On Thu, Apr 11, 2019 at 06:41:05AM -0700, Sean Christopherson wrote: > On Wed, Apr 10, 2019 at 02:13:34PM -0700, Nadav Amit wrote: > > Untested, but clearly bit 12 is the one that needs to be tested. > > > > Signed-off-by: Nadav Amit <nadav.amit@xxxxxxxxx> > > --- > > x86/cstart64.S | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/x86/cstart64.S b/x86/cstart64.S > > index 21db10f..8626f02 100644 > > --- a/x86/cstart64.S > > +++ b/x86/cstart64.S > > @@ -243,7 +243,7 @@ start64: > > setup_5level_page_table: > > /* Check if 5-level paging has already enabled */ > > mov %cr4, %rax > > - test $12, %eax > > + bt $12, %eax > > jnz lvl5 > > Unfortunately BT doesn't affect RFLAGS.ZF, so 'jnz' needs to be changed > to 'jc'. Or alternatively, do 'test $1000, %eax'. And of course that should be $0x1000...
