vfio: Fix MSI-X vector expansion

When new MSI-X vectors are enabled we need to disable MSI-X and
re-enable it with the correct number of vectors.  That means we need
to reprogram the eventfd triggers for each vector.  Prior to f4d45d47
vector->use tracked whether a vector was masked or unmasked and we
could always pick the KVM path when available for unmasked vectors.
Now vfio doesn't track mask state itself and vector->use and virq
remains configured even for masked vectors.  Therefore we need to ask
the MSI-X code whether a vector is masked in order to select the
correct signaling path.  As noted in the comment, MSI relies on
hardware to handle masking.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Cc: qemu-stable@nongnu.org # QEMU 2.1
vfio: Don't cache MSIMessage

Commit 40509f7f added a test to avoid updating KVM MSI routes when the
MSIMessage is unchanged and f4d45d47 switched to relying on this
rather than doing our own comparison.  Our cached msg is effectively
unused now.  Remove it.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
backends: Introduce chr-testdev

From: Paolo Bonzini <pbonzini@redhat.com>

chr-testdev enables a virtio serial channel to be used for guest
initiated qemu exits. hw/misc/debugexit already enables guest
initiated qemu exits, but only for PC targets. chr-testdev supports
any virtio-capable target. kvm-unit-tests/arm is already making use
of this backend.

Currently there is a single command implemented, "q".  It takes a
(prefix) argument for the exit code, thus an exit is implemented by
writing, e.g. "1q", to the virtio-serial port.

It can be used as:
   $QEMU ... \
     -device virtio-serial-device \
     -device virtserialport,chardev=ctd -chardev testdev,id=ctd

or, use:
   $QEMU ... \
     -device virtio-serial-device \
     -device virtconsole,chardev=ctd -chardev testdev,id=ctd

to bind it to virtio-serial port0.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
icount: put icount variables into TimerState.

This puts qemu_icount and qemu_icount_bias into TimerState structure to allow
them to be migrated.

Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
migration: migrate icount fields.

This fixes a bug where qemu_icount and qemu_icount_bias are not migrated.
It adds a subsection "timer/icount" to vmstate_timers so icount is migrated only
when needed.

Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
timer: add cpu_icount_to_ns function.

This adds cpu_icount_to_ns function which is needed for reverse execution.

It returns the time for a specific instruction.

Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
icount: Fix virtual clock start value on ARM

When using the icount option on ARM, the virtual
clock starts counting at realtime clock but it
should start at 0.

The reason why the virtual clock starts at realtime clock
is because the first time we call qemu_clock_warp (which
calls icount_warp_rt) in tcg_exec_all, qemu_icount_bias
(which is part of the virtual time computation mechanism)
will increment by realtime - vm_clock_warp_start, with
vm_clock_warp_start being 0 (see icount_warp_rt in cpus.c).

By changing the value of vm_clock_warp_start from 0 to -1,
the first time we call qemu_clock_warp which calls
icount_warp_rt, we will return immediatly because
icount_warp_rt first checks if vm_clock_warp_start is -1
and if it's the case it returns. Therefore, qemu_icount_bias
will first be incremented by the value of a virtual timer
deadline when the virtual cpu goes from active to inactive.

The virtual time will start at 0 and increment based
on the instruction counter when the vcpu is active or
the qemu_icount_bias value when inactive.

Signed-off-by: Sebastian Tanase <sebastian.tanase@openwide.fr>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
icount: Add QemuOpts for icount

Make icount parameter use QemuOpts style options in order
to easily add other suboptions.

Signed-off-by: Sebastian Tanase <sebastian.tanase@openwide.fr>
Tested-by: Camille Bégué <camille.begue@openwide.fr>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
icount: Add align option to icount

The align option is used for activating the align algorithm
in order to synchronise the host clock and the guest clock.

Signed-off-by: Sebastian Tanase <sebastian.tanase@openwide.fr>
Tested-by: Camille Bégué <camille.begue@openwide.fr>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
cpu-exec: Add sleeping algorithm

The goal is to sleep qemu whenever the guest clock
is in advance compared to the host clock (we use
the monotonic clocks). The amount of time to sleep
is calculated in the execution loop in cpu_exec.

At first, we tried to approximate at each for loop the real time elapsed
while searching for a TB (generating or retrieving from cache) and
executing it. We would then approximate the virtual time corresponding
to the number of virtual instructions executed. The difference between
these 2 values would allow us to know if the guest is in advance or delayed.
However, the function used for measuring the real time
(qemu_clock_get_ns(QEMU_CLOCK_REALTIME)) proved to be very expensive.
We had an added overhead of 13% of the total run time.

