v2->v3 [Paolo]:
- The memory API guarantees an increasing traversal. Drop the hash
tables and build the final list directly in the region_add callback,
merging any adjacent region only with the last element on the list.
(Patch #3.)
When dumping a 3700 MB guest, the following messages were logged by
the debug fprintf() (which is disabled by default):
guest_phys_blocks_region_add: target_start=0000000000000000
target_end=00000000000a0000: added (count: 1)
guest_phys_blocks_region_add: target_start=00000000000c0000
target_end=00000000000ca000: added (count: 2)
guest_phys_blocks_region_add: target_start=00000000000ca000
target_end=00000000000cd000: joined (count: 2)
guest_phys_blocks_region_add: target_start=00000000000cd000
target_end=00000000000d0000: joined (count: 2)
guest_phys_blocks_region_add: target_start=00000000000d0000
target_end=00000000000f0000: joined (count: 2)
guest_phys_blocks_region_add: target_start=00000000000f0000
target_end=0000000000100000: joined (count: 2)
guest_phys_blocks_region_add: target_start=0000000000100000
target_end=00000000e0000000: joined (count: 2)
guest_phys_blocks_region_add: target_start=00000000fc000000
target_end=00000000fc800000: added (count: 3)
guest_phys_blocks_region_add: target_start=00000000fffe0000
target_end=0000000100000000: added (count: 4)
guest_phys_blocks_region_add: target_start=0000000100000000
target_end=0000000107400000: added (count: 5)
The vmcore (verified with "crash") had the following PT_LOAD entries:
Offset VirtAddr PhysAddr FileSiz MemSiz
---------- ------------------ ------------------ ---------- ----------
0x0004b8 0x0000000000000000 0x0000000000000000 0x0a0000 0x0a0000
0x0a04b8 0x0000000000000000 0x00000000000c0000 0xdff40000 0xdff40000
0xdffe04b8 0x0000000000000000 0x00000000fc000000 0x800000 0x800000
0xe07e04b8 0x0000000000000000 0x00000000fffe0000 0x020000 0x020000
0xe08004b8 0x0000000000000000 0x0000000100000000 0x7400000 0x7400000
v1->v2 [Luiz]:
- fix up the cpu_get_dump_info() prototype in "target-s390x/arch_dump.c"
that has been introduced between my posting of v1 and Luiz's applying
it to qmp-1.6. (Patch #4.)
v1 blurb:
Conceptually, the dump-guest-memory command works as follows:
(a) pause the guest,
(b) get a snapshot of the guest's physical memory map, as provided by
qemu,
(c) retrieve the guest's virtual mappings, as seen by the guest (this is
where paging=true vs. paging=false makes a difference),
(d) filter (c) as requested by the QMP caller,
(e) write ELF headers, keying off (b) -- the guest's physmap -- and (d)
-- the filtered guest mappings.
(f) dump RAM contents, keying off the same (b) and (d),
(g) unpause the guest (if necessary).
Patch #1 affects step (e); specifically, how (d) is matched against (b),
when "paging" is "true", and the guest kernel maps more guest-physical
RAM than it actually has.
This can be done by non-malicious, clean-state guests (eg. a pristine
RHEL-6.4 guest), and may cause libbfd errors due to PT_LOAD entries
(coming directly from the guest page tables) exceeding the vmcore file's
size.
Patches #2 to #4 are independent of the "paging" option (or, more
precisely, affect them equally); they affect (b). Currently input
parameter (b), that is, the guest's physical memory map as provided by
qemu, is implicitly represented by "ram_list.blocks". As a result, steps
and outputs dependent on (b) will refer to qemu-internal offsets.
Unfortunately, this breaks when the guest-visible physical addresses
diverge from the qemu-internal, RAMBlock based representation. This can
happen eg. for guests > 3.5 GB, due to the 32-bit PCI hole; see patch #4
for a diagram.
Patch #2 introduces input parameter (b) explicitly, as a reasonably
minimal map of guest-physical address ranges. (Minimality is not a hard
requirement here, it just decreases the number of PT_LOAD entries
written to the vmcore header.) Patch #3 populates this map. Patch #4
rebases the dump-guest-memory command to it, so that steps (e) and (f)
work with guest-phys addresses.
As a result, the "crash" utility can parse vmcores dumped for big x86_64
guests (paging=false).
Please refer to Red Hat Bugzilla 981582
<https://bugzilla.redhat.com/show_bug.cgi?id=981582>.
Laszlo Ersek (4):
dump: clamp guest-provided mapping lengths to ramblock sizes
dump: introduce GuestPhysBlockList
dump: populate guest_phys_blocks
dump: rebase from host-private RAMBlock offsets to guest-physical
addresses
include/sysemu/dump.h | 4 +-
include/sysemu/memory_mapping.h | 30 +++++++-
dump.c | 171 ++++++++++++++++++++++-----------------
memory_mapping.c | 123 ++++++++++++++++++++++++++--
stubs/dump.c | 3 +-
target-i386/arch_dump.c | 10 ++-
target-s390x/arch_dump.c | 3 +-
7 files changed, 251 insertions(+), 93 deletions(-)
