On Thu, Jun 30, 2016 at 12:39:03PM +0100, Robin Murphy wrote: > On 30/06/16 12:10, Masahiro Yamada wrote: > > Hello. > > > > Which memory attribute will ARM/ARM64 Linux > > set to the memory region reserved by > > /memreserve/ of Device Tree? > > > > > > Normal memory non-cacheable? > > Or, cacheable? > > Or, not defined? > > > > Perhaps actual behavior depends on whether the reserved area is > > located in the low-memory region? > > Isn't the point of memreserve that the kernel avoids mapping it at all? Not quite. A /memreserve/ allows the kernel to map a region, so long as it doesn't use the region for general allocation. While not strictly defined for arm64 today, in practice the kernel may map a region with Normal Inner-Shareable Inner-WB Outer-WB attributes, following similar behaviour for PPC as defined in ePAPR. Generally I would advise against the use of a memreserve, and favour carving memory out of memory nodes as required, as that imposes stricter requirements. > If a reserved region is later mapped in by a driver using > dma_declare_coherent_memory(), ioremap(), memremap() or whatever else, > then the attributes will vary depending on the exact method used. Indeed. This applies even with the above. Thanks, Mark. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
