KVM's "Lazy FPU loading" means that sometimes L0 needs to set CR0.TS, even
if a guest didn't set it. Moreover, L0 must also trap CR0.TS changes and
NM exceptions, even if we have a guest hypervisor (L1) who didn't want these
traps. And of course, conversely: If L1 wanted to trap these events, we
must let it, even if L0 is not interested in them.

This patch fixes some existing KVM code (in update_exception_bitmap(),
vmx_fpu_activate(), vmx_fpu_deactivate()) to do the correct merging of L0's
and L1's needs. Note that handle_cr() was already fixed in the above patch,
and that new code in introduced in previous patches already handles CR0
correctly (see prepare_vmcs02(), prepare_vmcs12(), and nested_vmx_vmexit()).
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

When L2 tries to modify CR0 or CR4 (with mov or clts), and modifies a bit
which L1 asked to shadow (via CR[04]_GUEST_HOST_MASK), we already do the right
thing: we let L1 handle the trap (see nested_vmx_exit_handled_cr() in a
previous patch).
When L2 modifies bits that L1 doesn't care about, we let it think (via
CR[04]_READ_SHADOW) that it did these modifications, while only changing
(in GUEST_CR[04]) the bits that L0 doesn't shadow.

This is needed for corect handling of CR0.TS for lazy FPU loading: L0 may
want to leave TS on, while pretending to allow the guest to change it.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This patch adds correct handling of IDT_VECTORING_INFO_FIELD for the nested
case.

When a guest exits while delivering an interrupt or exception, we get this
information in IDT_VECTORING_INFO_FIELD in the VMCS. When L2 exits to L1,
there's nothing we need to do, because L1 will see this field in vmcs12, and
handle it itself. However, when L2 exits and L0 handles the exit itself and
plans to return to L2, L0 must inject this event to L2.

In the normal non-nested case, the idt_vectoring_info case is discovered after
the exit, and the decision to inject (though not the injection itself) is made
at that point. However, in the nested case a decision of whether to return
to L2 or L1 also happens during the injection phase (see the previous
patches), so in the nested case we can only decide what to do about the
idt_vectoring_info right after the injection, i.e., in the beginning of
vmx_vcpu_run, which is the first time we know for sure if we're staying in
L2.

Therefore, when we exit L2 (is_guest_mode(vcpu)), we disable the regular
vmx_complete_interrupts() code which queues the idt_vectoring_info for
injection on next entry - because such injection would not be appropriate
if we will decide to exit to L1. Rather, we just save the idt_vectoring_info
and related fields in vmcs12 (which is a convenient place to save these
fields). On the next entry in vmx_vcpu_run (*after* the injection phase,
potentially exiting to L1 to inject an event requested by user space), if
we find ourselves in L1 we don't need to do anything with those values
we saved (as explained above). But if we find that we're in L2, or rather
*still* at L2 (it's not nested_run_pending, meaning that this is the first
round of L2 running after L1 having just launched it), we need to inject
the event saved in those fields - by writing the appropriate VMCS fields.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Similar to the previous patch, but concerning injection of exceptions rather
than external interrupts.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

The code in this patch correctly emulates external-interrupt injection
while a nested guest L2 is running.

Because of this code's relative un-obviousness, I include here a longer-than-
usual justification for what it does - much longer than the code itself ;-)

To understand how to correctly emulate interrupt injection while L2 is
running, let's look first at what we need to emulate: How would things look
like if the extra L0 hypervisor layer is removed, and instead of L0 injecting
an interrupt, we had hardware delivering an interrupt?

Now we have L1 running on bare metal with a guest L2, and the hardware
generates an interrupt. Assuming that L1 set PIN_BASED_EXT_INTR_MASK to 1, and
VM_EXIT_ACK_INTR_ON_EXIT to 0 (we'll revisit these assumptions below), what
happens now is this: The processor exits from L2 to L1, with an external-
interrupt exit reason but without an interrupt vector. L1 runs, with
interrupts disabled, and it doesn't yet know what the interrupt was. Soon
after, it enables interrupts and only at that moment, it gets the interrupt
from the processor. when L1 is KVM, Linux handles this interrupt.

