linux.git/mm/sparse.c, branch v6.1.168

x86/kaslr: Expose and use the end of the physical memory address space

2024-09-12T09:10:17+00:00

commit ea72ce5da22806d5713f3ffb39a6d5ae73841f93 upstream.

iounmap() on x86 occasionally fails to unmap because the provided valid
ioremap address is not below high_memory. It turned out that this
happens due to KASLR.

KASLR uses the full address space between PAGE_OFFSET and vaddr_end to
randomize the starting points of the direct map, vmalloc and vmemmap
regions.  It thereby limits the size of the direct map by using the
installed memory size plus an extra configurable margin for hot-plug
memory.  This limitation is done to gain more randomization space
because otherwise only the holes between the direct map, vmalloc,
vmemmap and vaddr_end would be usable for randomizing.

The limited direct map size is not exposed to the rest of the kernel, so
the memory hot-plug and resource management related code paths still
operate under the assumption that the available address space can be
determined with MAX_PHYSMEM_BITS.

request_free_mem_region() allocates from (1 << MAX_PHYSMEM_BITS) - 1
downwards.  That means the first allocation happens past the end of the
direct map and if unlucky this address is in the vmalloc space, which
causes high_memory to become greater than VMALLOC_START and consequently
causes iounmap() to fail for valid ioremap addresses.

MAX_PHYSMEM_BITS cannot be changed for that because the randomization
does not align with address bit boundaries and there are other places
which actually require to know the maximum number of address bits.  All
remaining usage sites of MAX_PHYSMEM_BITS have been analyzed and found
to be correct.

Cure this by exposing the end of the direct map via PHYSMEM_END and use
that for the memory hot-plug and resource management related places
instead of relying on MAX_PHYSMEM_BITS. In the KASLR case PHYSMEM_END
maps to a variable which is initialized by the KASLR initialization and
otherwise it is based on MAX_PHYSMEM_BITS as before.

To prevent future hickups add a check into add_pages() to catch callers
trying to add memory above PHYSMEM_END.

Fixes: 0483e1fa6e09 ("x86/mm: Implement ASLR for kernel memory regions")
Reported-by: Max Ramanouski 
Reported-by: Alistair Popple 
Signed-off-by: Thomas Gleixner 
Tested-By: Max Ramanouski 
Tested-by: Alistair Popple 
Reviewed-by: Dan Williams 
Reviewed-by: Alistair Popple 
Reviewed-by: Kees Cook 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/87ed6soy3z.ffs@tglx
Signed-off-by: Greg Kroah-Hartman

mm/sparsemem: fix race in accessing memory_section->usage

2024-02-01T00:17:02+00:00

commit 5ec8e8ea8b7783fab150cf86404fc38cb4db8800 upstream.

The below race is observed on a PFN which falls into the device memory
region with the system memory configuration where PFN's are such that
[ZONE_NORMAL ZONE_DEVICE ZONE_NORMAL].  Since normal zone start and end
pfn contains the device memory PFN's as well, the compaction triggered
will try on the device memory PFN's too though they end up in NOP(because
pfn_to_online_page() returns NULL for ZONE_DEVICE memory sections).  When
from other core, the section mappings are being removed for the
ZONE_DEVICE region, that the PFN in question belongs to, on which
compaction is currently being operated is resulting into the kernel crash
with CONFIG_SPASEMEM_VMEMAP enabled.  The crash logs can be seen at [1].

compact_zone()			memunmap_pages
-------------			---------------
__pageblock_pfn_to_page
   ......
 (a)pfn_valid():
     valid_section()//return true
			      (b)__remove_pages()->
				  sparse_remove_section()->
				    section_deactivate():
				    [Free the array ms->usage and set
				     ms->usage = NULL]
     pfn_section_valid()
     [Access ms->usage which
     is NULL]

NOTE: From the above it can be said that the race is reduced to between
the pfn_valid()/pfn_section_valid() and the section deactivate with
SPASEMEM_VMEMAP enabled.

