save(flags);

Patches currently in stable-queue which might be from [email protected] are

queue-4.11/kvm-mips-fix-maybe-uninitialized-build-failure.patch