Re: [PATCH 0/5] ia64 ski emulator patches

[Mikael Pettersson]

Mikael Pettersson writes:
 > Mikulas Patocka writes:
 >  > 
 >  > 
 >  > On Sat, 25 Jan 2014, Mikael Pettersson wrote:
 >  > 
 >  > > My ski patches are in 
 > 
 >  > > for now.  I'll post the kernel patches to linux-ia64 @ vger in a few 
 > minutes.
 >  > > 
 >  > > /Mikael
 >  > 
 >  > Thanks for the patches.
 >  > 
 >  > Isn't this subject to races? - could it lock up if the signal happens 
 > just 
 >  > before the pause syscall?
 >  > 
 >  > +case SSC_HALT_LIGHT:
 >  > +  /* Sleep until SIGIO or SIGALRM is received; this relies on
 >  > +keyboard/ethernet input being detected via SIGIO, and the
 >  > +ITC now being emulated via setitimer() and SIGALRM.  */
 >  > +  pause ();
 >  > +  break;
 >  > +
 > 
 > Thanks for the review. You're right, the pause mustn't happen if
 > itc_itimer_fired == 1.  Let me ponder this for a while...

Ok, I've fixed this in two different ways: one patch which uses pselect,
and one patch which uses plain select + the self-pipe trick.  Both work
in limited testing, but the pselect one is much nicer and appears to have
a little less host CPU overhead, so that's the one I'm stress-testing now.

Both patches have been uploaded to the same place as before.

/Mikael
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Re: [PATCH 0/5] ia64 ski emulator patches

[Mikael Pettersson]

Mikulas Patocka writes:
 > 
 > 
 > On Sat, 25 Jan 2014, Mikael Pettersson wrote:
 > 
 > > My ski patches are in 
 > > 
 > > for now.  I'll post the kernel patches to linux-ia64 @ vger in a few 
 > > minutes.
 > > 
 > > /Mikael
 > 
 > Thanks for the patches.
 > 
 > Isn't this subject to races? - could it lock up if the signal happens just 
 > before the pause syscall?
 > 
 > +case SSC_HALT_LIGHT:
 > +  /* Sleep until SIGIO or SIGALRM is received; this relies on
 > +keyboard/ethernet input being detected via SIGIO, and the
 > +ITC now being emulated via setitimer() and SIGALRM.  */
 > +  pause ();
 > +  break;
 > +

Thanks for the review. You're right, the pause mustn't happen if
itc_itimer_fired == 1.  Let me ponder this for a while...

/Mikael
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Re: [PATCH 0/5] ia64 ski emulator patches

[Mikulas Patocka]

On Sat, 25 Jan 2014, Mikael Pettersson wrote:

> My ski patches are in 
> 
> for now.  I'll post the kernel patches to linux-ia64 @ vger in a few minutes.
> 
> /Mikael

Thanks for the patches.

Isn't this subject to races? - could it lock up if the signal happens just 
before the pause syscall?

+case SSC_HALT_LIGHT:
+  /* Sleep until SIGIO or SIGALRM is received; this relies on
+keyboard/ethernet input being detected via SIGIO, and the
+ITC now being emulated via setitimer() and SIGALRM.  */
+  pause ();
+  break;
+

Mikulas
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RE: [PATCH 0/5] ia64 ski emulator patches

[Mikael Pettersson]

Luck, Tony writes:
 > Mikulas:
 > >> Here I'm sending some ia64 patches to make it work in the ski emulator. 
 > >> This has been broken for a long time.
 > 
 > Thanks - There are questions from time to time on how to test ia64
 > for those people who do not have hardware.
 > 
 > Mikael:
 > > Thanks.  I've recently started running 3.x kernels on ia64 via ski,
 > > but I'm getting random kernel crashes with 3.13.  I'll give your
 > > patches a try shortly.
 > 
 > Let me know how that goes - I haven't used ski in a decade and
 > have quite forgotten how to set it up.

It seems my kernel crashes were due to using gcc-4.8.2 to compile ski,
going back to gcc-4.7.3 for ski, and gcc-4.3.6 for cross-compiling
the kernel, gives me a solid emulated system.

