Messages in this thread | | | Date | Thu, 7 Sep 2017 09:48:34 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 1/2] x86/mm: Reinitialize TLB state on hotplug and resume |
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* Jiri Kosina <jikos@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 <torvalds@linux-foundation.org> > > Reported-by: Jiri Kosina <jikos@kernel.org> > > Fixes: 10af6235e0d3 ("x86/mm: Implement PCID based optimization: try to preserve old TLB entries using PCID") > > Signed-off-by: Andy Lutomirski <luto@kernel.org> > > Tested-by: Jiri Kosina <jkosina@suse.cz>
The fix should be upstream already, as of 1c9fe4409ce3 and later.
Thanks,
Ingo
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