The commit b943f045a9af("mm/sparse: fix kernel crash with
pfn_section_valid check") tried to address the same problem by clearing
the SECTION_HAS_MEM_MAP with the expectation of valid_section() returns
false thus ms->usage is not accessed.

Fix this issue by the below steps:

a) Clear SECTION_HAS_MEM_MAP before freeing the ->usage.

b) RCU protected read side critical section will either return NULL
   when SECTION_HAS_MEM_MAP is cleared or can successfully access ->usage.

c) Free the ->usage with kfree_rcu() and set ms->usage = NULL.  No
   attempt will be made to access ->usage after this as the
   SECTION_HAS_MEM_MAP is cleared thus valid_section() return false.

Thanks to David/Pavan for their inputs on this patch.

[1] https://lore.kernel.org/linux-mm/994410bb-89aa-d987-1f50-f514903c55aa@quicinc.com/

On Snapdragon SoC, with the mentioned memory configuration of PFN's as
[ZONE_NORMAL ZONE_DEVICE ZONE_NORMAL], we are able to see bunch of
issues daily while testing on a device farm.

For this particular issue below is the log.  Though the below log is
not directly pointing to the pfn_section_valid(){ ms->usage;}, when we
loaded this dump on T32 lauterbach tool, it is pointing.

[  540.578056] Unable to handle kernel NULL pointer dereference at
virtual address 0000000000000000
[  540.578068] Mem abort info:
[  540.578070]   ESR = 0x0000000096000005
[  540.578073]   EC = 0x25: DABT (current EL), IL = 32 bits
[  540.578077]   SET = 0, FnV = 0
[  540.578080]   EA = 0, S1PTW = 0
[  540.578082]   FSC = 0x05: level 1 translation fault
[  540.578085] Data abort info:
[  540.578086]   ISV = 0, ISS = 0x00000005
[  540.578088]   CM = 0, WnR = 0
[  540.579431] pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBSBTYPE=--)
[  540.579436] pc : __pageblock_pfn_to_page+0x6c/0x14c
[  540.579454] lr : compact_zone+0x994/0x1058
[  540.579460] sp : ffffffc03579b510
[  540.579463] x29: ffffffc03579b510 x28: 0000000000235800 x27:000000000000000c
[  540.579470] x26: 0000000000235c00 x25: 0000000000000068 x24:ffffffc03579b640
[  540.579477] x23: 0000000000000001 x22: ffffffc03579b660 x21:0000000000000000
[  540.579483] x20: 0000000000235bff x19: ffffffdebf7e3940 x18:ffffffdebf66d140
[  540.579489] x17: 00000000739ba063 x16: 00000000739ba063 x15:00000000009f4bff
[  540.579495] x14: 0000008000000000 x13: 0000000000000000 x12:0000000000000001
[  540.579501] x11: 0000000000000000 x10: 0000000000000000 x9 :ffffff897d2cd440
[  540.579507] x8 : 0000000000000000 x7 : 0000000000000000 x6 :ffffffc03579b5b4
[  540.579512] x5 : 0000000000027f25 x4 : ffffffc03579b5b8 x3 :0000000000000001
[  540.579518] x2 : ffffffdebf7e3940 x1 : 0000000000235c00 x0 :0000000000235800
[  540.579524] Call trace:
[  540.579527]  __pageblock_pfn_to_page+0x6c/0x14c
[  540.579533]  compact_zone+0x994/0x1058
[  540.579536]  try_to_compact_pages+0x128/0x378
[  540.579540]  __alloc_pages_direct_compact+0x80/0x2b0
[  540.579544]  __alloc_pages_slowpath+0x5c0/0xe10
[  540.579547]  __alloc_pages+0x250/0x2d0
[  540.579550]  __iommu_dma_alloc_noncontiguous+0x13c/0x3fc
[  540.579561]  iommu_dma_alloc+0xa0/0x320
[  540.579565]  dma_alloc_attrs+0xd4/0x108

