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:
> > Will,
> > (+ Cc: Dennis)
> >
> > 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:
> > > > Add memblock_cap_memory_range() which will remove all the memblock regions
> > > > except the range specified in the arguments.
> > > >
> > > > This function, like memblock_mem_limit_remove_map(), will not remove
> > > > memblocks with MEMMAP_NOMAP attribute as they may be mapped and accessed
> > > > later as "device memory."
> > > > See the commit a571d4eb55d8 ("mm/memblock.c: add new infrastructure to
> > > > address the mem limit issue").
> > > >
> > > > This function is used, in a succeeding patch in the series of arm64 kdump
> > > > suuport, to limit the range of usable memory, System RAM, on crash dump
> > > > kernel.
> > > > (Please note that "mem=" parameter is of little use for this purpose.)
> > > >
> > > > Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
> > > > Cc: linux-mm@xxxxxxxxx
> > > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > > > ---
> > > > include/linux/memblock.h | 1 +
> > > > mm/memblock.c | 28 ++++++++++++++++++++++++++++
> > > > 2 files changed, 29 insertions(+)
> > > >
> > > > diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> > > > index 5b759c9..0e770af 100644
> > > > --- a/include/linux/memblock.h
> > > > +++ b/include/linux/memblock.h
> > > > @@ -334,6 +334,7 @@ phys_addr_t memblock_start_of_DRAM(void);
> > > > phys_addr_t memblock_end_of_DRAM(void);
> > > > void memblock_enforce_memory_limit(phys_addr_t memory_limit);
> > > > void memblock_mem_limit_remove_map(phys_addr_t limit);
> > > > +void memblock_cap_memory_range(phys_addr_t base, phys_addr_t size);
> > > > bool memblock_is_memory(phys_addr_t addr);
> > > > int memblock_is_map_memory(phys_addr_t addr);
> > > > int memblock_is_region_memory(phys_addr_t base, phys_addr_t size);
> > > > diff --git a/mm/memblock.c b/mm/memblock.c
> > > > index 7608bc3..eb53876 100644
> > > > --- a/mm/memblock.c
> > > > +++ b/mm/memblock.c
> > > > @@ -1544,6 +1544,34 @@ void __init memblock_mem_limit_remove_map(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);
> > > > +}
> > >
> > > 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.
So I added an extra argument, exact, to a common function to specify
distinct behaviors. Confusing? Please see the patch below.
If nobody objects to this merge, I will submit a whole patchset of kdump
again.
Thanks,
-Takahiro AKASHI
===8<===
include/linux/memblock.h | 1 +
mm/memblock.c | 91 +++++++++++++++++++++++++++++++++++-------------
2 files changed, 68 insertions(+), 24 deletions(-)
diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 5b759c9..0e770af 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -334,6 +334,7 @@ phys_addr_t memblock_start_of_DRAM(void);
phys_addr_t memblock_end_of_DRAM(void);
void memblock_enforce_memory_limit(phys_addr_t memory_limit);
void memblock_mem_limit_remove_map(phys_addr_t limit);
+void memblock_cap_memory_range(phys_addr_t base, phys_addr_t size);
bool memblock_is_memory(phys_addr_t addr);
int memblock_is_map_memory(phys_addr_t addr);
int memblock_is_region_memory(phys_addr_t base, phys_addr_t size);
diff --git a/mm/memblock.c b/mm/memblock.c
index 7608bc3..5f849a9 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1473,9 +1473,10 @@ phys_addr_t __init_memblock memblock_end_of_DRAM(void)
return (memblock.memory.regions[idx].base + memblock.memory.regions[idx].size);
}
-static phys_addr_t __init_memblock __find_max_addr(phys_addr_t limit)
+static phys_addr_t __init_memblock __find_max_addr(phys_addr_t min,
+ phys_addr_t limit)
{
- phys_addr_t max_addr = (phys_addr_t)ULLONG_MAX;
+ phys_addr_t max_addr = (phys_addr_t)ULLONG_MAX, base, size;
struct memblock_region *r;
/*
@@ -1484,11 +1485,22 @@ static phys_addr_t __init_memblock __find_max_addr(phys_addr_t limit)
* of those regions, max_addr will keep original value ULLONG_MAX
*/
for_each_memblock(memory, r) {
- if (limit <= r->size) {
- max_addr = r->base + limit;
+ if (min >= r->base + r->size)
+ continue;
+
+ if (r->base <= min) {
+ base = min;
+ size = r->base + r->size - min;
+ } else {
+ base = r->base;
+ size = r->size;
+ }
+
+ if (limit <= size) {
+ max_addr = base + limit;
break;
}
- limit -= r->size;
+ limit -= size;
}
return max_addr;
@@ -1501,7 +1513,7 @@ void __init memblock_enforce_memory_limit(phys_addr_t limit)
if (!limit)
return;
- max_addr = __find_max_addr(limit);
+ max_addr = __find_max_addr(0, limit);
/* @limit exceeds the total size of the memory, do nothing */
if (max_addr == (phys_addr_t)ULLONG_MAX)
@@ -1514,34 +1526,65 @@ void __init memblock_enforce_memory_limit(phys_addr_t limit)
(phys_addr_t)ULLONG_MAX);
}
-void __init memblock_mem_limit_remove_map(phys_addr_t limit)
+/*
+ * __memblock_cap_memory_range - cap memblock regions
+ * @base: lowest address to clip
+ * @size: size of memory range
+ * @exact: true or false
+ *
+ * If @exact is true, the exact range [@base, @base+@size) of memory with
+ * kernel direct mapping is clipped from memblock.memory. Otherwise, total
+ * of @size of memory is clipped starting from @base.
+ */
+static void __init __memblock_cap_memory_range(phys_addr_t base,
+ phys_addr_t size, bool exact)
{
- struct memblock_type *type = &memblock.memory;
- phys_addr_t max_addr;
- int i, ret, start_rgn, end_rgn;
+ int start_rgn, end_rgn;
+ int i, ret;
- if (!limit)
+ if (!size)
return;
- max_addr = __find_max_addr(limit);
+ if (!exact) {
+ phys_addr_t max_addr;
- /* @limit exceeds the total size of the memory, do nothing */
- if (max_addr == (phys_addr_t)ULLONG_MAX)
- return;
+ max_addr = __find_max_addr(base, size);
+ /* @size exceeds the total size of the memory, do nothing */
+ if (max_addr == (phys_addr_t)ULLONG_MAX)
+ return;
+
+ /* recalc the size to clip the exact range [@base, max_addr) */
+ size = max_addr - base;
+ }
- ret = memblock_isolate_range(type, max_addr, (phys_addr_t)ULLONG_MAX,
- &start_rgn, &end_rgn);
+ ret = memblock_isolate_range(&memblock.memory, base, size,
+ &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);
- }
+ /* remove all the other 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, max_addr,
- (phys_addr_t)ULLONG_MAX);
+ 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)
+{
+ __memblock_cap_memory_range(0, limit, false);
+}
+
+void __init memblock_cap_memory_range(phys_addr_t base, phys_addr_t size)
+{
+ __memblock_cap_memory_range(base, size, true);
}
static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)
--
2.10.0
===>8===
> >
> > Thanks,
> > -Takahiro AKASHI
> >
> > > Will
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