how to set up a #VE

[Big Strong <fangtuo90@gmail.com>]

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I want to set up an EPT page so as to trigger the #VE for testing purpose.
However, some problems are met.

As the Intel Manual said, there are many conditions to trigger a #VE:

a)      If an access to a guest-physical address causes an EPT violation, bit
63 (0) of exactly one of the EPT paging-structure entries used to translate
that address is used to determine *whether the EPT violation is convertible*:
either an entry that is not present (if the guest-physical address does not
translate to a physical address) or an entry that maps a page (if it does).

b)      A convertible EPT violation instead causes a virtualization
exception if the following all hold:

• CR0.PE = 1;

• the logical processor is not in the process of delivering an event
through the IDT; and

• the 32 bits at offset 4 in the virtualization-exception information area
are all 0.
In xc_altp2m.c <http://In xc_altp2m.c, there is a function
xc_altp2m_set_vcpu_enable_notify which is used to set up the #VE
information area. However, as the>, there is a function
xc_altp2m_set_vcpu_enable_notify which is used to set up the #VE
information area. However, as the arguments gfn is a physical address (of
the guest?), how can I safely assign an unused physical memory space to
store #VE info?

Besides, there is no xenctrl interface for setting the suprress_ve bit (63)
of the EPT PTE, which is needed to trigger #VE. Even though I can set that
with ept_set_entry function, this is an internal function of Xen and
unavailble to dom0.

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