Will,
On Wed, Nov 16, 2016 at 04:30:15PM +0000, Will Deacon wrote:
> Hi Akashi,
>
> On Mon, Nov 14, 2016 at 02:55:16PM +0900, AKASHI Takahiro wrote:
> > On Fri, Nov 11, 2016 at 11:19:04AM +0800, Dennis Chen wrote:
> > > On Fri, Nov 11, 2016 at 11:50:50AM +0900, AKASHI Takahiro wrote:
> > > > On Thu, Nov 10, 2016 at 05:27:20PM +0000, Will Deacon wrote:
> > > > > On Wed, Nov 02, 2016 at 01:51:53PM +0900, AKASHI Takahiro wrote:
> > > > > > +void __init memblock_cap_memory_range(phys_addr_t base, phys_addr_t size)
> > > > > > +{
> > > > > > + int start_rgn, end_rgn;
> > > > > > + int i, ret;
> > > > > > +
> > > > > > + if (!size)
> > > > > > + return;
> > > > > > +
> > > > > > + ret = memblock_isolate_range(&memblock.memory, base, size,
> > > > > > + &start_rgn, &end_rgn);
> > > > > > + if (ret)
> > > > > > + return;
> > > > > > +
> > > > > > + /* remove all the MAP regions */
> > > > > > + for (i = memblock.memory.cnt - 1; i >= end_rgn; i--)
> > > > > > + if (!memblock_is_nomap(&memblock.memory.regions[i]))
> > > > > > + memblock_remove_region(&memblock.memory, i);
> > > > > > +
> > > > > > + for (i = start_rgn - 1; i >= 0; i--)
> > > > > > + if (!memblock_is_nomap(&memblock.memory.regions[i]))
> > > > > > + memblock_remove_region(&memblock.memory, i);
> > > > > > +
> > > > > > + /* truncate the reserved regions */
> > > > > > + memblock_remove_range(&memblock.reserved, 0, base);
> > > > > > + memblock_remove_range(&memblock.reserved,
> > > > > > + base + size, (phys_addr_t)ULLONG_MAX);
> > > > > > +}
> > > > >
> > > > > This duplicates a bunch of the logic in memblock_mem_limit_remove_map. Can
> > > > > you not implement that in terms of your new, more general, function? e.g.
> > > > > by passing base == 0, and size == limit?
> > > >
> > > > Obviously it's possible.
> > > > I actually talked to Dennis before about merging them,
> > > > but he was against my idea.
> > > >
> > > Oops! I thought we have reached agreement in the thread:http://lists.infradead.org/pipermail/linux-arm-kernel/2016-July/442817.html
> > > So feel free to do that as Will'll do
> >
> > OK, but I found that the two functions have a bit different semantics
> > in clipping memory range, in particular, when the range [base,base+size)
> > goes across several regions with a gap.
> > (This does not happen in my arm64 kdump, though.)
> > That is, 'limit' in memblock_mem_limit_remove_map() means total size of
> > available memory, while 'size' in memblock_cap_memory_range() indicates
> > the size of _continuous_ memory range.
>
> I thought limit was just a physical address, and then
No, it's not.
> memblock_mem_limit_remove_map operated on the end of the nearest memblock?
No, but "max_addr" returned by __find_max_addr() is a physical address
and the end address of memory of "limit" size in total.
> You could leave the __find_max_addr call in memblock_mem_limit_remove_map,
> given that I don't think you need/want it for memblock_cap_memory_range.
>
> > So I added an extra argument, exact, to a common function to specify
> > distinct behaviors. Confusing? Please see the patch below.
>
> Oh yikes, this certainly wasn't what I had in mind! My observation was
> just that memblock_mem_limit_remove_map(limit) does:
>
>
> 1. memblock_isolate_range(limit - limit+ULLONG_MAX)
> 2. memblock_remove_region(all non-nomap regions in the isolated region)
> 3. truncate reserved regions to limit
>
> and your memblock_cap_memory_range(base, size) does:
>
> 1. memblock_isolate_range(base - base+size)
> 2, memblock_remove_region(all non-nomap regions above and below the
> isolated region)
> 3. truncate reserved regions around the isolated region
>
> so, assuming we can invert the isolation in one of the cases, then they
> could share the same underlying implementation.
Please see my simplified patch below which would explain what I meant.
(Note that the size is calculated by 'max_addr - 0'.)
> I'm probably just missing something here, because the patch you've ended
> up with is far more involved than I anticipated...
I hope that it will meet almost your anticipation.
Thanks,
-Takahiro AKASHI
>
> Will
===8<===
diff --git a/mm/memblock.c b/mm/memblock.c
index 7608bc3..fea1688 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1514,11 +1514,37 @@ void __init memblock_enforce_memory_limit(phys_addr_t limit)
(phys_addr_t)ULLONG_MAX);
}
+void __init memblock_cap_memory_range(phys_addr_t base, phys_addr_t size)
+{
+ int start_rgn, end_rgn;
+ int i, ret;
+
+ if (!size)
+ return;
+
+ ret = memblock_isolate_range(&memblock.memory, base, size,
+ &start_rgn, &end_rgn);
+ if (ret)
+ return;
+
+ /* remove all the MAP regions */
+ for (i = memblock.memory.cnt - 1; i >= end_rgn; i--)
+ if (!memblock_is_nomap(&memblock.memory.regions[i]))
+ memblock_remove_region(&memblock.memory, i);
+
+ for (i = start_rgn - 1; i >= 0; i--)
+ if (!memblock_is_nomap(&memblock.memory.regions[i]))
+ memblock_remove_region(&memblock.memory, i);
+
+ /* truncate the reserved regions */
+ memblock_remove_range(&memblock.reserved, 0, base);
+ memblock_remove_range(&memblock.reserved,
+ base + size, (phys_addr_t)ULLONG_MAX);
+}
+
void __init memblock_mem_limit_remove_map(phys_addr_t limit)
{
- struct memblock_type *type = &memblock.memory;
phys_addr_t max_addr;
- int i, ret, start_rgn, end_rgn;
if (!limit)
return;
@@ -1529,19 +1555,7 @@ void __init memblock_mem_limit_remove_map(phys_addr_t limit)
if (max_addr == (phys_addr_t)ULLONG_MAX)
return;
- ret = memblock_isolate_range(type, max_addr, (phys_addr_t)ULLONG_MAX,
- &start_rgn, &end_rgn);
- if (ret)
- return;
-
- /* remove all the MAP regions above the limit */
- for (i = end_rgn - 1; i >= start_rgn; i--) {
- if (!memblock_is_nomap(&type->regions[i]))
- memblock_remove_region(type, i);
- }
- /* truncate the reserved regions */
- memblock_remove_range(&memblock.reserved, max_addr,
- (phys_addr_t)ULLONG_MAX);
+ memblock_cap_memory_range(0, max_addr);
}
static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)
--
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