[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH 09/14] livepatch: Add per-function applied/reverted state tracking marker

Hi Pawel,

On 22/08/2019 12:02, Wieczorkiewicz, Pawel wrote:
On 22. Aug 2019, at 12:29, Julien Grall <julien.grall@xxxxxxx <mailto:julien.grall@xxxxxxx>> wrote:
On 21/08/2019 09:19, Pawel Wieczorkiewicz wrote:
More generally, I am not very comfortable to see panic() in the middle of the code. Could you explain why panic is the best solution over reverting the work?

Yes. Production-ready hotpatches must not contain inconsistent hooks or functions-to-be-applied/reverted. The goal here is to detect such hotpatches and fail hard immediately highlighting the fact that such hotpatch
is broken.

Aside the len = 0 that you are going to fix. How would this condition happen? Are you going to add code that will potentially trigger the panic?

The inconsistent application of a hotpatch (some function applied, some reverted while other left behined) leaves the system in a very bad state. I think the best what we could do here is panic() to enable post-mortem analysis
of what went wrong and avoid leaking such system into production.

Thank you for the explanation here (and on IRC). May I ask some documentation regarding the panic in at least commit message? Ideally, this would explain why the panic the most sensible solution.


Julien Grall

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.