[quic_charante@quicinc.com: use kfree_rcu() in place of synchronize_rcu(), per David]
  Link: https://lkml.kernel.org/r/1698403778-20938-1-git-send-email-quic_charante@quicinc.com
Link: https://lkml.kernel.org/r/1697202267-23600-1-git-send-email-quic_charante@quicinc.com
Fixes: f46edbd1b151 ("mm/sparsemem: add helpers track active portions of a section at boot")
Signed-off-by: Charan Teja Kalla 
Cc: Aneesh Kumar K.V 
Cc: Dan Williams 
Cc: David Hildenbrand 
Cc: Mel Gorman 
Cc: Oscar Salvador 
Cc: Vlastimil Babka 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

mm: memory_hotplug: enumerate all supported section flags

2022-07-04T01:08:49+00:00

Patch series "make hugetlb_optimize_vmemmap compatible with
memmap_on_memory", v3.

This series makes hugetlb_optimize_vmemmap compatible with
memmap_on_memory.


This patch (of 2):

We are almost running out of section flags, only one bit is available in
the worst case (powerpc with 256k pages).  However, there are still some
free bits (in ->section_mem_map) on other architectures (e.g.  x86_64 has
10 bits available, arm64 has 8 bits available with worst case of 64K
pages).  We have hard coded those numbers in code, it is inconvenient to
use those bits on other architectures except powerpc.  So transfer those
section flags to enumeration to make it easy to add new section flags in
the future.  Also, move SECTION_TAINT_ZONE_DEVICE into the scope of
CONFIG_ZONE_DEVICE to save a bit on non-zone-device case.

[songmuchun@bytedance.com: replace enum with defines per David]
  Link: https://lkml.kernel.org/r/20220620110616.12056-2-songmuchun@bytedance.com
Link: https://lkml.kernel.org/r/20220617135650.74901-1-songmuchun@bytedance.com
Link: https://lkml.kernel.org/r/20220617135650.74901-2-songmuchun@bytedance.com
Signed-off-by: Muchun Song 
Reviewed-by: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Mike Kravetz 
Cc: Oscar Salvador 
Cc: Paul E. McKenney 
Cc: Xiongchun Duan 
Signed-off-by: Andrew Morton

mm/memory-failure.c: move clear_hwpoisoned_pages

2022-05-13T14:20:19+00:00

Patch series "memory-failure: fix hwpoison_filter", v2.

As well known, the memory failure mechanism handles memory corrupted
event, and try to send SIGBUS to the user process which uses this
corrupted page.

For the virtualization case, QEMU catches SIGBUS and tries to inject MCE
into the guest, and the guest handles memory failure again.  Thus the
guest gets the minimal effect from hardware memory corruption.

The further step I'm working on:

1, try to modify code to decrease poisoned pages in a single place
   (mm/memofy-failure.c: simplify num_poisoned_pages_dec in this series).

2, try to use page_handle_poison() to handle SetPageHWPoison() and
   num_poisoned_pages_inc() together.  It would be best to call
   num_poisoned_pages_inc() in a single place too.

3, introduce memory failure notifier list in memory-failure.c: notify
   the corrupted PFN to someone who registers this list.  If I can
   complete [1] and [2] part, [3] will be quite easy(just call notifier
   list after increasing poisoned page).

4, introduce memory recover VQ for memory balloon device, and registers
   memory failure notifier list.  During the guest kernel handles memory
   failure, balloon device gets notified by memory failure notifier list,
   and tells the host to recover the corrupted PFN(GPA) by the new VQ.

5, host side remaps the corrupted page(HVA), and tells the guest side
   to unpoison the PFN(GPA).  Then the guest fixes the corrupted page(GPA)
   dynamically.


This patch (of 5):

clear_hwpoisoned_pages() clears HWPoison flag and decreases the number of
poisoned pages, this actually works as part of memory failure.

Move this function from sparse.c to memory-failure.c, finally there is no
CONFIG_MEMORY_FAILURE in sparse.c.

