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Subject: Re: [patch 53/60] x86/mm: Use/Fix PCID to optimize user/kernel
 switches
To: Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>
References: <20171204140706.296109558@linutronix.de>
 <20171204150609.179192470@linutronix.de>
 <CALCETrVw2acfyG6Ck=MnAbKdfvACpAoSpaBx6VZ1jxyzUYgv2Q@mail.gmail.com>
 <20171205220557.GX3165@worktop.lehotels.local>
Cc: Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Borislav Petkov <bpetkov@suse.de>,
        Greg KH <gregkh@linuxfoundation.org>, Kees Cook <keescook@google.com>,
        Hugh Dickins <hughd@google.com>, Brian Gerst <brgerst@gmail.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Denys Vlasenko <dvlasenk@redhat.com>, Rik van Riel <riel@redhat.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Juergen Gross <jgross@suse.com>,
        David Laight <David.Laight@aculab.com>,
        Eduardo Valentin <eduval@amazon.com>, aliguori@amazon.com,
        Will Deacon <will.deacon@arm.com>,
        Daniel Gruss <daniel.gruss@iaik.tugraz.at>
From: Dave Hansen <dave.hansen@intel.com>
Message-ID: <7b6502fa-b5be-b8ab-eb82-fcb0fb906f46@intel.com>
Date: Tue, 5 Dec 2017 14:08:59 -0800
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On 12/05/2017 02:05 PM, Peter Zijlstra wrote:
>> I haven't checked that hard which patch introduces this bug, but it
>> seems that, with this applied, nothing propagates
>> non-mm-switch-related flushes to usermode.  Shouldn't
>> flush_tlb_func_common() contain a call to invalidate_user_asid() near
>> the bottom?  Alternatively, it could be in local_flush_tlb() and
>> __flush_tlb_single() (or whatever the hell the flush-one-usermode-TLB
>> function ends up being called).
> __native_flush_tlb_single() has the invalidate_user_asid()
> __native_flush_tlb() has the invalidate_user_asid().
> 
> Which should be exactly that last option you mention.

I can also see INVPCIDs in profiles, so it's definitely getting used.