Now we need exactly the same thing to happen when that L1->L2 system runs
on top of L0, instead of real hardware. This is how we do this:

When L0 wants to inject an interrupt, it needs to exit from L2 to L1, with
external-interrupt exit reason (with an invalid interrupt vector), and run L1.
Just like in the bare metal case, it likely can't deliver the interrupt to
L1 now because L1 is running with interrupts disabled, in which case it turns
on the interrupt window when running L1 after the exit. L1 will soon enable
interrupts, and at that point L0 will gain control again and inject the
interrupt to L1.

Finally, there is an extra complication in the code: when nested_run_pending,
we cannot return to L1 now, and must launch L2. We need to remember the
interrupt we wanted to inject (and not clear it now), and do it on the
next exit.

The above explanation shows that the relative strangeness of the nested
interrupt injection code in this patch, and the extra interrupt-window
exit incurred, are in fact necessary for accurate emulation, and are not
just an unoptimized implementation.

Let's revisit now the two assumptions made above:

If L1 turns off PIN_BASED_EXT_INTR_MASK (no hypervisor that I know
does, by the way), things are simple: L0 may inject the interrupt directly
to the L2 guest - using the normal code path that injects to any guest.
We support this case in the code below.

If L1 turns on VM_EXIT_ACK_INTR_ON_EXIT, things look very different from the
description above: L1 expects to see an exit from L2 with the interrupt vector
already filled in the exit information, and does not expect to be interrupted
again with this interrupt. The current code does not (yet) support this case,
so we do not allow the VM_EXIT_ACK_INTR_ON_EXIT exit-control to be turned on
by L1.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This patch contains the logic of whether an L2 exit should be handled by L0
and then L2 should be resumed, or whether L1 should be run to handle this
exit (using the nested_vmx_vmexit() function of the previous patch).

The basic idea is to let L1 handle the exit only if it actually asked to
trap this sort of event. For example, when L2 exits on a change to CR0,
we check L1's CR0_GUEST_HOST_MASK to see if L1 expressed interest in any
bit which changed; If it did, we exit to L1. But if it didn't it means that
it is we (L0) that wished to trap this event, so we handle it ourselves.

The next two patches add additional logic of what to do when an interrupt or
exception is injected: Does L0 need to do it, should we exit to L1 to do it,
or should we resume L2 and keep the exception to be injected later.

We keep a new flag, "nested_run_pending", which can override the decision of
which should run next, L1 or L2. nested_run_pending=1 means that we *must* run
L2 next, not L1. This is necessary in particular when L1 did a VMLAUNCH of L2
and therefore expects L2 to be run (and perhaps be injected with an event it
specified, etc.). Nested_run_pending is especially intended to avoid switching
to L1 in the injection decision-point described above.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This patch adds a bunch of tests of the validity of the vmcs12 fields,
according to what the VMX spec and our implementation allows. If fields
we cannot (or don't want to) honor are discovered, an entry failure is
emulated.

According to the spec, there are two types of entry failures: If the problem
was in vmcs12's host state or control fields, the VMLAUNCH instruction simply
fails. But a problem is found in the guest state, the behavior is more
similar to that of an exit.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This patch implements nested_vmx_vmexit(), called when the nested L2 guest
exits and we want to run its L1 parent and let it handle this exit.

Note that this will not necessarily be called on every L2 exit. L0 may decide
to handle a particular exit on its own, without L1's involvement; In that
case, L0 will handle the exit, and resume running L2, without running L1 and
without calling nested_vmx_vmexit(). The logic for deciding whether to handle
a particular exit in L1 or in L0, i.e., whether to call nested_vmx_vmexit(),
will appear in a separate patch below.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Before nested VMX support, the exit handler for a guest executing a VMX
instruction (vmclear, vmlaunch, vmptrld, vmptrst, vmread, vmread, vmresume,
vmwrite, vmon, vmoff), was handle_vmx_insn(). This handler simply threw a #UD
exception. Now that all these exit reasons are properly handled (and emulate
the respective VMX instruction), nothing calls this dummy handler and it can
be removed.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Implement the VMLAUNCH and VMRESUME instructions, allowing a guest
hypervisor to run its own guests.

