qemus pmemsave doesn't accept "/" in filename

[Muelli]

Binary package hint: qemu-kvm

Please see my conversation with qemu:

(qemu) pmemsave
unexpected end of expression
(qemu) help pmemsave
pmemsave addr size file -- save to disk physical memory dump starting at 'addr' of size 'size'
(qemu) pmemsave 0 512M /tmp/qemu.mem
pmemsave: extraneous characters at the end of line
(qemu) pmemsave 0 512 /tmp/qemu.mem
invalid char in expression
(qemu) pmemsave 0 512 /tmp/qemu
invalid char in expression
(qemu) pmemsave 0 512 qemu.mem
(qemu) pmemsave 0 512M qemu.mem
pmemsave: extraneous characters at the end of line

Let me comment on each one of those:
(qemu) pmemsave
unexpected end of expression

I expected some sort of hint as to where to get more information. Maybe just a "Type ``help pmemsave'' to get syntax information" would be sufficient.

(qemu) help pmemsave
pmemsave addr size file -- save to disk physical memory dump starting at 'addr' of size 'size'

Nice. But an example would be nice. My proposal: "I.e.: pmemsave 0 1G /tmp/qemu.mem"

(qemu) pmemsave 0 512M /tmp/qemu.mem
pmemsave: extraneous characters at the end of line

eh. Would be nice if it told me *which* character was "extraneous" and what "extraneous" means. My proposal: "Couldn't parse character at position 23, please see help pmemsave for an example".

(qemu) pmemsave 0 512 /tmp/qemu.mem
invalid char in expression

Hm. Interesting. Again, would be nice if it printed me the offending character. My proposal: "Could not parse character at position 23, please see help pmemsave for an example".

(qemu) pmemsave 0 512 /tmp/qemu
invalid char in expression

Now I got rid of almost everything but it still doesn't work.

(qemu) pmemsave 0 512 qemu.mem

aha! No slashes?! Seriously?

(qemu) pmemsave 0 512M qemu.mem
pmemsave: extraneous characters at the end of line

And no "M" or "G" modifiers? If I want to dump 2GB then I'd have to calculate the number in bytes and paste that long string. I expected qemu to be able to parse the K, M, G suffixes.

Also, I'm wondering why it doesn't offer to dump all memory.

ProblemType: Bug
Architecture: amd64
CurrentDmesg:
 [150870.676062] kvm_intel: Unknown symbol kvm_vcpu_on_spin
 [150947.222923] cron[24260]: segfault at 0 ip (null) sp 00007fffe865eed8 error 14 in cron[400000+9000]
 [150947.224187] cron[24261]: segfault at 0 ip (null) sp 00007fffe865eed8 error 14 in cron[400000+9000]
Date: Sun Mar 21 15:03:13 2010
DistroRelease: Ubuntu 9.10
KvmCmdLine:
 UID PID PPID C SZ RSS PSR STIME TTY TIME CMD
 muelli 23807 23806 13 239738 228464 0 14:54 pts/8 00:01:22 /usr/bin/kvm -S -M pc -m 512 -smp 1 -name vanilla_ubuntu -monitor stdio -boot c -drive file=/home/muelli/qemu/ubuntu8.10/ubuntu.img,if=ide,index=0,boot=on -drive file=,if=ide,media=cdrom,index=2 -net nic,model=rtl8139,macaddr=f0:00:BA:12:34:56 -net user,hostfwd=tcp::2223-:22,smb=/tmp/share -serial pty -snapshot
MachineType: LENOVO 766636G
Package: kvm 1:84+dfsg-0ubuntu16+0.11.0+0ubuntu6.3
PccardctlIdent:
 Socket 0:
   no product info available
PccardctlStatus:
 Socket 0:
   no card
ProcCmdLine: root=/dev/mapper/cryptroot source=UUID=9c3d5596-27c6-4fd5-bfcd-fa8eef6f1230 ro vdso32=0 quiet splash crashkernel=384M-2G:64M,2G-:128M
ProcVersionSignature: Ubuntu 2.6.32-16.24-generic
SourcePackage: qemu-kvm
Uname: Linux 2.6.32-16-generic x86_64
dmi.bios.date: 03/12/2009
dmi.bios.vendor: LENOVO
dmi.bios.version: 7NETC0WW (2.20 )
dmi.board.name: 766636G
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvr7NETC0WW(2.20):bd03/12/2009:svnLENOVO:pn766636G:pvrThinkPadX61:rvnLENOVO:rn766636G:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 766636G
dmi.product.version: ThinkPad X61
dmi.sys.vendor: LENOVO

[Chuck Short (zulcss)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. Please answer these questions:
1. Is this reproducible?
2. If so, what specific steps should we take to recreate this bug? Be as detailed as possible.
This will help us to find and resolve the problem.

[Muelli (ubuntu-bugs-auftrags-killer)]

1. Yes
2. kvm /tmp/someimage.img -monitor stdio

[Serge Hallyn (serge-hallyn)]

Note that putting quotes around the filename lets you use '/'. I.e.
pmemsave 0x200 0x200 "/tmp/abab"

I assume this is a shortcoming in the parser, as the source code at first glance
claims to simply read a string. So I'm not sure how easily fixable it would be,
but it appears to be something for upstream to consider (whether to fix needing
to quote a filename, or add more precise help on error).

[Anthony Liguori (anthony-codemonkey)]

The '/' character is used to create special expressions if double quotes aren't used.

[Muelli (ubuntu-bugs-auftrags-killer)]

Eh. Well. I'm a bit surprised that you won't allow forward slashes if you try to parse a path. It's actually a quite common character in the Linux world. Even other Unixes use it for separating components of a path. And since people use it so much, it should be as easy as possible to actually give a path to qemu. The excuse that it "is used to create special expressions" (which, btw?!) doesn't hold. I'm pretty confident that people use the '/' character to separate components of a path rather than doing "special expressions". Especially when a path the a file is expected! So if there are still "special expressions" needed in a path, it'd be better to select a different character.

Even if you don't agree on that, I really believe the user deserves some explanation along with the error message that is printed as I've pointed out in comment #0.

[Serge Hallyn (serge-hallyn)]

Muelli: I agree that a help message about quoting pathnames would be
useful. Please work with the upstream mailing list to do so. A small
patch to qemu-monitor.hx should suffice, but you'll need to interact with
the <email address hidden> mailing list.

[Muelli (ubuntu-bugs-auftrags-killer)]

Here's a patch against qemu from git that prints the offending characters, helping the user to understand what's going on.

I can't deal with qemu-devel myself, it's way too noisy. But Ubuntu might want to take that patch or push it upstream.

[Launchpad Janitor (janitor)]

[Expired for qemu-kvm (Ubuntu) because there has been no activity for 60 days.]