Currently there is a subop for setting the memaccess of a page, but not
for consulting it. The new HVMOP_altp2m_get_mem_access adds this
functionality.
Both altp2m get/set mem access functions use the struct
xen_hvm_altp2m_mem_access which has now dropped the `set' part and has
been renamed from xen_hvm_altp2m_set_mem_access.
Signed-off-by: Adrian Pop <apop@bitdefender.com>
Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>
In a classic HVI + Xen setup, the introspection engine would monitor
legacy guest page-tables by marking them read-only inside the EPT; this
way any modification explicitly made by the guest or implicitly made by
the CPU page walker would trigger an EPT violation, which would be
forwarded by Xen to the SVA and thus the HVI agent. The HVI agent would
analyse the modification, and act upon it - for example, a virtual page
may be remapped (its guest physical address changed inside the
page-table), in which case the introspection logic would update the
protection accordingly (remove EPT hook on the old gpa, and place a new
EPT hook on the new gpa). In other cases, the modification may be of no
interest to the introspection engine - for example, the accessed/dirty
bits may be cleared by the operating system or the accessed/dirty bits
may be set by the CPU page walker.
In our tests we discovered that the vast majority of guest page-table
modifications fall in the second category (especially on Windows 10 RS4
x64 - more than 95% of ALL the page-table modifications are irrelevant to
us) - they are of no interest to the introspection logic, but they
trigger a very costly EPT violation nonetheless. Therefore, we decided
to make use of the new #VE & VMFUNC features in recent Intel CPUs to
accelerate the guest page-tables monitoring in the following way:
1. Each monitored page-table would be flagged as being convertible
inside the EPT, thus enabling the CPU to deliver a virtualization
exception to he guest instead of generating a traditional EPT
violation.
2. We inject a small filtering driver inside the protected guest VM,
which would intercept the virtualization exception in order to handle
guest page-table modifications.
3. We create a dedicated EPT view (altp2m) for the in-guest agent, which
would isolate the agent from the rest of the operating system; the
agent will switch in and out of the protected EPT view via the VMFUNC
instruction placed inside a trampoline page, thus making the agent
immune to malicious code inside the guest.
This way, all the page-table accesses would generate a
virtualization-exception inside the guest instead of a costly EPT
violation; the #VE agent would emulate and analyse the modification, and
decide whether it is relevant for the main introspection logic; if it is
relevant, it would do a VMCALL and notify the introspection engine
about the modification; otherwise, it would resume normal instruction
execution, thus avoiding a very costly VM exit.
Signed-off-by: Adrian Pop <apop@bitdefender.com>
Reviewed-by: Tamas K Lengyel <tamas@tklengyel.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Introduce a new hvmop, HVMOP_altp2m_set_suppress_ve, which allows a
domain to change the value of the #VE suppress bit for a page.
Add a libxc wrapper for invoking this hvmop.
Signed-off-by: Adrian Pop <apop@bitdefender.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com>
For the default EPT view we have xc_set_mem_access_multi(), which
is able to set an array of pages to an array of access rights with
a single hypercall. However, this functionality was lacking for the
altp2m subsystem, which could only set page restrictions for one
page at a time. This patch addresses the gap.
HVMOP_altp2m_set_mem_access_multi has been added as a HVMOP (as opposed to a
DOMCTL) for consistency with its HVMOP_altp2m_set_mem_access counterpart (and
hence with the original altp2m design, where domains are allowed - with the
proper altp2m access rights - to alter these settings), in the absence of an
official position on the issue from the original altp2m designers.
Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
Signed-off-by: Petre Pircalabu <ppircalabu@bitdefender.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>
Mixed throughout libxc are uint32_t, int, and domid_t for domid parameters.
With a signed type, and an explicitly 16-bit type, it is exceedingly difficult
to construct an INVALID_DOMID constant which works with all of them. (The
main problem being that domid_t gets unconditionally zero extended when
promoted to int for arithmatic.)
Libxl uses uint32_t consistently everywhere, so alter libxc to match.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Release-acked-by: Julien Grall <julien.grall@linaro.org>
[ wei: fix compilation error in libxl ]
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
libxencall will provide a stable API and ABI for calling hypercalls
(although those hypercalls themselves may not have a stable API). As
well as the hypercall buffer infrastructure needed in order to safely
provide pointer arguments to hypercalls.
libxenctrl encapsulates a instance of this interface, so users of that
library are not currently subjected to any actual changes. However all
hypercalls made internally by libxc now use the correct interface. It
is expected that most users of this library will be other libraries
providing a higher level interface, rather than applications directly.
Only the basic functionality to allocate hypercall safe memory is
moved, the type safe stuff and bounce buffers remain in libxc.
Note that the functionality to map foreign pages using privcmd is not
yet moved, meaning that an xc_interface will now contain two open
privcmd file descriptors. Foreign memory mapping is logically separate
functionality and will be moved into its own library.
The new library uses a version script to ensure that only expected
symbols are exported and to version them such that ABI guarantees can
be kept in the future.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
[ ijc -- updated MINIOS_UPSTREAM_REVISION and QEMU_TRADITIONAL_REVISION ]
As recommended in http://www.gnu.org/licenses/gpl-howto.en.html.
This is the result of:
$ git grep -El Mass\|Temple\|Franklin | xargs ./fsf.pl
Where fsf.pl is:
#!/usr/bin/perl -w -pi.bak -0777
my $repl = 'If not, see <http://www.gnu.org/licenses/>.';
my $br = qr/(?:\s*\n\s*(?:[\*\#]|\/\/|\.\\" )?\s*|\s+)/;
my $inwt = qr/[Ii]f${br}not,${br}write${br}(?:to${br})?the${br}Free${br}Software${br}Foundation,(?:${br}Inc\.,)?/;
my $mass = qr/675${br}Mass${br}Ave,?${br}Cambridge,?${br}MA${br}02139,?${br}USA,?\.?/;
my $franklin = qr/51${br}Franklin${br}St(?:reet)?(?:,${br}| - )Fifth${br}Floor,?${br}Boston,?${br}MA,?${br}02110-1301,?${br}USA,?\.?/;
my $temple = qr/59${br}Temple${br}Place(?:,${br}| - )Suite${br}330,?${br}Boston,?${br}MA,?${br}021110?-1307,?${br}USA,?\.?/;
s|$inwt$br$mass|$repl|m;
s|$inwt$br$franklin|$repl|m;
s|$inwt$br$temple|$repl|m;
The only remaining mentions of these addresses are in COPYING files which I
haven't touched.
Some of the changed files are imports from elsewhere, however
filtering them out is tricky, I think it is tolerable to have these
files be modified here and then perhaps reverted on the next sync,
since it's only 1-2 lines and obvious what is going on.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Razvan Cojocaru
Adrian Pop
Andrew Cooper
Ian Campbell
Tamas K Lengyel