Question about "xen: Revert commits da72ff5bfcb0 and 72a9b186292d"

Question about "xen: Revert commits da72ff5bfcb0 and 72a9b186292d"

[Jean-Louis Dupond]

Hi All,

We had some issues with BSOD's on Windows at startup when using some old 
Xen drivers inside Windows.
Now when we upgrade to the most recent 4.9.x kernel. The issue seems to 
be resolved.

Could it be that the following commit fixes the issue:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=84d582d236dc1f9085e741affc72e9ba061a67c2
?

As far as I can see it only breaks Xen < 4.0. But could it be it also 
breaks Windows VM's with old Xen drivers?

Thanks
Jean-Louis

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Re: Question about "xen: Revert commits da72ff5bfcb0 and 72a9b186292d"

[Juergen Gross]

On 04/07/17 13:54, Jean-Louis Dupond wrote:
> Hi All,
> 
> We had some issues with BSOD's on Windows at startup when using some old
> Xen drivers inside Windows.
> Now when we upgrade to the most recent 4.9.x kernel. The issue seems to
> be resolved.
> 
> Could it be that the following commit fixes the issue:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=84d582d236dc1f9085e741affc72e9ba061a67c2
> 
> ?
> 
> As far as I can see it only breaks Xen < 4.0. But could it be it also
> breaks Windows VM's with old Xen drivers?

Umm, I don't get it.

Are you using Windows or Linux? Above commit is for the Linux kernel
running as HVM domain. It shouldn't be able to modify behavior of a
Windows guest at all.


Juergen

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Re: Question about "xen: Revert commits da72ff5bfcb0 and 72a9b186292d"

[Jean-Louis Dupond]

Hi Juergen,

We run Xen as dom0 with Windows domU's.

Now with older 4.9.x kernels, we had BSOD's when we booted a domU with 
old Xen drivers in it.
With the newest kernel (4.9.34), this seems to be resolved.

I was wondering what caused this. And that patch triggered my attention 
:)

Thanks
Jean-Louis

Op 2017-07-04 14:40, schreef Juergen Gross:
> On 04/07/17 13:54, Jean-Louis Dupond wrote:
>> Hi All,
>> 
>> We had some issues with BSOD's on Windows at startup when using some 
>> old
>> Xen drivers inside Windows.
>> Now when we upgrade to the most recent 4.9.x kernel. The issue seems 
>> to
>> be resolved.
>> 
>> Could it be that the following commit fixes the issue:
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=84d582d236dc1f9085e741affc72e9ba061a67c2
>> 
>> ?
>> 
>> As far as I can see it only breaks Xen < 4.0. But could it be it also
>> breaks Windows VM's with old Xen drivers?
> 
> Umm, I don't get it.
> 
> Are you using Windows or Linux? Above commit is for the Linux kernel
> running as HVM domain. It shouldn't be able to modify behavior of a
> Windows guest at all.
> 
> 
> Juergen

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Re: Question about "xen: Revert commits da72ff5bfcb0 and 72a9b186292d"

[Juergen Gross]

On 04/07/17 14:44, Jean-Louis Dupond wrote:
> Hi Juergen,
> 
> We run Xen as dom0 with Windows domU's.
> 
> Now with older 4.9.x kernels, we had BSOD's when we booted a domU with
> old Xen drivers in it.
> With the newest kernel (4.9.34), this seems to be resolved.
> 
> I was wondering what caused this. And that patch triggered my attention :)

No, I don't think this patch can be the reason.

Which was the latest dom0 kernel causing failure? Or could it be you
upgraded the hypervisor or Xen tools at the same time and the kernel
version just doesn't matter?


Juergen

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Re: Question about "xen: Revert commits da72ff5bfcb0 and 72a9b186292d"

[Jean-Louis Dupond]

Op 2017-07-04 14:51, schreef Juergen Gross:
> On 04/07/17 14:44, Jean-Louis Dupond wrote:
>> Hi Juergen,
>> 
>> We run Xen as dom0 with Windows domU's.
>> 
>> Now with older 4.9.x kernels, we had BSOD's when we booted a domU with
>> old Xen drivers in it.
>> With the newest kernel (4.9.34), this seems to be resolved.
>> 
>> I was wondering what caused this. And that patch triggered my 
>> attention :)
> 
> No, I don't think this patch can be the reason.
> 
> Which was the latest dom0 kernel causing failure? Or could it be you
> upgraded the hypervisor or Xen tools at the same time and the kernel
> version just doesn't matter?
> 
> 
> Juergen

We switched from 3.18 -> 4.9 (using CentOS VIRT), and started to see the 
issue.
If we just upgrade the kernel to latest 4.9, it works fine again.

So something broke it, but its fixed now ...
Was just wondering what caused it exactly :)

Jean-Louis

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