* Jiri Kosina <ji...@kernel.org> wrote:
> On Wed, 6 Sep 2017, Andy Lutomirski wrote:
>
> > When Linux brings a CPU down and back up, it switches to init_mm and then
> > loads swapper_pg_dir into CR3. With PCID enabled, this has the side effect
> > of masking off the ASID bits in CR3.
> >
> > This can result in some confusion in the TLB handling code. If we
> > bring a CPU down and back up with any ASID other than 0, we end up
> > with the wrong ASID active on the CPU after resume. This could
> > cause our internal state to become corrupt, although major
> > corruption is unlikely because init_mm doesn't have any user pages.
> > More obviously, if CONFIG_DEBUG_VM=y, we'll trip over an assertion
> > in the next context switch. The result of *that* is a failure to
> > resume from suspend with probability 1 - 1/6^(cpus-1).
> >
> > Fix it by reinitializing cpu_tlbstate on resume and CPU bringup.
> >
> > Reported-by: Linus Torvalds <torva...@linux-foundation.org>
> > Reported-by: Jiri Kosina <ji...@kernel.org>
> > Fixes: 10af6235e0d3 ("x86/mm: Implement PCID based optimization: try to
> > preserve old TLB entries using PCID")
> > Signed-off-by: Andy Lutomirski <l...@kernel.org>
>
> Tested-by: Jiri Kosina <jkos...@suse.cz>
The fix should be upstream already, as of 1c9fe4409ce3 and later.
Thanks,
Ingo
