On Tue, Jul 31, 2012 at 08:50:02PM +0000, Arnd Bergmann wrote: > On Tuesday 31 July 2012, Russell King - ARM Linux wrote: > > I still fail to see how not having highmem enabled would ever cause memory > > corruption errors (unless something dealing with memory in a very very > > wrong way - iow, not using one of the reservation or memory allocation > > methods provided by the kernel.) > > The problem is that all users of ux500 systems pass a command line like > > vmalloc=256M mem=128M@0 mali.mali_mem=32M@128M hwmem=168M@160M mem=48M@328M > mem_issw=1M@383M mem=640M@384M > > This is of course totally bogus and should not be done. If I understand > Lee correctly, one of the issues resulting from passing a command > line like this without enabling highmem is memory corruption.
But the question is _why_ does that corruption happen. >From the above, we will end up with the kernel getting: 0x00000000 - 0x07ffffff (128M @ 0) 0x14800000 - 0x177fffff (48M @ 328M) 0x18000000 - 0x3fffffff (640M @ 384M) with: 0x08000000 - 0x081fffff used for mali 0x0a000000 - 0x147fffff used for hwmem 0x17f00000 - 0x17ffffff used for mem_issw Now, with highmem disabled, the kernel should still map exactly the regions: 0x00000000 - 0x07ffffff, 0x14800000 - 0x177fffff, into the direct mapped region, and truncate the 0x18000000 - 0x3fffffff region appropriately, reducing the amount of memory available such that it won't overlap the vmalloc area (which you've specified to be a minimum of 256M.) This should _NOT_ cause any memory corruption. So, come on guys. Debugging is *mandatory* for this kind of problem. Papering over it is obscene. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
