Messages in this thread | | | Date | Thu, 7 Sep 2017 09:31:07 +0200 (CEST) | From | Jiri Kosina <> | Subject | Re: [PATCH 1/2] x86/mm: Reinitialize TLB state on hotplug and resume |
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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>
Thanks,
-- Jiri Kosina SUSE Labs
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