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Date: Thu, 30 Nov 2017 14:13:53 +0100
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 6/6] x86/mm/kaiser: Optimize __native_flush_tlb
Message-ID: <20171130131353.zqiywe532kjca4pj@hirez.programming.kicks-ass.net>
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To: linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>, Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>, Denys Vlasenko <dvlasenk@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, Josh Poimboeuf <jpoimboe@redhat.com>, Linus Torvalds <torvalds@linux-foundation.org>, Rik van Riel <riel@redhat.com>, daniel.gruss@iaik.tugraz.at, hughd@google.com, keescook@google.com, linux-mm@kvack.org, michael.schwarz@iaik.tugraz.at, moritz.lipp@iaik.tugraz.at, richard.fellner@student.tugraz.at

On Thu, Nov 30, 2017 at 01:43:19PM +0100, Peter Zijlstra wrote:
> Now the problem is that flush_tlb_kernel_range() is implemented using
> either __flush_tlb_all() or __flush_tlb_single(), and it is that last
> use that is buggered.
> 
> So at the very least we need the below to cure things, but there is
> another inconsistency; do_flush_tlb_all() is used by both
> flush_tlb_all() and flush_tlb_kernel_range() and increments NR_TLB_*,
> do_kernel_range_flush() OTOH does not increment NR_TLB_*. I'm not fixing
> that, but I'll leave a comment around or something, so we can later try
> and figure out what exact statistics we want.

Alternatively, we'd simply kill the entire invlpg path for
flush_tlb_kernel_range() and simply do __flush_tlb_all().

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