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From: Markus Armbruster <armbru@redhat.com>
References: <20180524044454.11792-1-peterx@redhat.com>
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Date: Thu, 14 Jun 2018 14:51:30 +0200
In-Reply-To: <dfb61dcd-c180-1307-bf9d-086aa15478ec@redhat.com> (Auger Eric's
	message of "Wed, 13 Jun 2018 11:36:05 +0200")
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Subject: Re: [Qemu-devel] [PATCH v4 2/2] intel-iommu: start to use
 error_report_once
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To: Auger Eric <eric.auger@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>, Peter Xu <peterx@redhat.com>, Jason Wang <jasowang@redhat.com>, "Michael S . Tsirkin" <mst@redhat.com>, Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= <f4bug@amsat.org>, qemu-devel@nongnu.org, Peter Maydell <peter.maydell@linaro.org>

Auger Eric <eric.auger@redhat.com> writes:

> Hi,
> On 06/13/2018 10:05 AM, Markus Armbruster wrote:
>> Peter Xu <peterx@redhat.com> writes:
>>=20
>>> Replace existing trace_vtd_err() with error_report_once() then stderr
>>> will capture something if any of the error happens, meanwhile we don't
>>> suffer from any DDOS.  Then remove the trace point.  Since at it,
>>> provide more information where proper (now we can pass parameters into
>>> the report function).
>>>
>>> Reviewed-by: Philippe Mathieu-Daud=C3=A9 <f4bug@amsat.org>
>>> Signed-off-by: Peter Xu <peterx@redhat.com>
>>> ---
>>>  hw/i386/intel_iommu.c | 59 ++++++++++++++++++++++++-------------------
>>>  hw/i386/trace-events  |  1 -
>>>  2 files changed, 33 insertions(+), 27 deletions(-)
>>=20
>> Michael, would you give your Reviewed-by or Acked-by?  I'd take the
>> series through my tree then.
>>=20
>> [...]
>>=20
> Sorry to enter this thread at this late stage. Just one question: on the
> smmuv3 emulation code, Peter (Maydell) urged me to use
> qemu_log_mask(LOG_GUEST_ERROR, ...) whenever the error was triggered by
> a guest bad behavior. So what is the final guidance to avoid the DOS you
> mention?

Does the user need to know about the error condition?

If yes, we should tell him.  Logging is not telling.

Peter, what do you think?