Kernel panic on current amd64 running under Ubuntu KVM (patch included)

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Re: Kernel panic on current amd64 running under Ubuntu KVM (patch included)

Alexey Suslikov
On Mon, May 20, 2013 at 9:11 PM, Theo de Raadt <[hidden email]> wrote:
>> I'm not trying to convince, but avoid useless work/talk in the future:
>
> Yes you are.  You have an agenda.
>
> You want to make us work around a bug, rather than talk to the
> originators of the problem.

While I see practical use, someone don't. I call this disagreement. There is
no problem for me if somebody disagree with a plan I have. It's normal.

Btw, Intel's doc I have found at
http://www.intel.com/content/dam/www/public/us/en/documents/application-notes/processor-identification-cpuid-instruction-note.pdf

says "31 Not Used Always returns 0".

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Re: Kernel panic on current amd64 running under Ubuntu KVM (patch included)

Ted Unangst-6
In reply to this post by Theo de Raadt
On Mon, May 20, 2013 at 21:28, Alexey Suslikov wrote:
>
> While I see practical use, someone don't. I call this disagreement. There is
> no problem for me if somebody disagree with a plan I have. It's normal.
>
> Btw, Intel's doc I have found at
> http://www.intel.com/content/dam/www/public/us/en/documents/application-notes/processor-identification-cpuid-instruction-note.pdf
>
>
> says "31 Not Used Always returns 0".

In that case, there's no sense testing for it, because it's always 0.

If it isn't 0, then it's not an amd64 computer and we don't support
it. Trying to identify all the infinite machines we don't support is
fruitless, imo, and perhaps not a path we should start down, because
then people will expect us to detect why we don't run on *their* not
supported computer.

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Re: Kernel panic on current amd64 running under Ubuntu KVM (patch included)

Alexey Suslikov
On Mon, May 20, 2013 at 11:58 PM, Ted Unangst <[hidden email]> wrote:

> On Mon, May 20, 2013 at 21:28, Alexey Suslikov wrote:
>>
>> While I see practical use, someone don't. I call this disagreement. There is
>> no problem for me if somebody disagree with a plan I have. It's normal.
>>
>> Btw, Intel's doc I have found at
>> http://www.intel.com/content/dam/www/public/us/en/documents/application-notes/processor-identification-cpuid-instruction-note.pdf
>>
>>
>> says "31 Not Used Always returns 0".
>
> In that case, there's no sense testing for it, because it's always 0.
>
> If it isn't 0, then it's not an amd64 computer and we don't support
> it. Trying to identify all the infinite machines we don't support is
> fruitless, imo, and perhaps not a path we should start down, because
> then people will expect us to detect why we don't run on *their* not
> supported computer.

In practice, it is not zero. This is why my point was opposite:

* if I see Hypervisor flag in dmesg, my (virtual) hardware is not guaranteed
to operate properly (which is not theoretically, but practically true, because
of crash we have).

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Re: Kernel panic on current amd64 running under Ubuntu KVM (patch included)

Theo de Raadt
In reply to this post by Roman Kravchuk
> On Mon, May 20, 2013 at 11:58 PM, Ted Unangst <[hidden email]> wrote:
> > On Mon, May 20, 2013 at 21:28, Alexey Suslikov wrote:
> >>
> >> While I see practical use, someone don't. I call this disagreement. There is
> >> no problem for me if somebody disagree with a plan I have. It's normal.
> >>
> >> Btw, Intel's doc I have found at
> >> http://www.intel.com/content/dam/www/public/us/en/documents/application-notes/processor-identification-cpuid-instruction-note.pdf
> >>
> >>
> >> says "31 Not Used Always returns 0".
> >
> > In that case, there's no sense testing for it, because it's always 0.
> >
> > If it isn't 0, then it's not an amd64 computer and we don't support
> > it. Trying to identify all the infinite machines we don't support is
> > fruitless, imo, and perhaps not a path we should start down, because
> > then people will expect us to detect why we don't run on *their* not
> > supported computer.
>
> In practice, it is not zero. This is why my point was opposite:
>
> * if I see Hypervisor flag in dmesg, my (virtual) hardware is not guaranteed
> to operate properly (which is not theoretically, but practically true, because
> of crash we have).

Well, gee, it sure sounds like KVM is violating Intel's specification.

We should not fix this.

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Re: Kernel panic on current amd64 running under Ubuntu KVM (patch included)

Alexey Suslikov
On Tue, May 21, 2013 at 12:21 AM, Theo de Raadt <[hidden email]> wrote:

>> On Mon, May 20, 2013 at 11:58 PM, Ted Unangst <[hidden email]> wrote:
>> > On Mon, May 20, 2013 at 21:28, Alexey Suslikov wrote:
>> >>
>> >> While I see practical use, someone don't. I call this disagreement. There is
>> >> no problem for me if somebody disagree with a plan I have. It's normal.
>> >>
>> >> Btw, Intel's doc I have found at
>> >> http://www.intel.com/content/dam/www/public/us/en/documents/application-notes/processor-identification-cpuid-instruction-note.pdf
>> >>
>> >>
>> >> says "31 Not Used Always returns 0".
>> >
>> > In that case, there's no sense testing for it, because it's always 0.
>> >
>> > If it isn't 0, then it's not an amd64 computer and we don't support
>> > it. Trying to identify all the infinite machines we don't support is
>> > fruitless, imo, and perhaps not a path we should start down, because
>> > then people will expect us to detect why we don't run on *their* not
>> > supported computer.
>>
>> In practice, it is not zero. This is why my point was opposite:
>>
>> * if I see Hypervisor flag in dmesg, my (virtual) hardware is not guaranteed
>> to operate properly (which is not theoretically, but practically true, because
>> of crash we have).
>
> Well, gee, it sure sounds like KVM is violating Intel's specification.
>
> We should not fix this.

$ grep -R "bugs@" /usr/src/sys/*

/usr/src/sys/dev/usb/ubsa.c:                "Please send your dmesg to
<[hidden email]>, thanks.\n",
/usr/src/sys/dev/usb/umsm.c:                "Please send your dmesg to
<[hidden email]>, thanks.\n",

Sometimes we warn users, sometimes not (but we aware of the problem).

What is the criteria?

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Re: Kernel panic on current amd64 running under Ubuntu KVM (patch included)

Ted Unangst-6
In reply to this post by Theo de Raadt
On Tue, May 21, 2013 at 00:32, Alexey Suslikov wrote:

> Sometimes we warn users, sometimes not (but we aware of the problem).
>
> What is the criteria?

Is it a device we claim to support? (Or are interested in supporting?)

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