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Re: [Xen-devel] [PATCH 0/3] xen/arm: Inject an exception to the guest rather than crashing it

On 30/01/18 16:38, Andrew Cooper wrote:
On 30/01/18 16:14, Julien Grall wrote:
Hi all,

This small series replaces all call to domain_crash_synchronous by injecting
an exception to the guest.

This will result to a nicer trace from the guest (no need to manually walk
the stack) and give a chance to the guest to give a bit more information on
what it was doing.


Julien Grall (3):
   xen/arm: io: Distinguish unhandled IO from aborted one
   xen/arm: Don't crash domain on bad MMIO emulation
   xen/arm: Don't crash the domain on invalid HVC immediate


I don't feel qualified to review these, but some notes.

Patch 1.  s/avodi/avoid/ in the commit message

Patches 2 and 3.  You probably want to convert the printks to
gdprintk()s, otherwise guests can choke up the ratelimited log.  Doing
so will also mean that the vcpu will be identified consistently, which
it isn't currently.
We didn't use g*printk because it would be more confusing to print the current vCPU in some cases (e.g when accessing the re-distributor of another vCPU) or does not matter (e.g for ITS).

The problem with the debug version is those information are actually quite useful in non-debug build. We found quite a few issues thanks to them.

I think it would make more sense for Xen to provide per-guest ratelimited than hiding those messages in non-debug build.


Julien Grall

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