This patch does not include some of the necessary validity checks on
vmcs12 fields before the entry. These will appear in a separate patch
below.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This patch contains code to prepare the VMCS which can be used to actually
run the L2 guest, vmcs02. prepare_vmcs02 appropriately merges the information
in vmcs12 (the vmcs that L1 built for L2) and in vmcs01 (our desires for our
own guests).
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Move some of the control field setup to common functions. These functions will
also be needed for running L2 guests - L0's desires (expressed in these
functions) will be appropriately merged with L1's desires.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Move the setting of constant host-state fields (fields that do not change
throughout the life of the guest) from vmx_vcpu_setup to a new common function
vmx_set_constant_host_state(). This function will also be used to set the
host state when running L2 guests.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Implement the VMREAD and VMWRITE instructions. With these instructions, L1
can read and write to the VMCS it is holding. The values are read or written
to the fields of the vmcs12 structure introduced in a previous patch.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This patch implements the VMPTRST instruction.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This patch implements the VMPTRLD instruction.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This patch implements the VMCLEAR instruction.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

VMX instructions specify success or failure by setting certain RFLAGS bits.
This patch contains common functions to do this, and they will be used in
the following patches which emulate the various VMX instructions.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

In this patch we add to vmcs12 (the VMCS that L1 keeps for L2) all the
standard VMCS fields.

Later patches will enable L1 to read and write these fields using VMREAD/
VMWRITE, and they will be used during a VMLAUNCH/VMRESUME in preparing vmcs02,
a hardware VMCS for running L2.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

We saw in a previous patch that L1 controls its L2 guest with a vcms12.
L0 needs to create a real VMCS for running L2. We call that "vmcs02".
A later patch will contain the code, prepare_vmcs02(), for filling the vmcs02
fields. This patch only contains code for allocating vmcs02.

In this version, prepare_vmcs02() sets *all* of vmcs02's fields each time we
enter from L1 to L2, so keeping just one vmcs02 for the vcpu is enough: It can
be reused even when L1 runs multiple L2 guests. However, in future versions
we'll probably want to add an optimization where vmcs02 fields that rarely
change will not be set each time. For that, we may want to keep around several
vmcs02s of L2 guests that have recently run, so that potentially we could run
these L2s again more quickly because less vmwrites to vmcs02 will be needed.

This patch adds to each vcpu a vmcs02 pool, vmx->nested.vmcs02_pool,
which remembers the vmcs02s last used to run up to VMCS02_POOL_SIZE L2s.
As explained above, in the current version we choose VMCS02_POOL_SIZE=1,
I.e., one vmcs02 is allocated (and loaded onto the processor), and it is
reused to enter any L2 guest. In the future, when prepare_vmcs02() is
optimized not to set all fields every time, VMCS02_POOL_SIZE should be
increased.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This patch includes a utility function for decoding pointer operands of VMX
instructions issued by L1 (a guest hypervisor)
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

When the guest can use VMX instructions (when the "nested" module option is
on), it should also be able to read and write VMX MSRs, e.g., to query about
VMX capabilities. This patch adds this support.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

An implementation of VMX needs to define a VMCS structure. This structure
is kept in guest memory, but is opaque to the guest (who can only read or
write it with VMX instructions).

This patch starts to define the VMCS structure which our nested VMX
implementation will present to L1. We call it "vmcs12", as it is the VMCS
that L1 keeps for its L2 guest. We will add more content to this structure
in later patches.

This patch also adds the notion (as required by the VMX spec) of L1's "current
VMCS", and finally includes utility functions for mapping the guest-allocated
VMCSs in host memory.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This patch allows the guest to enable the VMXE bit in CR4, which is a
prerequisite to running VMXON.

Whether to allow setting the VMXE bit now depends on the architecture (svm
or vmx), so its checking has moved to kvm_x86_ops->set_cr4(). This function
now returns an int: If kvm_x86_ops->set_cr4() returns 1, __kvm_set_cr4()
will also return 1, and this will cause kvm_set_cr4() will throw a #GP.

Turning on the VMXE bit is allowed only when the nested VMX feature is
enabled, and turning it off is forbidden after a vmxon.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This patch allows a guest to use the VMXON and VMXOFF instructions, and
emulates them accordingly. Basically this amounts to checking some
prerequisites, and then remembering whether the guest has enabled or disabled
VMX operation.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This patch adds to kvm_intel a module option "nested". This option controls
whether the guest can use VMX instructions, i.e., whether we allow nested
virtualization. A similar, but separate, option already exists for the
SVM module.