Therefore, we modified the algorithm and only take into account the
difference between the 2 clocks at the begining of the cpu_exec function.
During the for loop we try to reduce the advance of the guest only by
computing the virtual time elapsed and sleeping if necessary. The overhead
is thus reduced to 3%. Even though this method still has a noticeable
overhead, it no longer is a bottleneck in trying to achieve a better
guest frequency for which the guest clock is faster than the host one.

As for the the alignement of the 2 clocks, with the first algorithm
the guest clock was oscillating between -1 and 1ms compared to the host clock.
Using the second algorithm we notice that the guest is 5ms behind the host, which
is still acceptable for our use case.

The tests where conducted using fio and stress. The host machine in an i5 CPU at
3.10GHz running Debian Jessie (kernel 3.12). The guest machine is an arm versatile-pb
built with buildroot.

Currently, on our test machine, the lowest icount we can achieve that is suitable for
aligning the 2 clocks is 6. However, we observe that the IO tests (using fio) are
slower than the cpu tests (using stress).

Signed-off-by: Sebastian Tanase <sebastian.tanase@openwide.fr>
Tested-by: Camille Bégué <camille.begue@openwide.fr>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
cpu-exec: Print to console if the guest is late

If the align option is enabled, we print to the user whenever
the guest clock is behind the host clock in order for he/she
to have a hint about the actual performance. The maximum
print interval is 2s and we limit the number of messages to 100.
If desired, this can be changed in cpu-exec.c

Signed-off-by: Sebastian Tanase <sebastian.tanase@openwide.fr>
Tested-by: Camille Bégué <camille.begue@openwide.fr>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Merge remote-tracking branch 'remotes/awilliam/tags/vfio-pci-for-qemu-20140805.0' into staging

VFIO patches: Fix MSI-X vector expansion, remove MSI/X message caching

# gpg: Signature made Tue 05 Aug 2014 20:25:57 BST using RSA key ID 3BB08B22
# gpg: Can't check signature: public key not found

* remotes/awilliam/tags/vfio-pci-for-qemu-20140805.0:
  vfio: Don't cache MSIMessage
  vfio: Fix MSI-X vector expansion

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
monitor: Add drift info to 'info jit'

Show in 'info jit' the current delay between the host clock
and the guest clock. In addition, print the maximum advance
and delay of the guest compared to the host.

Signed-off-by: Sebastian Tanase <sebastian.tanase@openwide.fr>
Tested-by: Camille Bégué <camille.begue@openwide.fr>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
target-mips: Ignore unassigned accesses with KVM

MIPS registers an unassigned access handler which raises a guest bus
error exception. However this causes QEMU to crash when KVM is enabled
as it isn't called from the main execution loop so longjmp() gets called
without a corresponding setjmp().

Until the KVM API can be updated to trigger a guest exception in
response to an MMIO exit, prevent the bus error exception being raised
from mips_cpu_unassigned_access() if KVM is enabled.

The check is at run time since the do_unassigned_access callback is
initialised before it is known whether KVM will be enabled.

The problem can be triggered with Malta emulation by making the guest
write to the reset region at physical address 0x1bf00000, since it is
marked read-only which is treated as unassigned for writes.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Sanjay Lal <sanjayl@kymasys.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging

KVM changes include a MIPS patch and the testdev backend used by the
ARM kvm-unit-tests.  icount include the first part of reverse execution
and Sebastian Tanase's patches to slow down -icount execution to the
desired speed of the target.

v1->v2: fix dump_drift_info to print nothing outside icount mode,
        and to compile on 32-bit architectures

# gpg: Signature made Thu 07 Aug 2014 14:09:58 BST using RSA key ID 9B4D86F2
# gpg: Good signature from "Paolo Bonzini <pbonzini@redhat.com>"
# gpg:                 aka "Paolo Bonzini <bonzini@gnu.org>"

* remotes/bonzini/tags/for-upstream:
  target-mips: Ignore unassigned accesses with KVM
  monitor: Add drift info to 'info jit'
  cpu-exec: Print to console if the guest is late
  cpu-exec: Add sleeping algorithm
  icount: Add align option to icount
  icount: Add QemuOpts for icount
  icount: Fix virtual clock start value on ARM
  timer: add cpu_icount_to_ns function.
  migration: migrate icount fields.
  icount: put icount variables into TimerState.
  backends: Introduce chr-testdev

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>