lguest over qemu

lguest over qemu

[Matias Zabaljauregui]

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Hi,

I'm setting my lguest playing environment with qemu, but didn't have a good
start... maybe because my modest laptop only has 512Mb of RAM.

This is my qemu  command:

                         qemu -s -no-kqemu -m 400 -hda linux26.img  -net
nic,model=rtl8139 -net tap


( linux26.img  includes  a  2.6.21.5 kernel with the lguest-2.6.21-307patch  )


This is my lguest command (executed within the qemu VM):

                          ./lguest 64m /boot/kernel-2.6.21.5 --block=
initrd-1.1-i386.img root=/dev/lbga

always get this message (I have insisted with different virtual ram
amounts):

                    lguest: failed to get page 167304



thank you in advance
Matias Zabaljauregui

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Re: lguest over qemu

[Rusty Russell]

On Wed, 2007-07-11 at 11:51 +0200, Matias Zabaljauregui wrote:
> Hi, 
> 
> I'm setting my lguest playing environment with qemu, but didn't have a
> good start... maybe because my modest laptop only has 512Mb of RAM.
> 
> This is my qemu  command:
> 
>                          qemu -s -no-kqemu -m 400 -hda linux26.img
> -net nic,model=rtl8139 -net tap
> 
> 
> ( linux26.img  includes  a  2.6.21.5 kernel with the lguest-2.6.21-307
> patch  )
> 
> 
> This is my lguest command (executed within the qemu VM): 
> 
>                           ./lguest 64m /boot/kernel-2.6.21.5
> --block=initrd-1.1-i386.img root=/dev/lbga
> 
> always get this message (I have insisted with different virtual ram
> amounts): 
> 
>                     lguest: failed to get page 167304

I did most of my development under qemu, so I don't think that's the
issue.  Can you send me your .config?

Thanks,
Rusty.

Re: lguest over qemu

[Matias Zabaljauregui]

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Rusty,

You were right, it was the kernel configuration.
Changing the subject, in the next month I will be studying the possibilities
of implementing the idea behind xenoprof, for lguest.
Do you think this can be useful ?
Any advice?

Thanks
Matias


2007/7/12, Rusty Russell <rusty@rustcorp.com.au>:
>
> On Wed, 2007-07-11 at 11:51 +0200, Matias Zabaljauregui wrote:
> > Hi,
> >
> > I'm setting my lguest playing environment with qemu, but didn't have a
> > good start... maybe because my modest laptop only has 512Mb of RAM.
> >
> > This is my qemu  command:
> >
> >                          qemu -s -no-kqemu -m 400 -hda linux26.img
> > -net nic,model=rtl8139 -net tap
> >
> >
> > ( linux26.img  includes  a  2.6.21.5 kernel with the lguest-2.6.21-307
> > patch  )
> >
> >
> > This is my lguest command (executed within the qemu VM):
> >
> >                           ./lguest 64m /boot/kernel-2.6.21.5
> > --block=initrd-1.1-i386.img root=/dev/lbga
> >
> > always get this message (I have insisted with different virtual ram
> > amounts):
> >
> >                     lguest: failed to get page 167304
>
> I did most of my development under qemu, so I don't think that's the
> issue.  Can you send me your .config?
>
> Thanks,
> Rusty.
>
>

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Re: lguest over qemu

[Rusty Russell]

On Thu, 2007-07-12 at 17:02 +0200, Matias Zabaljauregui wrote:
> Rusty, 
> 
> You were right, it was the kernel configuration. 

Hi Matias,

	Any chance you could tell me what configuration option broke lguest?  I
should either fix it or document it...

> Changing the subject, in the next month I will be studying the
> possibilities of implementing the idea behind xenoprof, for lguest. 
> Do you think this can be useful ?  
> Any advice? 

	One purpose of lguest is to demonstrate how virtualization should work,
so including profiling support is useful.  But the other purpose of
lguest is to be simple, so it depends how simple the patch to lguest
is...

	(Note that lguest doesn't support NMIs, but Steven has code for NMI
support for lguest-x86-64 which could be ported across).

Cheers!
Rusty.

Re: lguest over qemu

[Steven Rostedt]

>
> 	(Note that lguest doesn't support NMIs, but Steven has code for NMI
> support for lguest-x86-64 which could be ported across).

Rusty,

About that.  Is there a way to get a NMI only stack in i386? In x86_64
it's part of the TSS. So I can always know I have a good stack for the
NMI. I'm not sure i368 has the same thing. Or do we always have a good
stack whenever we are in ring0?

Oh, and btw, I've just rewrote all of the Lguest64 page table handling.
I'm just going over one design change that is really bothering me. In
x86_64 we can have 2M or 4k pages (like the PSE in i386). But since 4K
pages are used by the shadow page tables, I have to map them like that.
But this means that I can have the same guest address as both a PMD and a
PTE. Which is breaking some of my code. I'm working on a fix as I write
this.

