Jan Beulich writes ("Re: [PATCH for-4.16] x86/shstk: Fix use of shadow stacks
with XPTI active"):
> On 02.11.2021 15:39, Andrew Cooper wrote:
> > The call to setup_cpu_root_pgt(0) in smp_prepare_cpus() is too early. It
> > clones the BSP's stack while the .data mapping is still in use, causing all
> > mappings to be fully read read/write (and with no guard pages either). This
> > ultimately causes #DF when trying to enter the dom0 kernel for the first
> > time.
> >
> > Defer setting up BSPs XPTI pagetable until reinit_bsp_stack() after we've
> > set
> > up proper shadow stack permissions.
> >
> > Fixes: 60016604739b ("x86/shstk: Rework the stack layout to support shadow
> > stacks")
> > Fixes: b60ab42db2f0 ("x86/shstk: Activate Supervisor Shadow Stacks")
> > Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
>
> Reviewed-by: Jan Beulich <jbeul...@suse.com>
Release-Acked-by: Ian Jackson <i...@xenproject.org>
