On Thu, May 02, 2019 at 08:40:38AM -0700, nadav.amit@xxxxxxxxx wrote: > From: Nadav Amit <nadav.amit@xxxxxxxxx> > > One of the most important properties of tests is reproducibility. For > tests to be reproducible, the same environment should be set on each > test invocation. > > When it comes to memory content, this is not exactly the case in > kvm-unit-tests. The tests might, mistakenly or intentionally, assume > that memory is zeroed, which apparently is the case after seabios runs. > However, failures might not be reproducible if this assumption is > broken. > > As an example, consider x86 do_iret(), which mistakenly does not push > SS:RSP onto the stack on 64-bit mode, although they are popped > unconditionally. > > Do not assume that memory is zeroed. Clear it once it is allocated to > allow tests to easily be reproducible. > > Signed-off-by: Nadav Amit <nadav.amit@xxxxxxxxx> > --- > lib/alloc_page.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/lib/alloc_page.c b/lib/alloc_page.c > index 730f2b5..b0f4515 100644 > --- a/lib/alloc_page.c > +++ b/lib/alloc_page.c > @@ -65,6 +65,7 @@ void *alloc_page() > freelist = *(void **)freelist; > spin_unlock(&lock); > > + memset(p, 0, PAGE_SIZE); > return p; > } > > -- > 2.17.1 > I think this is reasonable, but if we make this change then we should remove the now redundant page zeroing too. A quick grep shows 20 instances $ git grep -A1 alloc_page | grep memset | grep 0, | wc -l 20 There may be more. Thanks, drew
