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. Regards, Clemens -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
