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

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

[gregkh]

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 <stable@vger.kernel.org> know about it.


>From e27a9eca5d4a392b96ce5d5238c8d637bcb0a52c Mon Sep 17 00:00:00 2001
From: James Cowgill <James.Cowgill@imgtec.com>
Date: Tue, 20 Jun 2017 10:57:51 +0100
Subject: KVM: MIPS: Fix maybe-uninitialized build failure
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: James Cowgill <James.Cowgill@imgtec.com>

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.

Signed-off-by: James Cowgill <James.Cowgill@imgtec.com>
Fixes: 57e3869cfaae ("KVM: MIPS/TLB: Generalise host TLB invalidate to kernel ASID")
Acked-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/arch/mips/kvm/tlb.c
+++ b/arch/mips/kvm/tlb.c
@@ -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 James.Cowgill@imgtec.com are

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