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Re: [Xen-devel] [VMI] Possible race-condition in altp2m APIs
- To: Mathieu Tarral <mathieu.tarral@xxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Fri, 10 May 2019 16:21:23 +0100
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- Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
- Delivery-date: Fri, 10 May 2019 15:21:29 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Openpgp: preference=signencrypt
On 10/05/2019 16:17, Mathieu Tarral wrote:
> Le jeudi, mai 9, 2019 6:42 PM, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> a
> écrit :
>> Therefore, the conclusion to draw is that it is a logical bug somewhere.
>>
>> First of all - ensure you are using up-to-date microcode. The number of
>> errata which have been discovered by people associated with the Xen
>> community is large.
>>
>> The microcode is available from
>> https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/ and
>> https://andrewcoop-xen.readthedocs.io/en/latest/admin-guide/microcode-loading.html
>> is some documentation I prepared earlier.
> I updated my microcode following your instructions.
> I installed the intel-microcode package on Debian stretch, and added
> ucode=scan to my Xen boot command line.
>
> Looking at xl dmesg before the update, I noticed I had a bug that should be
> fix by a microcode update:
> "tsc_deadline disabled due to errata..."
That is actually a Xen bug where we don't scan the current microcode
version if we aren't about to load new microcode. Therefore, it was
likely a red herring before.
I'll try and get a fix sorted properly and tagged for backport.
> This message disappeared with the microcode code update, which is applied at
> boot and can be
> seen in xl dmesg.
> The microcode version is now 0x25 (2018-04-02)
>
> And if I use iucode-tool on the intel-ucode directory, from the repo your
> provided, the only
> microcode that matches has the same release date:
>
> $ iucode-tool -S Intel-Linux-Processor-Microcode-Data-Files/intel-ucode/ -l
> selected microcodes:
> 053/001: sig 0x000306c3, pf_mask 0x32, 2018-04-02, rev 0x0025, size 23552
>
>
> The bug is still here, so we can exclude a microcode issue.
Good - that is one further angle excluded. Always make sure you are
running with up-to-date microcode, but it looks like we back to
investigating a logical bug in libvmi or Xen.
~Andrew
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