Re: [Crash-utility] [PATCH] add support to "virsh dump-guest-memory"(qemu memory dump)
Hello Dave,
I made this patch to make crash can analyze core dump file created by
"virsh dump-guest-memory"(I will call it "qemu memory dump" below).
In
my test(guest OS: RHEL6.2 x86 & x86_64), the patch works well with dump
files created by "qemu memory dump".
However, after some investigation, I think I need to discuss further
works with you.
The core dump created by qemu memory dump is similar to kdump. The
distinctness only focuses on note sections. The former one gets
note sections with a name called "QEMU".
1. Some registers' information stored in "CORE" note sections, needed
by crash, also stores in "QEMU" note sections. I think it's not
reasonable to replace them. What do you think?
2. Other registers which are only stored in "QEMU" note sections are
not directly used in crash. I will continue investigating the use of
these registers. And if you give some suggestion, it will be helpful.
--
--
Regards
Qiao Nuohan
Qiao,
I'm sending this from my home email address -- I am going to be
on vacation for the next two weeks, and will have limited internet
access during that time. So I won't be able to look at this
patch in detail until the week of August 6th.
Anyway, one thing about the patch that I don't like is this
flags/flags2 usage:
#define NETDUMP_DUMPFILE() (pc->flags & (NETDUMP|REM_NETDUMP))
#define DISKDUMP_DUMPFILE() (pc->flags & DISKDUMP)
#define KDUMP_DUMPFILE() (pc->flags & KDUMP)
+#define QEMU_MEM_DUMP_DUMPFILE() ((pc->flags & NETDUMP) && (pc->flags2
&
QEMU_MEM_DUMP))
#define XENDUMP_DUMPFILE() (pc->flags & XENDUMP)
#define XEN_HYPER_MODE() (pc->flags & XEN_HYPER)
None of the other individual dumpfile types "share" a flag with
any other dumpfile type. And so having *both* the NETDUMP flag
*and* the QEMU_MEM_DUMP_DUMPFILE flags set at the same time makes
no sense. It's simply *not* a NETDUMP, and all of the locations
where you do something like this are needlessly confusing:
+ else if (pc->flags & NETDUMP) {
+ if (pc->flags2 & QEMU_MEM_DUMP)
+ retval = qemu_mem_dump_memory_dump(fp);
+ else
+ retval = netdump_memory_dump(fp);
+ }
It may have somehow made your patch easier, but please re-work it
such that QEMU_MEM_DUMP_DUMPFILE() only relies on a single flag bit.
Also, when I get back to work, perhaps you can also make a small sample
dumpfile available to me to test your patch with.
Thanks,
Dave Anderson