Re: [Xen-devel] [PATCH V3 2/2] xen: Introduce VM_EVENT_FLAG_SET_REGISTERS

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Mon, Sep 28, 2015 at 4:16 AM, Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx> wrote:

A previous version of this patch dealing with support for skipping
the current instruction when a vm_event response requested it
computed the instruction length in the hypervisor, adding non-trivial
code dependencies. This patch allows a userspace vm_event client to
simply request that the guest's EIP is set to an arbitary value,
computed by the introspection application. The registers that can
now be set are EAX-EDX, ESP, EBP, ESI, EDI, R8-R15, EFLAGS, and EIP.
CR0, CR3 and CR4 are not set, as at the time of vm_event_resume()
we can't call hvm_set_cr{0,3,4}() and simply setting
v->arch.hvm_vcpu.guest_cr[{0,3,4}] is unlikely to have the desired
effect. The rest of the vm_event registers are not set because
they're not being filled by hvm_event_fill_regs(), but only by
p2m_vm_event_fill_regs().
The VCPU needs to be paused for this flag to take effect.

Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>

Acked-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel