Messages in this thread | | | Date | Thu, 16 Oct 2014 10:34:01 -0700 | From | Benjamin Poirier <> | Subject | Re: Regarding tx-nocache-copy in the Sheevaplug |
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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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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