 > > I've written a few patches to improve other aspects of running the
 > > kernel on ski:
 > > - kernel patch to turn PAL_HALT_LIGHT into a new SSC_HALT_LIGHT,
 > >   and a corresponing ski patch to pause() on SSC_HALT_LIGHT; this
 > >   together with the fixed-frequency ITC patch allows ski to idle
 > >   with very low host CPU overhead when the guest kernel idles
 > > - kernel patch to bump the RAM size from 130MB to 2GB
 > >
 > > I'd be happy to share these patches if there's interest in them.
 > 
 > It seems that there are at least two of you out there - so I'm happy
 > to take kernel patches that make things better.  Not sure where the
 > ski patches go - is someone maintaining that?

The ski project on sourceforge seems dead, nothing have been posted
on its mailing list since 2008, and the web interface for browsing
the source repo is broken.  Red Hat, Gentoo, and Debian package ski
with a few common build fixes, but that's it.

/Mikael
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Re: [PATCH 0/5] ia64 ski emulator patches

[Mikael Pettersson]

Mikulas Patocka writes:
 > 
 > 
 > On Fri, 24 Jan 2014, Mikael Pettersson wrote:
 > 
 > > Mikulas Patocka writes:
 > >  > Hi
 > >  > 
 > >  > Here I'm sending some ia64 patches to make it work in the ski emulator. 
 > >  > This has been broken for a long time.
 > > 
 > > Thanks.  I've recently started running 3.x kernels on ia64 via ski,
 > > but I'm getting random kernel crashes with 3.13.  I'll give your
 > > patches a try shortly.
 > 
 > I also had some random page-table corruption when running recent kernels 
 > in ski. The problems occured when upgrading the whole Debian distribution. 
 > Kernel 2.6.8 was solid, new kernels caused problems, I don't know why.

What I've seen so far seems to indicate that gcc-4.8.2 miscompiles ski,
resulting in kernel oopses, and _possibly_ that gcc-4.7.3 miscompiles
the kernel.  Ski compiled by gcc-4.7.3 (on x86_64) running a kernel
compiled by gcc-4.3.6 seems to be a solid combination for me.

 > > I've written a few patches to improve other aspects of running the
 > > kernel on ski:
 > > - ski patch to use tun/tap networking (no need to run ski as root)
 > > - ski patch to implement a fixed-frequency ITC (the ITC is currently
 > >   highly variable, completely breaking basic timekeeping)
 > > - kernel patch to turn PAL_HALT_LIGHT into a new SSC_HALT_LIGHT,
 > >   and a corresponing ski patch to pause() on SSC_HALT_LIGHT; this
 > >   together with the fixed-frequency ITC patch allows ski to idle
 > >   with very low host CPU overhead when the guest kernel idles
 > > - kernel patch to bump the RAM size from 130MB to 2GB
 > > 
 > > I'd be happy to share these patches if there's interest in them.
 > > 
 > > /Mikael
 > 
 > I would be interested in them. I also patched that timekeeping issue in 
 > ski.

My ski patches are in 

for now.  I'll post the kernel patches to linux-ia64 @ vger in a few minutes.

/Mikael
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Re: [PATCH 0/5] ia64 ski emulator patches

[Mikael Pettersson]

Mikulas Patocka writes:
 > 
 > 
 > On Fri, 24 Jan 2014, Mikael Pettersson wrote:
 > 
 > > Mikulas Patocka writes:
 > >  > Hi
 > >  > 
 > >  > Here I'm sending some ia64 patches to make it work in the ski emulator. 
 > >  > This has been broken for a long time.
 > > 
 > > Thanks.  I've recently started running 3.x kernels on ia64 via ski,
 > > but I'm getting random kernel crashes with 3.13.  I'll give your
 > > patches a try shortly.
 > 
 > BTW. does the kernel boot for you without that _STK_LIM_MAX change? For 
 > me, _STK_LIM_MAX was a showstopper, it wasn't able to spawn any userspace 
 > process without this patch.

Yes, everything works fine for me without your _STK_LIM_MAX change.
My ski VMs currently run 3.12 kernels with Fedora 9 user-space.

/Mikael
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RE: [PATCH 0/5] ia64 ski emulator patches

[Luck, Tony]

Mikulas:
>> Here I'm sending some ia64 patches to make it work in the ski emulator. 
>> This has been broken for a long time.

Thanks - There are questions from time to time on how to test ia64
for those people who do not have hardware.

