Re: Xen refuses to load minimal dom0 kernel

[Julian Stecklina <der_julian@web.de>]

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