Re: [PATCH 3/3] x86: mm: add x86_64 support for page table check

[Jiri Slaby]

On 01. 12. 21, 14:55, Pasha Tatashin wrote:
> On Wed, Dec 1, 2021 at 3:44 AM Jiri Slaby <jirislaby@xxxxxxxxxx> wrote:
> > On 01. 12. 21, 9:00, Jiri Slaby wrote:
> > > On 23. 11. 21, 22:48, Pasha Tatashin wrote:
> > > > Add page table check hooks into routines that modify user page tables.
> > >
> > > Hi,
> > >
> > > I bisected to this as this causes crashes during modules load:
> >
> > And it's not enough to unset CONFIG_PAGE_TABLE_CHECK_ENFORCED. I had to
> > unset CONFIG_PAGE_TABLE_CHECK completely to get rid of this.
>
> Hi,
>
> Thanks for reporting this. Seems like module load for some reasons
> does not like the static branches. However, I was not able to repro
> this. Could you please share your config and the module that you were
> loading?

It's the openSUSE's -next config:
https://raw.githubusercontent.com/openSUSE/kernel-source/linux-next/config/x86_64/vanilla

But with CONFIG_IWLMEI=n (as that fails to link).

One has to load i915, other modules (71 on my system) are apparently fine.

i915 tries to patch your `page_table_check_disabled' which is defined as 
`DEFINE_STATIC_KEY_TRUE_RO':
> jump_label_add_module: key=__tracepoint_mmap_lock_released 
(ffffffff93f36d88) mod=0000000000000000
> jump_label_add_module: key=hugetlb_free_vmemmap_enabled_key 
(ffffffff94873560) mod=0000000000000000
> jump_label_add_module: key=devmap_managed_key (ffffffff94902700) 
mod=0000000000000000
> jump_label_add_module: key=page_table_check_disabled 
(ffffffff939da760) mod=0000000000000000
> BUG: unable to handle page fault for address: ffffffff939da768

regards,
--
js
suse labs