From: Benjamin Poirier <benjamin.poirier@gmail.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: "Lluís Batlle i Rossell" <viric@viric.name>,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
"Carles Pagès" <page@cubata.homelinux.net>,
linux-arm-kernel@lists.infradead.org
Subject: Re: Regarding tx-nocache-copy in the Sheevaplug
Date: Thu, 16 Oct 2014 10:34:01 -0700 [thread overview]
Message-ID: <20141016173401.GA16515@f1.synalogic.ca> (raw)
In-Reply-To: <1413413127.17186.5.camel@edumazet-glaptop2.roam.corp.google.com>
On 2014/10/15 15:45, Eric Dumazet wrote:
> On Wed, 2014-10-15 at 14:57 -0700, Benjamin Poirier wrote:
> > On 2014/10/13 12:52, Lluís Batlle i Rossell wrote:
> > > Hello,
> > >
> > > on the 7th of January 2014 ths patch was applied:
> > > https://lkml.org/lkml/2014/1/7/307
> > >
> > > [PATCH v2] net: Do not enable tx-nocache-copy by default
> > >
> > > In the Sheevaplug (ARM Feroceon 88FR131 from Marvell) this made packets to be
> > > sent corrupted. I think this machine has something special about the cache.
> > >
> > > Enabling back this tx-nocache-copy (as it used to be before the patch) the
> > > transfers work fine again. I think that most people, encountering this problem,
> > > completely disable the tx offload instead of enabling back this setting.
> > >
> > > Is this an ARM kernel problem regarding this platform?
> >
> > This is odd, only x86 defines ARCH_HAS_NOCACHE_UACCESS. On arm,
> > skb_do_copy_data_nocache() should end up using __copy_from_user()
> > regardless of tx-nocache-copy.
>
> kmap_atomic()/kunmap_atomic() is missing, so we lack
> __cpuc_flush_dcache_area() operations.
>
You lost me there.
1) I don't see the link
2) It seems kmap_atomic and so on are there:
$ grep kmap_atomic System.map-3.16-2-kirkwood
c0014838 T kmap_atomic
c001491c T kmap_atomic_pfn
c00149a4 T kmap_atomic_to_page
MACH_KIRKWOOD selects CPU_FEROCEON which has
__cpuc_flush_dcache_area ->
cpu_cache.flush_kern_dcache_area ->
feroceon_flush_kern_dcache_area
next prev parent reply other threads:[~2014-10-16 17:34 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-13 10:52 Regarding tx-nocache-copy in the Sheevaplug Lluís Batlle i Rossell
2014-10-13 12:26 ` Eric Dumazet
2014-10-13 12:32 ` Lluís Batlle i Rossell
2014-10-13 14:21 ` Andrew Lunn
2014-10-13 14:31 ` Lluís Batlle i Rossell
2014-10-13 14:49 ` Eric Dumazet
2014-10-13 15:48 ` Lluís Batlle i Rossell
2014-10-15 21:57 ` Benjamin Poirier
2014-10-15 22:45 ` Eric Dumazet
2014-10-16 17:34 ` Benjamin Poirier [this message]
2014-10-16 17:46 ` Lluís Batlle i Rossell
2014-10-17 20:55 ` Benjamin Poirier
2014-10-16 17:48 ` Eric Dumazet
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