Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 14 Oct 2019 14:48:02 -0700
From:   Matthew Wilcox <willy@infradead.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Vineet Gupta <vineetg76@gmail.com>,
        linux-arch <linux-arch@vger.kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Peter Zijlstra <peterz@infradead.org>,
        "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Nick Piggin <npiggin@gmail.com>, Linux-MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-snps-arc@lists.infradead.org, Will Deacon <will@kernel.org>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [RFC] asm-generic/tlb: stub out pmd_free_tlb() if
 __PAGETABLE_PMD_FOLDED
Message-ID: <20191014214802.GA32665@bombadil.infradead.org>
References: <20191011121951.nxna6hruuskvdxod@box>
 <20191011223818.7238-1-vgupta@synopsys.com>
 <CAHk-=whLs=TrRzmB9KRLxcPERq0QXPUUkbD8vzKzaDszBcUspg@mail.gmail.com>
 <c0979d98-7236-b7c8-bd40-173ee2e87385@gmail.com>
 <CAHk-=wi3WXpKJkcpgHkUMgLiX9UdXnXhSFzBd8vTWkKgFpz0+Q@mail.gmail.com>
 <8bfd023b-5c00-8355-fd0f-3b4377951e6c@gmail.com>
 <CAHk-=wgUxgA-s4ZvxpcKDFfyoEmvcDr9Ydgo5W4s2hvrLHhP+g@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAHk-=wgUxgA-s4ZvxpcKDFfyoEmvcDr9Ydgo5W4s2hvrLHhP+g@mail.gmail.com>
User-Agent: Mutt/1.12.1 (2019-06-15)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, Oct 14, 2019 at 01:38:34PM -0700, Linus Torvalds wrote:
> And now I've said pgd/pud/p4d/pmd so many times that I've confused
> myself and think I'm wrong again, and I think that historically -
> originally - we always had a pgd, and then the pmd didn't exist
> because it was folded into it. That makes sense from a x86 naming
> standpoint. Then x86 _did_ get a pmd, and then we added more levels in
> between, and other architectures did things differently.

Oh my goodness.  Thank you for writing all this out and finally getting
to this point.  I was reading the whole thing thinking "This is different
from what I remember" and then you got here.  This explains so much about
how our MM does/doesn't work, and it's not just me that's confused ;-)