Re: [kvm-unit-tests PATCH v1 2/2] lib/alloc_page: Fix compilation issue on 32bit archs

[Sean Christopherson <sean.j.christopherson@intel.com>]

On Tue, Jul 14, 2020 at 01:41:23PM +0200, Claudio Imbrenda wrote:
> On Tue, 14 Jul 2020 13:20:16 +0200
> Thomas Huth <thuth@redhat.com> wrote:
> 
> > On 14/07/2020 13.09, Claudio Imbrenda wrote:
> > > The assert in lib/alloc_page is hardcoded to long, and size_t is
> > > just an int on 32 bit architectures.
> > > 
> > > Adding a cast makes the compiler happy.
> > > 
> > > Fixes: 73f4b202beb39 ("lib/alloc_page: change some parameter types")
> > > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> > > ---
> > >  lib/alloc_page.c | 5 +++--
> > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/lib/alloc_page.c b/lib/alloc_page.c
> > > index fa3c527..617b003 100644
> > > --- a/lib/alloc_page.c
> > > +++ b/lib/alloc_page.c
> > > @@ -29,11 +29,12 @@ void free_pages(void *mem, size_t size)
> > >  	assert_msg((unsigned long) mem % PAGE_SIZE == 0,
> > >  		   "mem not page aligned: %p", mem);
> > >  
> > > -	assert_msg(size % PAGE_SIZE == 0, "size not page aligned:
> > > %#lx", size);
> > > +	assert_msg(size % PAGE_SIZE == 0, "size not page aligned:
> > > %#lx",
> > > +		(unsigned long)size);
> > >  
> > >  	assert_msg(size == 0 || (uintptr_t)mem == -size ||
> > >  		   (uintptr_t)mem + size > (uintptr_t)mem,
> > > -		   "mem + size overflow: %p + %#lx", mem, size);
> > > +		   "mem + size overflow: %p + %#lx", mem,
> > > (unsigned long)size);  
> > 
> > Looking at lib/printf.c, it seems like it also supports %z ... have
> > you tried?
> 
> no, but in hindsight I should have. It's probably a much cleaner
> solution. I'll try and respin.

I'm not opposed to using size_t, but if we go that route then the entirety
of alloc_page.c should be converted to size_t.  As is, there is code like:

	void free_pages_by_order(void *mem, unsigned int order)
	{
        	free_pages(mem, 1ul << (order + PAGE_SHIFT));
	}

and

	void *alloc_pages(unsigned int order)
	{
		...

		/* Looking for a run of length (1 << order). */
		unsigned long run = 0;
		const unsigned long n = 1ul << order;
		const unsigned long align_mask = (n << PAGE_SHIFT) - 1;
		void *run_start = NULL;
		void *run_prev = NULL;
		unsigned long run_next_pa = 0;
		unsigned long pa;

		assert(order < sizeof(unsigned long) * 8);

		...
	}

that very explicitly uses 'unsigned long' for the size.