On Wed, Aug 11, 2021, Babu Moger wrote: > > On 8/11/21 2:09 AM, Paolo Bonzini wrote: > > On 11/08/21 01:38, Babu Moger wrote: > >> No. This will not work. The PKU feature flag is bit 30. That is 2^30 > >> iterations to cover the tests for this feature. Looks like I need to split > >> the tests into PKU and non PKU tests. For PKU tests I may need to change > >> the bump frequency (in ac_test_bump_one) to much higher value. Right now, > >> it is 1. Let me try that, > > > > The simplest way to cut on tests, which is actually similar to this patch, > > would be: > > > > - do not try all combinations of PTE access bits when reserved bits are set > > > > - do not try combinations with more than one reserved bit set > > Did you mean this? Just doing this reduces the combination by huge number. > I don't need to add your first PTE access combinations. > > diff --git a/x86/access.c b/x86/access.c > index 47807cc..a730b6b 100644 > --- a/x86/access.c > +++ b/x86/access.c > @@ -317,9 +317,7 @@ static _Bool ac_test_legal(ac_test_t *at) > /* > * Shorten the test by avoiding testing too many reserved bit > combinations > */ > - if ((F(AC_PDE_BIT51) + F(AC_PDE_BIT36) + F(AC_PDE_BIT13)) > 1) > - return false; > - if ((F(AC_PTE_BIT51) + F(AC_PTE_BIT36)) > 1) > + if ((F(AC_PDE_BIT51) + F(AC_PDE_BIT36) + F(AC_PDE_BIT13) + > F(AC_PTE_BIT51) + F(AC_PTE_BIT36)) > 1) > return false; > > return true; Looks good to me, is it sufficient to keep the overall runtime sane?. And maybe update the comment too, e.g. something like /* * Skip testing multiple reserved bits to shorten the test. Reserved * bit page faults are terminal and multiple reserved bits do not affect * the error code; the odds of a KVM bug are super low, and the odds of * actually being able to detect a bug are even lower. */
