Re: [Xen-devel] Different esps

[Steven Hand <Steven.Hand@xxxxxxxxxxxx>]

> On Tue, 2004-01-20 at 15:42, Jacob Gorm Hansen wrote:
> > On Tue, 2004-01-20 at 13:25, Steven Hand wrote:
> > > > On Tue, 2004-01-20 at 12:11, Jacob Gorm Hansen wrote:
> > > 
> > > Anyway, can you post -
> > > 
> > >   a) what it is you're trying to do in detail (I'm guessing it's 
> > >      to do with migration but not sure what stage you're at) and 
> 
> 
> This is my recovery function, which eip points to when the new domain is
> started:
> 
> static void recover(void)
> {
>     __cli();
>     HYPERVISOR_stack_switch(__KERNEL_DS, current->thread.esp0);
>     asm volatile("addl $0x0, -4(%%eax)" : :"eax"(current->thread.esp0));
>     while(1) HYPERVISOR_console_write("alive",5);
> 
>     ...
> 
> I touch the ring1 stack to make sure it is writeable (due to my
> migration hacks it may not always be).
> 
> The output on the serial looks like below. The first four lines are
> printed by my version of Xen as a response to SCHEDOP_exit:
> 
> exit dom 41 : esp1 c3a96000, ss 00000821
> eip c00b5b6d esp c3a95ed8  eflags 296
> Killing domain 41
> Releasing task 41
> DOM42: alive
> DOM42: alive
> DOM42: alive
> DOM42: alive
> DOM42: alive
> DOM42: alive
> DOM42: alive
> DOM42: alive
> DOM42: alive
> DOM42: alive
> DOM42: alive
> DOM42: alive
> DOM42: alive
> fault_in_hypervisor 2
> dom 42 : esp1 c3a96000, ss 00000821
> eip 00000000 esp c3a92004 eip 00000000  pf-addr c3a91ff8 eflags 10286
> Killing domain 42
> Releasing task 42
> 
> As you can see, the crash is not happening in direct response to some
> action in the domain, but rather as an effect of something happening
> outside. I was speculating that perhaps I need to re-register for the
> timer interrupt, or that the __cli() does not prevent Xen from trying to
> deliver them?

The __cli() should certainly prevent any events from being delivered. 

It's tricky to work out what the above means as you've clearly hacked 
Xen to e.g print "fault_in_hypervisor 2" (is 2 the error_code? is 
there any reason you've added this stuff in place of the regular code 
in do_trap() or do_page_fault()?). Can you post the code/diffs for 
these parts of xen? 

What is at 0xc3a91ff8? Have you actually taken a page fault? I note 
that zero eips are not so good -- but OTOH I don't know what those
values you print actually are [partic given there are two eips]... 
plus if we're really multiply faulting in the hypervisor, all bets
may well be off... 

cheers, 

S.