Mikael:
> Thanks.  I've recently started running 3.x kernels on ia64 via ski,
> but I'm getting random kernel crashes with 3.13.  I'll give your
> patches a try shortly.

Let me know how that goes - I haven't used ski in a decade and
have quite forgotten how to set it up.

> I've written a few patches to improve other aspects of running the
> kernel on ski:
> - kernel patch to turn PAL_HALT_LIGHT into a new SSC_HALT_LIGHT,
>   and a corresponing ski patch to pause() on SSC_HALT_LIGHT; this
>   together with the fixed-frequency ITC patch allows ski to idle
>   with very low host CPU overhead when the guest kernel idles
> - kernel patch to bump the RAM size from 130MB to 2GB
>
> I'd be happy to share these patches if there's interest in them.

It seems that there are at least two of you out there - so I'm happy
to take kernel patches that make things better.  Not sure where the
ski patches go - is someone maintaining that?

-Tony
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Re: [PATCH 0/5] ia64 ski emulator patches

[Mikulas Patocka]

On Fri, 24 Jan 2014, Mikael Pettersson wrote:

> Mikulas Patocka writes:
>  > Hi
>  > 
>  > Here I'm sending some ia64 patches to make it work in the ski emulator. 
>  > This has been broken for a long time.
> 
> Thanks.  I've recently started running 3.x kernels on ia64 via ski,
> but I'm getting random kernel crashes with 3.13.  I'll give your
> patches a try shortly.

BTW. does the kernel boot for you without that _STK_LIM_MAX change? For 
me, _STK_LIM_MAX was a showstopper, it wasn't able to spawn any userspace 
process without this patch.

Mikulkas
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Re: [PATCH 0/5] ia64 ski emulator patches

[Mikulas Patocka]

On Fri, 24 Jan 2014, Mikael Pettersson wrote:

> Mikulas Patocka writes:
>  > Hi
>  > 
>  > Here I'm sending some ia64 patches to make it work in the ski emulator. 
>  > This has been broken for a long time.
> 
> Thanks.  I've recently started running 3.x kernels on ia64 via ski,
> but I'm getting random kernel crashes with 3.13.  I'll give your
> patches a try shortly.

I also had some random page-table corruption when running recent kernels 
in ski. The problems occured when upgrading the whole Debian distribution. 
Kernel 2.6.8 was solid, new kernels caused problems, I don't know why.

> I've written a few patches to improve other aspects of running the
> kernel on ski:
> - ski patch to use tun/tap networking (no need to run ski as root)
> - ski patch to implement a fixed-frequency ITC (the ITC is currently
>   highly variable, completely breaking basic timekeeping)
> - kernel patch to turn PAL_HALT_LIGHT into a new SSC_HALT_LIGHT,
>   and a corresponing ski patch to pause() on SSC_HALT_LIGHT; this
>   together with the fixed-frequency ITC patch allows ski to idle
>   with very low host CPU overhead when the guest kernel idles
> - kernel patch to bump the RAM size from 130MB to 2GB
> 
> I'd be happy to share these patches if there's interest in them.
> 
> /Mikael

I would be interested in them. I also patched that timekeeping issue in 
ski.

Mikulas
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Re: [PATCH 0/5] ia64 ski emulator patches

[Mikael Pettersson]

Mikulas Patocka writes:
 > Hi
 > 
 > Here I'm sending some ia64 patches to make it work in the ski emulator. 
 > This has been broken for a long time.

Thanks.  I've recently started running 3.x kernels on ia64 via ski,
but I'm getting random kernel crashes with 3.13.  I'll give your
patches a try shortly.

I've written a few patches to improve other aspects of running the
kernel on ski:
- ski patch to use tun/tap networking (no need to run ski as root)
- ski patch to implement a fixed-frequency ITC (the ITC is currently
  highly variable, completely breaking basic timekeeping)
- kernel patch to turn PAL_HALT_LIGHT into a new SSC_HALT_LIGHT,
  and a corresponing ski patch to pause() on SSC_HALT_LIGHT; this
  together with the fixed-frequency ITC patch allows ski to idle
  with very low host CPU overhead when the guest kernel idles
- kernel patch to bump the RAM size from 130MB to 2GB

I'd be happy to share these patches if there's interest in them.

/Mikael
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