From 79f702a6d18c75760c68202007265b2310d6f44e Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Sun, 3 Jun 2012 11:34:08 +0300 Subject: [PATCH] KVM: disable uninitialized var warning MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit I see this in 3.5-rc1: arch/x86/kvm/mmu.c: In function ‘kvm_test_age_rmapp’: arch/x86/kvm/mmu.c:1271: warning: ‘iter.desc’ may be used uninitialized in this function The line in question was introduced by commit 1e3f42f03c38c29c1814199a6f0a2f01b919ea3f static int kvm_test_age_rmapp(struct kvm *kvm, unsigned long *rmapp, unsigned long data) { - u64 *spte; + u64 *sptep; + struct rmap_iterator iter; <- line 1271 int young = 0; /* The reason I think is that the compiler assumes that the rmap value could be 0, so static u64 *rmap_get_first(unsigned long rmap, struct rmap_iterator *iter) { if (!rmap) return NULL; if (!(rmap & 1)) { iter->desc = NULL; return (u64 *)rmap; } iter->desc = (struct pte_list_desc *)(rmap & ~1ul); iter->pos = 0; return iter->desc->sptes[iter->pos]; } will not initialize iter.desc, but the compiler isn't smart enough to see that for (sptep = rmap_get_first(*rmapp, &iter); sptep; sptep = rmap_get_next(&iter)) { will immediately exit in this case. I checked by adding if (!*rmapp) goto out; on top which is clearly equivalent but disables the warning. This patch uses uninitialized_var to disable the warning without increasing code size. Signed-off-by: Michael S. Tsirkin Signed-off-by: Avi Kivity --- arch/x86/kvm/mmu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 1ca7164a74f1..24dd43d45ae4 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -1238,7 +1238,7 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp, unsigned long data) { u64 *sptep; - struct rmap_iterator iter; + struct rmap_iterator uninitialized_var(iter); int young = 0; /* -- 2.20.1