On Thu, Oct 04, 2012 at 09:19:04PM +1000, Benjamin Herrenschmidt wrote: > On Sun, 2012-09-30 at 17:28 -0600, Jason Gunthorpe wrote: > > asm/page.h discusses the calculation for v2p and p2v, it should be: > > va = pa + KERNELBASE - PHYSICAL_START > > which is the same as: > > va = pa + LOAD_OFFSET > > > > tophys/tovirt were using PAGE_OFFSET, which as page.h says, is almost > > always the same thing. > > > > Signed-off-by: Jason Gunthorpe <jguntho...@obsidianresearch.com> > > It's a bit gross tho in that KERNEL_BASE, PHYSICAL_START and LOAD_OFFSET > are about where the kernel is linked/running, and while the value ends > up happening to also be the p->v offset (and indeed not by accident), it > makes the code less clear and more confusing.
Yes, I found the three names confusing.. However LOAD_OFFSET is the name that include/asm-generic/vmlinux.lds.h and many arch's use for P2V translation in the linker script, so at least there is some precedent. > I don't have the bandwidth to revisit all that, but I really think that > whole are area where PAGE_OFFSET doesn't map 0 needs revisiting. Something like that is also outside my scope.. This patch does fix a bug I hit when CONFIG_PHYSICAL_START is used, are there problems with it in other cases? FWIW, this is part of a larger work that makes CONFIG_PHYSICAL_START work on PPC404, which is not yet clean enough to post: https://github.com/jgunthorpe/linux/commit/90df2d247c9db5d39c32dbbada0815f15d7b3be7 Regards, Jason _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