This option currently defaults to 0, meaning that nested VMX must be
explicitly enabled by giving nested=1. When nested VMX matures, the default
should probably be changed to enable nested VMX by default - just like
nested SVM is currently enabled by default.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

In VMX, before we bring down a CPU we must VMCLEAR all VMCSs loaded on it
because (at least in theory) the processor might not have written all of its
content back to memory. Since a patch from June 26, 2008, this is done using
a per-cpu "vcpus_on_cpu" linked list of vcpus loaded on each CPU.

The problem is that with nested VMX, we no longer have the concept of a
vcpu being loaded on a cpu: A vcpu has multiple VMCSs (one for L1, a pool for
L2s), and each of those may be have been last loaded on a different cpu.

So instead of linking the vcpus, we link the VMCSs, using a new structure
loaded_vmcs. This structure contains the VMCS, and the information pertaining
to its loading on a specific cpu (namely, the cpu number, and whether it
was already launched on this cpu once). In nested we will also use the same
structure to hold L2 VMCSs, and vmx->loaded_vmcs is a pointer to the
currently active VMCS.
Signed-off-by: NNadav Har'El <nyh@il.ibm.com>
Acked-by: NAcked-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

vmcs_readl() and friends are really short, but gcc thinks they are long because of
the out-of-line exception handlers.  Mark them always_inline to clear the
misunderstanding.
Signed-off-by: NAvi Kivity <avi@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

We clean up a failed VMREAD by clearing the output register.  Do
it in the exception handler instead of unconditionally.  This is
worthwhile since there are more than a hundred call sites.
Signed-off-by: NAvi Kivity <avi@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Only decache guest CR3 value if vcpu->arch.cr3 is stale.
Fixes loadvm with live guest.
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>
Tested-by: NMarkus Schade <markus.schade@gmail.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

Since the emulator now checks segment limits and access rights, it
generates a lot more accesses to the vmcs segment fields.  Undo some
of the performance hit by cacheing those fields in a read-only cache
(the entire cache is invalidated on any write, or on guest exit).
Signed-off-by: NAvi Kivity <avi@redhat.com>

Avoids a VMREAD.
Signed-off-by: NAvi Kivity <avi@redhat.com>

When doing a soft int, we need to bump eip before pushing it to
the stack.  Otherwise we'll do the int a second time.

[apw@canonical.com: merged eip update as per Jan's recommendation.]
Signed-off-by: NSerge E. Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: NAndy Whitcroft <apw@canonical.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

In case certain allocations fail, vmx_create_vcpu may return 0 as error
instead of a negative value encoded via ERR_PTR. This causes a NULL
pointer dereferencing later on in kvm_vm_ioctl_vcpu_create.
Reported-by: NSasha Levin <levinsasha928@gmail.com>
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

With TSC scaling in SVM the tsc-offset needs to be
calculated differently. This patch propagates this
calculation into the architecture specific modules so that
this complexity can be handled there.
Signed-off-by: NJoerg Roedel <joerg.roedel@amd.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

This patch implements a call-back into the architecture code
to allow the propagation of changes to the virtual tsc_khz
of the vcpu.
On SVM it updates the tsc_ratio variable, on VMX it does
nothing.
Signed-off-by: NJoerg Roedel <joerg.roedel@amd.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

This patch adds a callback into kvm_x86_ops so that svm and
vmx code can do intercept checks on emulated instructions.
Signed-off-by: NJoerg Roedel <joerg.roedel@amd.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

Use vmx_set_nmi_mask() instead of open-coding management of
the hardware bit and the software hint (nmi_known_unmasked).

There's a slight change of behaviour when running without
hardware virtual NMI support - we now clear the NMI mask if
NMI delivery faulted in that case as well.  This improves
emulation accuracy.
Signed-off-by: NAvi Kivity <avi@redhat.com>

vmx_complete_atomic_exit() cached it for us, so we can use it here.
Signed-off-by: NAvi Kivity <avi@redhat.com>

Only read it if we're going to use it later.
Signed-off-by: NAvi Kivity <avi@redhat.com>