At Thu, 08 Aug 2013 09:16:27 +0200, Clemens Ladisch wrote: > > Takashi Iwai wrote: > > Alan Stern wrote: > >> A buffer _can_ be in the middle of a kmalloc'ed space, but the CPU must > >> not access any of the fields around it that might occupy the same cache > >> line while the buffer is being used for DMA. > > > > Hrm, but does the kmalloc buffer always guarantee such cache line > > exclusiveness...? I thought a simple one like SLOB doesn't care. > > Documentation/DMA-API-HOWTO.txt says: > | Architectures must ensure that kmalloc'ed buffer is > | DMA-safe. Drivers and subsystems depend on it. If an architecture > | isn't fully DMA-coherent (i.e. hardware doesn't ensure that data in > | the CPU cache is identical to data in main memory), > | ARCH_DMA_MINALIGN must be set so that the memory allocator > | makes sure that kmalloc'ed buffer doesn't share a cache line with > | the others. Ah, good, thanks! Takashi -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
