-------- Original-Nachricht -------- > Datum: Thu, 26 Jun 2008 17:29:05 +0800 > Von: Andrew Lewis <[EMAIL PROTECTED]> > An: linuxppc-dev@ozlabs.org > CC: \'Andrew Lewis\' <[EMAIL PROTECTED]>, [EMAIL PROTECTED] > Betreff: [PATCH/RFC] powerpc: prevent memory corruption due to cache > invalidation of unaligned DMA buffer
> On PowerPC processors with non-coherent cache architectures the DMA > subsystem calls invalidate_dcache_range() before performing a DMA read > operation. If the address and length of the DMA buffer are not aligned > to a cache-line boundary this can result in memory outside of the DMA > buffer being invalidated in the cache. If this memory has an > uncommitted store then the data will be lost and a subsequent read of > that address will result in an old value being returned from main memory. > > Only when the DMA buffer starts on a cache-line boundary and is an exact > mutiple of the cache-line size can invalidate_dcache_range() be called, > otherwise flush_dcache_range() must be called. flush_dcache_range() > will first flush uncommitted writes, and then invalidate the cache. I have a similar problem, but with a network driver (which uses cacheable skbuffers as DMA memory). The SLUB allocator should return cache line aligned memory, but that doesn't prevent data corruption. I fixed it by setting NET_SKB_PAD (default 16) to L1_CACHE_BYTES (32 on my 7455 non coherent DMA system). It looks like your patch could solve my problem without changing NET_SKB_PAD. I'll have to try that out. regards, Gerhard -- Ist Ihr Browser Vista-kompatibel? Jetzt die neuesten Browser-Versionen downloaden: http://www.gmx.net/de/go/browser _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