But to get you up-to-date to where I'm at. I've implemented a way to have
the HV mapped uniquely for all VCPUs.  So there's a HV text section (the
same for all VCPUs), a HV VCPU Data section (readonly in all rings with
guest cr3), and a HV VCPU Scratch Pad section (read/write in rings
0,1,and2).  So now the guest kernel runs in ring 1. With this change, I
already implemented a syscall trampoline that no longer needs to switch to
the host, as well as iretq by the guest kernel goes directly to the guest
user space (or kernel).  The next version of lguest64 will be much cleaner
and faster!!!!

-- Steve

Re: lguest over qemu

[Rusty Russell]

On Thu, 2007-07-12 at 20:41 -0400, Steven Rostedt wrote:
> >
> > 	(Note that lguest doesn't support NMIs, but Steven has code for NMI
> > support for lguest-x86-64 which could be ported across).
> 
> Rusty,
> 
> About that.  Is there a way to get a NMI only stack in i386? In x86_64
> it's part of the TSS. So I can always know I have a good stack for the
> NMI. I'm not sure i368 has the same thing. Or do we always have a good
> stack whenever we are in ring0?

Yeah, we always have a good stack.  It might have some stuff pushed on
it if we were in the middle of a switch, but that's OK.

> Oh, and btw, I've just rewrote all of the Lguest64 page table handling.
> I'm just going over one design change that is really bothering me. In
> x86_64 we can have 2M or 4k pages (like the PSE in i386). But since 4K
> pages are used by the shadow page tables, I have to map them like that.
> But this means that I can have the same guest address as both a PMD and a
> PTE. Which is breaking some of my code. I'm working on a fix as I write
> this.

This would be a good place to share with KVM, I think.  (Or at least
look at what they did here).

> But to get you up-to-date to where I'm at. I've implemented a way to have
> the HV mapped uniquely for all VCPUs.  So there's a HV text section (the
> same for all VCPUs), a HV VCPU Data section (readonly in all rings with
> guest cr3), and a HV VCPU Scratch Pad section (read/write in rings
> 0,1,and2).  So now the guest kernel runs in ring 1. With this change, I
> already implemented a syscall trampoline that no longer needs to switch to
> the host, as well as iretq by the guest kernel goes directly to the guest
> user space (or kernel).  The next version of lguest64 will be much cleaner
> and faster!!!!

Awesome!  Good to see the puppies run free...

Cheers,
Rusty.

Re: lguest over qemu

[Eric Van Hensbergen]

On 7/11/07, Rusty Russell <rusty@rustcorp.com.au> wrote:
> > always get this message (I have insisted with different virtual ram
> > amounts):
> >
> >                     lguest: failed to get page 167304
>
> I did most of my development under qemu, so I don't think that's the
> issue.  Can you send me your .config?
>

I had a different problem which was when I was running a kernel with
WDT's enabled, I was getting a:
   lguest: bad page table entry

Both the advantechwdt and the alimi7101 WDT's were initializing and
reporting I/O address 0x0443 already in use.

I removed the WDT's from the configuration and everything was fine.

          -eric

Re: lguest over qemu

[Rusty Russell]

On Sat, 2007-08-25 at 10:48 -0500, Eric Van Hensbergen wrote:
> On 7/11/07, Rusty Russell <rusty@rustcorp.com.au> wrote:
> > > always get this message (I have insisted with different virtual ram
> > > amounts):
> > >
> > >                     lguest: failed to get page 167304
> >
> > I did most of my development under qemu, so I don't think that's the
> > issue.  Can you send me your .config?
> >
> 
> I had a different problem which was when I was running a kernel with
> WDT's enabled, I was getting a:
>    lguest: bad page table entry
> 
> Both the advantechwdt and the alimi7101 WDT's were initializing and
> reporting I/O address 0x0443 already in use.
> 
> I removed the WDT's from the configuration and everything was fine.

Interesting.  Enabling them here gives the expected messages:

        WDT driver for Advantech single board computer initialising.
        advantechwdt: I/O address 0x0443 already in use
        advantechwdt: probe of advantechwdt failed with error -5
        alim7101_wdt: Steve Hill <steve@navaho.co.uk>.
        alim7101_wdt: ALi M7101 PMU not present - WDT not set
        
But it boots fine.

Perhaps it's a hardware difference (we do expose some of the host CPU
capabilities to the guest), or perhaps some other config difference
which is masking the problem?

Thanks,
Rusty.

Re: lguest over qemu

[Eric Van Hensbergen]

On 8/25/07, Rusty Russell <rusty@rustcorp.com.au> wrote:
> On Sat, 2007-08-25 at 10:48 -0500, Eric Van Hensbergen wrote:
>
> Interesting.  Enabling them here gives the expected messages:
>
>         WDT driver for Advantech single board computer initialising.
>         advantechwdt: I/O address 0x0443 already in use
>         advantechwdt: probe of advantechwdt failed with error -5
>         alim7101_wdt: Steve Hill <steve@navaho.co.uk>.
>         alim7101_wdt: ALi M7101 PMU not present - WDT not set
>
> But it boots fine.
>
> Perhaps it's a hardware difference (we do expose some of the host CPU
> capabilities to the guest), or perhaps some other config difference
> which is masking the problem?
>

Okay, I am running this on a quad opteron - although I'm using a i386
qemu.  Still - its strange that disabling the watchdog allows my
kernel to boot fine...

              -eric