Re: [Xen-devel] Errors with Loading Xen at a Certain Address

[Brian Woods <brian.woods@xxxxxxxxxx>]

On Thu, Oct 03, 2019 at 10:20:36PM +0100, Julien Grall wrote:
> Hi Brian,
> 
> On 10/3/19 9:24 PM, Brian Woods wrote:
> >On Thu, Oct 03, 2019 at 07:23:23PM +0000, Julien Grall wrote:
> >There's a WARN_ON() between the two debug printks calls I shared above.
> 
> Looking at the log, the MFN seems to correspond to the one right after Xen
> (0000000001400000 - 00000000015328f1) in memory.
> 
> So it is normal to have the page given to the boot allocator. However, I am
> not entirely sure which bit of init_done() is giving the page again to
> xenheap.
> 
> It is unlikely to be free_init_memory() because it deal with the init
> section that is not at the end of the binary.
> 
> This would leave discard_initial_modules() but there are a check to skip Xen
> module.
> 
> The call stack only print the address and not the symbol because it
> unregistered the symbols for init. See unregister_init_virtual_memory().
> 
> (XEN) Xen call trace:
> (XEN)    [<000000000021c1a8>] page_alloc.c#free_heap_pages+0x1a8/0x614 (PC)
> (XEN)    [<000000000021c1a8>] page_alloc.c#free_heap_pages+0x1a8/0x614 (LR)
> (XEN)    [<000000000021e900>] page_alloc.c#init_heap_pages+0x3d4/0x564
> (XEN)    [<000000000021eb24>] init_domheap_pages+0x94/0x9c
> (XEN)    [<00000000002b83ec>] 00000000002b83ec
> (XEN)    [<00000000002b8904>] 00000000002b8904
> (XEN)    [<0000000000260a3c>] setup.c#init_done+0x10/0x20
> (XEN)    [<00000000002b99ac>] 00000000002b99ac
> 
> You should be able to use addr2line on the address with Xen binary.
> I have the feeling this will point to discard_initial_modules() as this is
> an init function and the symbol should not be printed.
> 
> But, I can't see anything obviously wrong in the function... So I am not
> entirely sure what could be the next steps.
> 
> Cheers,
> 
> -- 
> Julien Grall

In the log, there's:
(XEN) MODULE[0]: 0000000001400000 - 00000000015328f1 Xen
(XEN) MODULE[1]: 00000000076d2000 - 00000000076dc080 Device Tree
(XEN) MODULE[2]: 00000000076df000 - 0000000007fff364 Ramdisk
(XEN) MODULE[3]: 0000000000080000 - 0000000003180000 Kernel
(XEN)  RESVD[0]: 00000000076d2000 - 00000000076dc000
(XEN)  RESVD[1]: 00000000076df000 - 0000000007fff364

Linux kernel    ->   8_0000 - 318_0000
Xen             -> 140_0000 - 153_28f1

There's something not quite right here... I'm guessing Xen was working
at the address before because it was out of the "range" of the Linux
kernel.  Now I guess I need to look into if it's a Xen or u-boot issue.

-- 
Brian Woods

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