From: Ian Jackson <iwj@xenproject.org>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Xen-devel <xen-devel@lists.xenproject.org>,
"Michał Leszczyński" <michal.leszczynski@cert.pl>,
"Wei Liu" <wl@xen.org>, "Tamas K Lengyel" <tamas@tklengyel.com>
Subject: Re: [PATCH v7 08/10] tools/misc: Add xen-vmtrace tool
Date: Tue, 26 Jan 2021 13:32:43 +0000 [thread overview]
Message-ID: <24592.6651.498517.334163@mariner.uk.xensource.com> (raw)
In-Reply-To: <445bd883-3900-6a28-10e9-84251af43123@citrix.com>
Andrew Cooper writes ("Re: [PATCH v7 08/10] tools/misc: Add xen-vmtrace tool"):
> On 26/01/2021 11:59, Ian Jackson wrote:
> >[Andrew:]
> >> This is example code, not a production utility.
> > Perhaps the utility could print some kind of health warning about it
> > possibly leaving this perf-impacting feature enabled, and how to clean
> > up ?
>
> Why? The theoretical fallout here is not conceptually different to
> libxl or qemu segfaulting, or any of the myriad other random utilities
> we have.
>
> Printing "Warning - this program, just like everything else in the Xen
> tree, might in exceptional circumstances segfault and leave the domain
> in a weird state" is obvious, and doesn't need stating.
>
> The domain is stuffed. `xl destroy` may or may not make the problem go away.
Firstly, I don't agree with this pessimistic analysis of our current
tooling. Secondly, I would consider many such behaviours bugs;
certainly we have bugs but we shouldn't introduce more of them.
You are justifying the poor robustness of this tool on the grounds
that it's "example code, not a production utility".
But we are shipping it to bin/ and there is nothing telling anyone
that trying to use it (perhaps wrapped in something of their own
devising) is a bad idea.
Either this is code users might be expected to run in production in
which we need to make it at least have a minimal level of engineering
robustness (which is perhaps too difficult at this stage), or we need
to communicate to our users that it's a programming example, not a
useful utility.
Note that *even if it is a programming example*, we should highlight
its most important deficiencies. Otherwise it is a hazardously
misleading example.
I hope that makes sense.
Thanks,
Ian.
next prev parent reply other threads:[~2021-01-26 13:33 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-21 21:27 [PATCH v7 00/10] Implement support for external IPT monitoring Andrew Cooper
2021-01-21 21:27 ` [PATCH v7 01/10] xen+tools: Introduce XEN_SYSCTL_PHYSCAP_vmtrace Andrew Cooper
2021-01-22 15:28 ` Ian Jackson
2021-01-26 8:58 ` Julien Grall
2021-01-26 10:04 ` Andrew Cooper
2021-01-21 21:27 ` [PATCH v7 02/10] xen/domain: Add vmtrace_frames domain creation parameter Andrew Cooper
2021-01-25 15:08 ` Jan Beulich
2021-01-25 17:17 ` Andrew Cooper
2021-01-26 10:51 ` Jan Beulich
2021-01-29 16:37 ` Jan Beulich
2021-01-21 21:27 ` [PATCH v7 03/10] tools/[lib]xl: Add vmtrace_buf_size parameter Andrew Cooper
2021-01-22 15:29 ` Ian Jackson
2021-01-21 21:27 ` [PATCH v7 04/10] xen/memory: Add a vmtrace_buf resource type Andrew Cooper
2021-01-25 16:31 ` Jan Beulich
2021-01-26 7:37 ` Jan Beulich
2021-01-26 9:58 ` Andrew Cooper
2021-01-26 10:30 ` Jan Beulich
2021-01-21 21:27 ` [PATCH v7 05/10] x86/vmx: Add Intel Processor Trace support Andrew Cooper
2021-01-26 13:35 ` Jan Beulich
2021-01-29 22:08 ` Andrew Cooper
2021-01-21 21:27 ` [PATCH v7 06/10] xen/domctl: Add XEN_DOMCTL_vmtrace_op Andrew Cooper
2021-01-26 14:18 ` Jan Beulich
2021-01-29 23:01 ` Andrew Cooper
2021-01-21 21:27 ` [PATCH v7 07/10] tools/libxc: Add xc_vmtrace_* functions Andrew Cooper
2021-01-22 15:29 ` Ian Jackson
2021-01-21 21:27 ` [PATCH v7 08/10] tools/misc: Add xen-vmtrace tool Andrew Cooper
2021-01-22 15:33 ` Ian Jackson
2021-01-25 15:30 ` Andrew Cooper
2021-01-26 11:59 ` Ian Jackson
2021-01-26 12:55 ` Andrew Cooper
2021-01-26 13:32 ` Ian Jackson [this message]
2021-01-26 15:59 ` Andrew Cooper
2021-01-21 21:27 ` [PATCH v7 09/10] xen/vmtrace: support for VM forks Andrew Cooper
2021-01-26 14:21 ` Jan Beulich
2021-01-27 15:50 ` Lengyel, Tamas
2021-01-21 21:27 ` [PATCH v7 10/10] x86/vm_event: Carry Processor Trace buffer offset in vm_event Andrew Cooper
2021-01-26 14:27 ` Jan Beulich
2021-01-29 23:22 ` Andrew Cooper
2021-01-29 23:40 ` Tamas K Lengyel
2021-02-01 8:55 ` Jan Beulich
2021-02-01 9:06 ` Andrew Cooper
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