Re: [kvm-unit-tests PATCH 4/5] s390x: smp: Allocate memory in DMA31 space

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Fri, 14 Jan 2022 14:13:01 +0100
Janosch Frank <frankja@linux.ibm.com> wrote:

> On 1/14/22 14:01, Claudio Imbrenda wrote:
> > On Fri, 14 Jan 2022 13:50:52 +0100
> > Nico Boehr <nrb@linux.ibm.com> wrote:
> >   
> >> On Fri, 2022-01-14 at 10:02 +0000, Janosch Frank wrote:  
> >>> The store status at address order works with 31 bit addresses so
> >>> let's
> >>> use them.
> >>>
> >>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> >>> ---
> >>>   s390x/smp.c | 4 ++--
> >>>   1 file changed, 2 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/s390x/smp.c b/s390x/smp.c
> >>> index 32f128b3..c91f170b 100644
> >>> --- a/s390x/smp.c
> >>> +++ b/s390x/smp.c  
> >>
> >> [...]
> >>  
> >>> @@ -244,7 +244,7 @@ static void test_func_initial(void)
> >>>   
> >>>   static void test_reset_initial(void)
> >>>   {
> >>> -       struct cpu_status *status = alloc_pages(0);
> >>> +       struct cpu_status *status = alloc_pages_flags(1, AREA_DMA31);  
> >>
> >> Why do we need two pages now?  
> > 
> > actually, wait.....
> > 
> >          struct cpu_status *status = alloc_pages_flags(1, AREA_DMA31);
> >          uint32_t r;
> > 
> >          report_prefix_push("store status at address");
> >          memset(status, 0, PAGE_SIZE * 2);
> > 
> > we were allocating one page, and using 2!
> > 
> > @Janosch do we need 1 or 2 pages?
> >   
> 
> Have a look at the memcmp() below those lines.
> 
> I test if the status page has changed by doing a memcmp against the 
> second page.

so we do need 2 pages, and using 1 was a bug