From: John Paul Adrian Glaubitz <glaubitz@xxxxxxxxxxxxxxxxxxx> Date: Fri, 24 May 2019 20:51:33 +0200 > On 5/24/19 6:20 PM, David Miller wrote: >>> On the other hand, arm64 currently allows the virtual address size >>> to be configurable, currently defaulting to 48 bits [2, 3]. I was >>> therefore wondering whether we could make MAX_PHYS_ADDRESS_BITS [4] >>> configurable as well to be able to support these JITs on >>> Debian/sparc64 for the foreseeable future by limiting the virtual >>> address space to 47 or 48 bits. >> >> You can't just do this. >> >> It is possible that all physical memory is mapped to the top of the >> mappable physical address range, therefore we really need to use the >> full maximum setting supported by the CPU. > > Yes, my initial mail was incorrect. What I actually meant was reducing > the size of the va_hole in userspace so that the top-most address that > mmap() would return is not beyond 2^47. > > Would it be possible to add such a workaround until the JITs have fixed > their broken code? I suppose that's doable, sure.
