Xen refuses to load minimal dom0 kernel

Xen refuses to load minimal dom0 kernel

[Julian Stecklina]

Hello,

I am trying to link a minimal Domain 0 kernel (adapted from the 
Mini-OS), but when Xen tries to build the Domain 0 it panics:

"Domain 0 allocation is too small for kernel image."

which is caused by the following code in xen/arch/x86/domain_build.c:

     order = get_order_from_bytes(v_end - dsi.v_start);
     if ( (1UL << order) > nr_pages )
         panic("Domain 0 allocation is too small for kernel image.\n");

The linker script I am using is adapted from the Mini-OS and links .text 
  at 0xC0000000 + 0x100000, just like the Linux kernel does. Does any 
one has any hints what I am doing wrong and what this test actually 
checks for?

Regards,
Julian

Re: Xen refuses to load minimal dom0 kernel

[Grzegorz Milos]

> I am trying to link a minimal Domain 0 kernel (adapted from the  
> Mini-OS), but when Xen tries to build the Domain 0 it panics:
>
> "Domain 0 allocation is too small for kernel image."
>
> which is caused by the following code in xen/arch/x86/domain_build.c:
>
>     order = get_order_from_bytes(v_end - dsi.v_start);
>     if ( (1UL << order) > nr_pages )
>         panic("Domain 0 allocation is too small for kernel image.\n");
>
> The linker script I am using is adapted from the Mini-OS and  
> links .text  at 0xC0000000 + 0x100000, just like the Linux kernel  
> does. Does any one has any hints what I am doing wrong and what  
> this test actually checks for?

Mini-OS assumes .text at 0x0. Since you've changed that, you better  
make corresponding changes to VIRT_BASE and ELF_PADDR_OFFSET in mini- 
os/arch/x86/x86_32.S. If that does not help, could you send an output  
of the following printk added just before the if statement?
printk("v_start=%lx v_end=(%lx, %lx)\n", dsi.v_start, v_end, dsi.v_end);

Thanks
Gregor

Re: Xen refuses to load minimal dom0 kernel

[Julian Stecklina]

Grzegorz Milos wrote:
>> I am trying to link a minimal Domain 0 kernel (adapted from the 
>> Mini-OS), but when Xen tries to build the Domain 0 it panics:
>>
>> "Domain 0 allocation is too small for kernel image."
>>
>> which is caused by the following code in xen/arch/x86/domain_build.c:
>>
>>     order = get_order_from_bytes(v_end - dsi.v_start);
>>     if ( (1UL << order) > nr_pages )
>>         panic("Domain 0 allocation is too small for kernel image.\n");
>>
>> The linker script I am using is adapted from the Mini-OS and links 
>> .text  at 0xC0000000 + 0x100000, just like the Linux kernel does. Does 
>> any one has any hints what I am doing wrong and what this test 
>> actually checks for?
> 
> Mini-OS assumes .text at 0x0. Since you've changed that, you better make 
> corresponding changes to VIRT_BASE and ELF_PADDR_OFFSET in 
> mini-os/arch/x86/x86_32.S. If that does not help, could you send an 
> output of the following printk added just before the if statement?
> printk("v_start=%lx v_end=(%lx, %lx)\n", dsi.v_start, v_end, dsi.v_end);

I finally got it to work by closely following what the startup code and 
linker script of the Linux kernel do. Is there any documentation on what 
the hypervisor expects from a Domain 0 and in general how the Domain 0 
environment differs from that of a DomU (e.g., memory management, 
console, xenbus)?

Regards,
Julian

RE: Re: Xen refuses to load minimal dom0 kernel

[Puthiyaparambil, Aravindh]

Julian,

> I am trying to link a minimal Domain 0 kernel (adapted from the
> Mini-OS), but when Xen tries to build the Domain 0 it panics:

What minimal kernel are you using for Dom0? Is it Mini-OS itself or is
it based on some other OS kernel?

Thanks,
Aravindh

Re: Xen refuses to load minimal dom0 kernel

[Julian Stecklina]

Puthiyaparambil, Aravindh wrote:
> Julian,
> 
>> I am trying to link a minimal Domain 0 kernel (adapted from the
>> Mini-OS), but when Xen tries to build the Domain 0 it panics:
> 
> What minimal kernel are you using for Dom0? Is it Mini-OS itself or is
> it based on some other OS kernel?

At the moment it is Mini-OS.

Regards,
Julian

RE: Re: Xen refuses to load minimal dom0 kernel

[Puthiyaparambil, Aravindh]

> > Julian,
> >
> >> I am trying to link a minimal Domain 0 kernel (adapted from the
> >> Mini-OS), but when Xen tries to build the Domain 0 it panics:
> >
> > What minimal kernel are you using for Dom0? Is it Mini-OS itself or
is
> > it based on some other OS kernel?
> 
> At the moment it is Mini-OS.
> 

I am curious to know how you will handle network and block devices. Will
you have a driver domain running by the side of Mini-OS-Dom0?

Thanks,
Aravindh

Re: Xen refuses to load minimal dom0 kernel

[Julian Stecklina]

Puthiyaparambil, Aravindh wrote:
>>> Julian,
>>>
>>>> I am trying to link a minimal Domain 0 kernel (adapted from the
>>>> Mini-OS), but when Xen tries to build the Domain 0 it panics:
>>> What minimal kernel are you using for Dom0? Is it Mini-OS itself or
> is
>>> it based on some other OS kernel?
>> At the moment it is Mini-OS.
>>
> 
> I am curious to know how you will handle network and block devices. Will
> you have a driver domain running by the side of Mini-OS-Dom0?

Yes, this is the general plan. But at the moment the memory issues 
obstruct further experimenting. (See the other thread by me: Mini-OS in 
dom0 - virtual memory problems)

Regards,
Julian