Link: https://lkml.kernel.org/r/20220509105641.491313-1-pizhenwei@bytedance.com
Link: https://lkml.kernel.org/r/20220509105641.491313-2-pizhenwei@bytedance.com
Signed-off-by: zhenwei pi 
Acked-by: Naoya Horiguchi 
Signed-off-by: Andrew Morton

mm/sparse-vmemmap: add a pgmap argument to section activation

2022-04-29T06:16:15+00:00

Patch series "sparse-vmemmap: memory savings for compound devmaps (device-dax)", v9.

This series minimizes 'struct page' overhead by pursuing a similar
approach as Muchun Song series "Free some vmemmap pages of hugetlb page"
(now merged since v5.14), but applied to devmap with @vmemmap_shift
(device-dax).  

The vmemmap dedpulication original idea (already used in HugeTLB) is to
reuse/deduplicate tail page vmemmap areas, particular the area which only
describes tail pages.  So a vmemmap page describes 64 struct pages, and
the first page for a given ZONE_DEVICE vmemmap would contain the head page
and 63 tail pages.  The second vmemmap page would contain only tail pages,
and that's what gets reused across the rest of the subsection/section. 
The bigger the page size, the bigger the savings (2M hpage -> save 6
vmemmap pages; 1G hpage -> save 4094 vmemmap pages).  

This is done for PMEM /specifically only/ on device-dax configured
namespaces, not fsdax.  In other words, a devmap with a @vmemmap_shift.

In terms of savings, per 1Tb of memory, the struct page cost would go down
with compound devmap:

* with 2M pages we lose 4G instead of 16G (0.39% instead of 1.5% of
  total memory)

* with 1G pages we lose 40MB instead of 16G (0.0014% instead of 1.5% of
  total memory)

The series is mostly summed up by patch 4, and to summarize what the
series does:

Patches 1 - 3: Minor cleanups in preparation for patch 4.  Move the very
nice docs of hugetlb_vmemmap.c into a Documentation/vm/ entry.

Patch 4: Patch 4 is the one that takes care of the struct page savings
(also referred to here as tail-page/vmemmap deduplication).  Much like
Muchun series, we reuse the second PTE tail page vmemmap areas across a
given @vmemmap_shift On important difference though, is that contrary to
the hugetlbfs series, there's no vmemmap for the area because we are
late-populating it as opposed to remapping a system-ram range.  IOW no
freeing of pages of already initialized vmemmap like the case for
hugetlbfs, which greatly simplifies the logic (besides not being
arch-specific).  altmap case unchanged and still goes via the
vmemmap_populate().  Also adjust the newly added docs to the device-dax
case.

[Note that device-dax is still a little behind HugeTLB in terms of
savings.  I have an additional simple patch that reuses the head vmemmap
page too, as a follow-up.  That will double the savings and namespaces
initialization.]

Patch 5: Initialize fewer struct pages depending on the page size with
DRAM backed struct pages -- because fewer pages are unique and most tail
pages (with bigger vmemmap_shift).

    NVDIMM namespace bootstrap improves from ~268-358 ms to
    ~80-110/<1ms on 128G NVDIMMs with 2M and 1G respectivally.  And struct
    page needed capacity will be 3.8x / 1071x smaller for 2M and 1G
    respectivelly.  Tested on x86 with 1.5Tb of pmem (including pinning,
    and RDMA registration/deregistration scalability with 2M MRs)


This patch (of 5):

In support of using compound pages for devmap mappings, plumb the pgmap
down to the vmemmap_populate implementation.  Note that while altmap is
retrievable from pgmap the memory hotplug code passes altmap without
pgmap[*], so both need to be independently plumbed.

So in addition to @altmap, pass @pgmap to sparse section populate
functions namely:

	sparse_add_section
	  section_activate
	    populate_section_memmap
   	      __populate_section_memmap

Passing @pgmap allows __populate_section_memmap() to both fetch the
vmemmap_shift in which memmap metadata is created for and also to let
sparse-vmemmap fetch pgmap ranges to co-relate to a given section and pick
whether to just reuse tail pages from past onlined sections.

