Re: Xen 3.3: Problem HVM guest

[Christoph Egger <Christoph_Egger%gmx.de@localhost>]

Christoph Egger wrote:
> Hi,
>
> When launching a HVM guest, the process hangs and does not even block 
> any xmlrpc communication, there's a significant system slowdown until 
> reboot.
>
> I finally indentified the place of hang. It is in the xentools33 package
> in ${WRKSRC}/libxc/xc_hvm_build.c , function setup_guest().
>
> At the end of setup_guest(), there's this junk of code:
>
>
>
>     /* Insert JMP <rel32> instruction at address 0x0 to reach entry 
> point. */
>     entry_eip = elf_uval(&elf, elf.ehdr, e_entry);
>     if ( entry_eip != 0 )    {
>         char *page0 = xc_map_foreign_range(
>             xc_handle, dom, PAGE_SIZE, PROT_READ | PROT_WRITE, 0);
>         if ( page0 == NULL )
>             goto error_out;
>         page0[0] = 0xe9;               <------------ "hang"
>         *(uint32_t *)&page0[1] = entry_eip - 5;
>         munmap(page0, PAGE_SIZE);
>     }
>
>
> The "hang" happens when executing page0[0] = 0xe9;
>
> I'm CC this to tech-kern, because I'm not sure if this is a bug in 
> xentools or if I found a UVM/pmap bug.

Here is an URL to the diff where this hunk has been added including the 
commit log:

http://xenbits.xensource.com/xen-unstable.hg/rev/772674585a1a

Christoph