[PATCH] arm64: move back to generic memblock_enforce_memory_limit()

[Catalin Marinas]

On Tue, Feb 02, 2016 at 11:28:41AM +0100, Ard Biesheuvel wrote:
> On 2 February 2016 at 11:19, Catalin Marinas <catalin.marinas at arm.com> wrote:
> > On Mon, Feb 01, 2016 at 07:30:17PM +0100, Ard Biesheuvel wrote:
> >>  void __init arm64_memblock_init(void)
> >>  {
> >>       const s64 linear_region_size = -(s64)PAGE_OFFSET;
> >> @@ -215,24 +180,14 @@ void __init arm64_memblock_init(void)
> >>       if (memblock_end_of_DRAM() > linear_region_size)
> >>               memblock_remove(0, memblock_end_of_DRAM() - linear_region_size);
> >>
> >> +     /*
> >> +      * Apply the memory limit if it was set. Since the kernel may be loaded
> >> +      * high up in memory, add back the kernel region that must be accessible
> >> +      * via the linear mapping.
> >> +      */
> >>       if (memory_limit != (phys_addr_t)ULLONG_MAX) {
> >> -             u64 kbase = round_down(__pa(_text), MIN_KIMG_ALIGN);
> >> -             u64 kend = PAGE_ALIGN(__pa(_end));
> >> -             u64 const sz_4g = 0x100000000UL;
> >> -
> >> -             /*
> >> -              * Clip memory in order of preference:
> >> -              * - above the kernel and above 4 GB
> >> -              * - between 4 GB and the start of the kernel (if the kernel
> >> -              *   is loaded high in memory)
> >> -              * - between the kernel and 4 GB (if the kernel is loaded
> >> -              *   low in memory)
> >> -              * - below 4 GB
> >> -              */
> >> -             clip_mem_range(max(sz_4g, kend), ULLONG_MAX);
> >> -             clip_mem_range(sz_4g, kbase);
> >> -             clip_mem_range(kend, sz_4g);
> >> -             clip_mem_range(0, min(kbase, sz_4g));
> >> +             memblock_enforce_memory_limit(memory_limit);
> >> +             memblock_add(__pa(__init_begin), (u64)(_end - __init_begin));
> >
> > Thanks, it looks much simpler now. However, loading the kernel 1GB
> > higher with mem=1G fails somewhere during the KVM hyp initialisation. It
> > works if I change the last line below to:
> >
> >         memblock_add(__pa(_text), (u64)(_end - _text));
> 
> OK, that should work as well.
> 
> I suppose the fact that mem= loses some of its accuracy is not an
> issue? If you need it to be exact, you should simply not load your
> kernel outside your mem= range ...

I'm not worried about accuracy. We could avoid freeing the init mem if
the kernel is outside the memory_limit range but I don't really think
it's worth.

-- 
Catalin