While at it, fix the kdoc for @altmap for sparse_add_section().

[*] https://lore.kernel.org/linux-mm/20210319092635.6214-1-osalvador@suse.de/

Link: https://lkml.kernel.org/r/20220420155310.9712-1-joao.m.martins@oracle.com
Link: https://lkml.kernel.org/r/20220420155310.9712-2-joao.m.martins@oracle.com
Signed-off-by: Joao Martins 
Reviewed-by: Dan Williams 
Reviewed-by: Muchun Song 
Cc: Vishal Verma 
Cc: Matthew Wilcox 
Cc: Jason Gunthorpe 
Cc: Jane Chu 
Cc: Mike Kravetz 
Cc: Jonathan Corbet 
Cc: Christoph Hellwig 
Signed-off-by: Andrew Morton

mm/sparse: make mminit_validate_memmodel_limits() static

2022-03-22T22:57:05+00:00

It's only used in the sparse.c now. So we can make it static and further
clean up the relevant code.

Link: https://lkml.kernel.org/r/20220127093221.63524-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin 
Reviewed-by: Mike Rapoport 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bootmem: Use page->index instead of page->freelist

2022-01-06T11:27:03+00:00

page->freelist is for the use of slab.  Using page->index is the same
set of bits as page->freelist, and by using an integer instead of a
pointer, we can avoid casts.

Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Vlastimil Babka 
Acked-by: Johannes Weiner 
Cc: Dave Hansen 
Cc: Andy Lutomirski 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Borislav Petkov 
Cc: 
Cc: "H. Peter Anvin"

memblock: use memblock_free for freeing virtual pointers

2021-11-06T20:30:41+00:00

Rename memblock_free_ptr() to memblock_free() and use memblock_free()
when freeing a virtual pointer so that memblock_free() will be a
counterpart of memblock_alloc()

The callers are updated with the below semantic patch and manual
addition of (void *) casting to pointers that are represented by
unsigned long variables.

    @@
    identifier vaddr;
    expression size;
    @@
    (
    - memblock_phys_free(__pa(vaddr), size);
    + memblock_free(vaddr, size);
    |
    - memblock_free_ptr(vaddr, size);
    + memblock_free(vaddr, size);
    )

[sfr@canb.auug.org.au: fixup]
  Link: https://lkml.kernel.org/r/20211018192940.3d1d532f@canb.auug.org.au

Link: https://lkml.kernel.org/r/20210930185031.18648-7-rppt@kernel.org
Signed-off-by: Mike Rapoport 
Signed-off-by: Stephen Rothwell 
Cc: Christophe Leroy 
Cc: Juergen Gross 
Cc: Shahab Vahedi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memblock: rename memblock_free to memblock_phys_free

2021-11-06T20:30:41+00:00

Since memblock_free() operates on a physical range, make its name
reflect it and rename it to memblock_phys_free(), so it will be a
logical counterpart to memblock_phys_alloc().

The callers are updated with the below semantic patch:

    @@
    expression addr;
    expression size;
    @@
    - memblock_free(addr, size);
    + memblock_phys_free(addr, size);

Link: https://lkml.kernel.org/r/20210930185031.18648-6-rppt@kernel.org
Signed-off-by: Mike Rapoport 
Cc: Christophe Leroy 
Cc: Juergen Gross 
Cc: Shahab Vahedi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memblock: drop memblock_free_early_nid() and memblock_free_early()

2021-11-06T20:30:41+00:00

memblock_free_early_nid() is unused and memblock_free_early() is an
alias for memblock_free().

Replace calls to memblock_free_early() with calls to memblock_free() and
remove memblock_free_early() and memblock_free_early_nid().

Link: https://lkml.kernel.org/r/20210930185031.18648-4-rppt@kernel.org
Signed-off-by: Mike Rapoport 
Cc: Christophe Leroy 
Cc: Juergen Gross 
Cc: Shahab Vahedi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds