linux-kernel - Re: [PATCH 15/24] x86/mm: Allow flushing for future ASID switches

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Message-ID: <CALCETrWyYSM5E17oYQtyc8TKEKHUiTqVApUtw5K-pBw3K3b6wg@mail.gmail.com>
Date:   Thu, 30 Nov 2017 13:51:25 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 15/24] x86/mm: Allow flushing for future ASID switches

On Thu, Nov 30, 2017 at 12:01 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Thu, Nov 30, 2017 at 10:48:56AM -0800, Andy Lutomirski wrote:
>> Should it be tlb_flush_shared_nonglobals_if_kernel_and_user_pagetables_are_separate()?
>
> Its effectively invpcid_flush_all_other() or something like that. Of
> course, its not invpcid based, so we should not name it such.
>
> flush_asid_other() ?

How about mark_other_asids_invalid()?  It doesn't actually flush
anything.  And the caller could be:

if (!kernel_ptes_are_global()) {
  /* nothing to do.  INVLPG flushes global mappings for all ASIDs. */
} else {
  /* There is no efficient way to invalidate a given VA for all ASIDs
simultaneously. */
  mark_other_asids_invalid();
}