Messages in this thread | | | Date | Mon, 4 May 2020 18:39:29 -0700 | From | Sean Christopherson <> | Subject | Re: [PATCH] KVM: Fix a warning in __kvm_gfn_to_hva_cache_init() |
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On Mon, May 04, 2020 at 03:05:26PM -0400, Peter Xu wrote: > GCC 10.0.1 gives me this warning when building KVM: > > warning: ‘nr_pages_avail’ may be used uninitialized in this function [-Wmaybe-uninitialized] > 2442 | for ( ; start_gfn <= end_gfn; start_gfn += nr_pages_avail) { > > It should not happen, but silent it.
Heh, third times a charm? This has been reported and proposed twice before[1][2]. Are you using any custom compiler flags? E.g. -O3 is known to cause false positives with -Wmaybe-uninitialized.
If we do end up killing this warning, I'd still prefer to use uninitialized_var() over zero-initializing the variable.
[1] https://lkml.kernel.org/r/20200218184756.242904-1-oupton@google.com [2] https://bugzilla.kernel.org/show_bug.cgi?id=207173
> > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > virt/kvm/kvm_main.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 74bdb7bf3295..2da293885a67 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -2425,7 +2425,7 @@ static int __kvm_gfn_to_hva_cache_init(struct kvm_memslots *slots, > gfn_t start_gfn = gpa >> PAGE_SHIFT; > gfn_t end_gfn = (gpa + len - 1) >> PAGE_SHIFT; > gfn_t nr_pages_needed = end_gfn - start_gfn + 1; > - gfn_t nr_pages_avail; > + gfn_t nr_pages_avail = 0; > > /* Update ghc->generation before performing any error checks. */ > ghc->generation = slots->generation; > -- > 2.26.2 >
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