From: Jakub Kicinski <kuba@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Willem de Bruijn <willemb@google.com>,
David Miller <davem@davemloft.net>,
Jonathan Lemon <jonathan.lemon@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
"the arch/x86 maintainers" <x86@kernel.org>,
Christoph Hellwig <hch@lst.de>,
Matthew Wilcox <willy@infradead.org>,
Daniel Vetter <daniel@ffwll.ch>,
Andrew Morton <akpm@linux-foundation.org>,
Linux-MM <linux-mm@kvack.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Netdev <netdev@vger.kernel.org>
Subject: Re: [BUG] from x86: Support kmap_local() forced debugging
Date: Wed, 6 Jan 2021 17:49:17 -0800 [thread overview]
Message-ID: <20210106174917.3f8ad0d8@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <CAHk-=wh2895wXEXYtb70CTgW+UR7jfh6VFhJB_bOrF0L7UKoEg@mail.gmail.com>
On Wed, 6 Jan 2021 17:03:48 -0800 Linus Torvalds wrote:
> I wonder whether there is other code that "knows" about kmap() only
> affecting PageHighmem() pages thing that is no longer true.
>
> Looking at some other code, skb_gro_reset_offset() looks suspiciously
> like it also thinks highmem pages are special.
>
> Adding the networking people involved in this area to the cc too.
Thanks for the detailed analysis! skb_gro_reset_offset() checks if
kernel can read data in the fragments directly as an optimization,
in case the entire header is in a fragment.
IIUC DEBUG_KMAP_LOCAL_FORCE_MAP only affects the mappings from
explicit kmap calls, which GRO won't make - it will fall back to
pulling the header out of the fragment and end up in skb_copy_bits(),
i.e. the loop you fixed. So GRO should be good. I think..
next prev parent reply other threads:[~2021-01-07 1:50 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-18 19:48 [patch V4 0/8] mm/highmem: Preemptible variant of kmap_atomic & friends Thomas Gleixner
2020-11-18 19:48 ` [patch V4 1/8] mm/highmem: Provide and use CONFIG_DEBUG_KMAP_LOCAL Thomas Gleixner
2020-11-24 14:20 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-18 19:48 ` [patch V4 2/8] mm/highmem: Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP Thomas Gleixner
2020-11-18 21:13 ` Linus Torvalds
2020-11-19 8:46 ` Mel Gorman
2020-11-19 17:19 ` Linus Torvalds
2020-11-24 14:20 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-18 19:48 ` [patch V4 3/8] x86: Support kmap_local() forced debugging Thomas Gleixner
2020-11-24 14:20 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2021-01-06 23:01 ` [BUG] from " Steven Rostedt
2021-01-07 1:03 ` Linus Torvalds
2021-01-07 1:16 ` Steven Rostedt
2021-01-07 1:49 ` Steven Rostedt
2021-01-07 1:49 ` Jakub Kicinski [this message]
2021-01-07 2:11 ` Willem de Bruijn
2021-01-07 4:44 ` Willem de Bruijn
2021-01-07 19:47 ` Linus Torvalds
2021-01-07 20:52 ` Steven Rostedt
2021-01-07 21:07 ` Willem de Bruijn
2020-11-18 19:48 ` [patch V4 4/8] sched: Make migrate_disable/enable() independent of RT Thomas Gleixner
2020-11-19 9:38 ` Mel Gorman
2020-11-19 11:14 ` Peter Zijlstra
2020-11-19 12:14 ` Mel Gorman
2020-11-19 14:17 ` Steven Rostedt
2020-11-19 17:23 ` Linus Torvalds
2020-11-19 18:28 ` Peter Zijlstra
2020-11-20 1:33 ` Thomas Gleixner
2020-11-20 9:29 ` Peter Zijlstra
2020-11-22 23:16 ` Andy Lutomirski
2020-11-23 21:15 ` Thomas Gleixner
2020-11-23 21:25 ` Thomas Gleixner
2020-11-23 22:07 ` Andy Lutomirski
2020-11-23 23:10 ` Thomas Gleixner
2020-11-24 10:29 ` [tip: sched/core] " tip-bot2 for Thomas Gleixner
2020-11-18 19:48 ` [patch V4 5/8] sched: highmem: Store local kmaps in task struct Thomas Gleixner
2020-11-19 11:33 ` Peter Zijlstra
2020-11-19 11:51 ` Peter Zijlstra
2020-11-19 12:12 ` Peter Zijlstra
2020-11-19 14:11 ` Thomas Gleixner
2020-11-24 14:20 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-18 19:48 ` [patch V4 6/8] mm/highmem: Provide kmap_local* Thomas Gleixner
2020-11-24 14:20 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-18 19:48 ` [patch V4 7/8] io-mapping: Provide iomap_local variant Thomas Gleixner
2020-11-24 14:20 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-18 19:48 ` [patch V4 8/8] x86/crashdump/32: Simplify copy_oldmem_page() Thomas Gleixner
2020-11-24 14:20 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-24 8:03 ` [patch V4 0/8] mm/highmem: Preemptible variant of kmap_atomic & friends Peter Zijlstra
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