EIP, xc_domain_hvm_getcontext_partial() and page fault events

EIP, xc_domain_hvm_getcontext_partial() and page fault events

[Razvan Cojocaru]

Hello,

I'm using page fault mem_events from dom0 userspace. When I receive one 
such mem_event, I'm retrieving register values for the VCPU that has 
caused it, using xc_domain_hvm_getcontext_partial().

At the same time, I'm printing out v->arch.user_regs.eip from 
p2m_mem_access_check() in arch/x86/mm/p2m.c, and I'm noticing that the 
EIP value I'm getting from xc_domain_hvm_getcontext_partial() is less 
than the EIP value stored in v->arch.user_regs.eip. This, I assume, can 
be explained by the fact that in p2m_mem_access_check() EIP points to 
the instruction _after_ the instruction that caused the page fault, and 
it's being rewound by the time I query it from dom0 userspace.

Now, what I am after is a way to get the "proper", rewound, EIP (and the 
rest of the registers from when EIP was _before_ the fault instruction) 
in p2m_mem_access_check(). Is there a way to achieve this?


Thanks,
Razvan Cojocaru