From: Jan Beulich <jbeulich@suse.com>
To: Elliott Mitchell <ehem+xen@m5p.com>
Cc: xen-devel@lists.xenproject.org
Subject: Re: HVM/PVH Balloon crash
Date: Wed, 15 Sep 2021 08:05:05 +0200 [thread overview]
Message-ID: <3efe115b-1ff7-dcf1-8198-37bd7d7fb52f@suse.com> (raw)
In-Reply-To: <YUFdIPLo1AfM5BT2@mattapan.m5p.com>
On 15.09.2021 04:40, Elliott Mitchell wrote:
> On Tue, Sep 07, 2021 at 05:57:10PM +0200, Jan Beulich wrote:
>> On 07.09.2021 17:03, Elliott Mitchell wrote:
>>> Could be this system is in an
>>> intergenerational hole, and some spot in the PVH/HVM code makes an
>>> assumption of the presence of NPT guarantees presence of an operational
>>> IOMMU. Otherwise if there was some copy and paste while writing IOMMU
>>> code, some portion of the IOMMU code might be checking for presence of
>>> NPT instead of presence of IOMMU.
>>
>> This is all very speculative; I consider what you suspect not very likely,
>> but also not entirely impossible. This is not the least because for a
>> long time we've been running without shared page tables on AMD.
>>
>> I'm afraid without technical data and without knowing how to repro, I
>> don't see a way forward here.
>
> Downtimes are very expensive even for lower-end servers. Plus there is
> the issue the system wasn't meant for development and thus never had
> appropriate setup done.
>
> Experimentation with a system of similar age suggested another candidate.
> System has a conventional BIOS. Might some dependancies on the presence
> of UEFI snuck into the NPT code?
I can't think of any such, but as all of this is very nebulous I can't
really rule out anything.
Jan
next prev parent reply other threads:[~2021-09-15 6:05 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-05 22:10 HVM/PVH Ballon crash Elliott Mitchell
2021-09-06 7:52 ` Jan Beulich
2021-09-06 20:47 ` HVM/PVH Balloon crash Elliott Mitchell
2021-09-07 8:03 ` Jan Beulich
2021-09-07 15:03 ` Elliott Mitchell
2021-09-07 15:57 ` Jan Beulich
2021-09-07 21:40 ` Elliott Mitchell
2021-09-15 2:40 ` Elliott Mitchell
2021-09-15 6:05 ` Jan Beulich [this message]
2021-09-26 22:53 ` Elliott Mitchell
2021-09-29 13:32 ` Jan Beulich
2021-09-29 15:31 ` Elliott Mitchell
2021-09-30 7:08 ` Jan Beulich
2021-10-02 2:35 ` Elliott Mitchell
2021-10-07 7:20 ` Jan Beulich
2021-09-30 7:43 ` Jan Beulich
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