linux-kernel - Re: [GIT PULL] MIPS changes for v5.8-rc1

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Date:   Wed, 3 Jun 2020 14:00:03 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Bibo Mao <maobibo@...ngson.cn>
Cc:     linux-mips@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] MIPS changes for v5.8-rc1

On Tue, Jun 2, 2020 at 5:55 AM Thomas Bogendoerfer
<tsbogend@...ha.franken.de> wrote:
>
> Bibo Mao (4):
>       mm/memory.c: Add memory read privilege on page fault handling

Hmm. That's a horribly named commit, but can you clarify why this
didn't just use the existing pte_mkyoung?

These are all paths that set the dirty bit early if it's a write, I
don't see why they wouldn't set the accessed bit too.

Even on architectures that manage the accessed bit in hardware, this
might be a (tiny) performance advantage because it avoids a page table
walker microfault to set the bit when it's accessed.

We already do the pte_mkyoung() in paths like cow_user_page(), so the
others may have been just oversights?

Or was there possibly some reason we didn't want to do it here?

                Linus