Re: [kvm-unit-tests PATCH 01/14] x86: vm: allow multiple init for vm setup

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On Thu, Oct 20, 2016 at 04:24:08PM +0800, Peter Xu wrote:
> On Thu, Oct 20, 2016 at 10:17:07AM +0200, Andrew Jones wrote:
> > On Fri, Oct 14, 2016 at 08:40:39PM +0800, Peter Xu wrote:
> > > Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
> > > ---
> > >  lib/x86/vm.c | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > > 
> > > diff --git a/lib/x86/vm.c b/lib/x86/vm.c
> > > index 906fbf2..9771bd7 100644
> > > --- a/lib/x86/vm.c
> > > +++ b/lib/x86/vm.c
> > > @@ -151,9 +151,16 @@ static void setup_mmu(unsigned long len)
> > >  
> > >  void setup_vm()
> > >  {
> > > +    static bool vm_inited = false;
> > > +
> > > +    if (vm_inited) {
> > > +        return;
> > > +    }
> > > +
> > >      end_of_memory = fwcfg_get_u64(FW_CFG_RAM_SIZE);
> > >      free_memory(&edata, end_of_memory - (unsigned long)&edata);
> > >      setup_mmu(end_of_memory);
> > > +    vm_inited = true;
> > >  }
> > >  
> > >  void *vmalloc(unsigned long size)
> > > -- 
> > > 2.7.4
> > >
> > 
> > My preference for kvm-unit-tests is that we avoid tolerating
> > unit tests that do things "wrong". This patch allows setup_vm
> > to be called multiple times, but why do that? Why not just
> > ensure it's only called once? If it looks like a mistake that's
> > easy to make and hard to debug, then maybe we need an assert
> > 
> >  assert(!end_of_memory); /* ensure we haven't already called setup_vm */
> > 
> > or something.
> 
> Yeah, sure. The first two patches are just something good to have IMO,
> I did it since I see we have similar thing in setup_idt(), and I feel
> it good. I can replace it with an assertion.

Let's do these patches separate from the series and maybe change setup_idt
too? It'd be interesting to see if the assert in setup_idt would fire,
i.e. if any users are relying on it being tolerant to multiple calls, and
then find out why.

drew
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