This introduces the input and output handlers for 3270 device, setting
up the data tunnel among guest kernel, qemu and the 3270 client.
After the client connected and TN3270 handshake done, signal the not-ready
to ready status by an unsolicited device-end interrupt, and then the 3270
data stream could be handled correctly between the channel and socket.
Multiple commands generated by "Reset" key on x3270 are not supported now,
just simply terminate the connection.
Signed-off-by: Jing Liu <liujbjl@linux.vnet.ibm.com>
Signed-off-by: Yang Chen <bjcyang@linux.vnet.ibm.com>
Reviewed-by: QingFeng Hao <haoqf@linux.vnet.ibm.com>
Reviewed-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
This introduces a function named css_find_free_chpid() to find a
free channel path. Because virtio-ccw device used zero as its
channel path number, it would be sensible to skip the reserved one
and search upwards.
Signed-off-by: Jing Liu <liujbjl@linux.vnet.ibm.com>
Reviewed-by: QingFeng Hao <haoqf@linux.vnet.ibm.com>
Reviewed-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
The I/O adapters should exist as soon as the bus/infrastructure
exists, and not only when the guest is actually trying to do something
with them. While the lazy allocation was not wrong, allocating at init
time is cleaner, both for the architecture and the code. Let's adjust
this by having each device type (currently for PCI and virtio-ccw)
register the adapters for each ISC (as now we don't know which ISC the
guest will use) as soon as it initializes.
Use a two-dimensional array io_adapters[type][isc] to store adapters
in ChannelSubSys, so that we can conveniently get the adapter id by
the helper function css_get_adapter_id(type, isc).
Signed-off-by: Fei Li <sherrylf@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Let's use an enum for io adapter type, and standardize its naming to
CSS_IO_ADAPTER_* by changing S390_PCIPT_ADAPTER to CSS_IO_ADAPTER_PCI.
Signed-off-by: Fei Li <sherrylf@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Let's introduce a read-only property type that handles device ids of the
CssDevId type used for channel devices for future use. e.g. exposing the
busid of an I/O subchannel that is assigned to a ccw device.
Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
The subchannel is a means to access a device. While the device number is
assigned by the administrator, the subchannel number is assigned by
the channel subsystem in an ascending order on cold and hot plug.
When doing unplug and replug operations, the same device may end up on
a different subchannel; for example
- We start with a device fe.1.2222, which ends up at subchannel
fe.1.0000.
- Now we detach the device, attach a device fe.1.3333 (which would get
the now-free subchannel fe.1.0000), re-attach fe.1.2222 (which ends
up at subchannel fe.1.0001) and detach fe.1.3333.
- We now have the same device (fe.1.2222) available to the guest; it
just shows up on a different subchannel.
In such a case, the subchannel numbers are different from what a
QEMU would create during cold plug when parsing the command line.
As this would cause a guest visible change on migration, we do restore
the source system's value of the subchannel number on load.
So we are now fine from the guest perspective. From the host
perspective this will cause an inconsistent state in our internal data
structures, though.
For example, the subchannel 0 might not be at array position 0. This will
lead to problems when we continue doing hot (un/re) plug operations.
Let's fix this by cleaning up our internal data structures.
Reported-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
For TIC CCW, bit positions 8-32 of the format-1 CCW must contain zeros;
otherwise, a program-check condition is generated. For format-0 TIC CCWs,
bits 32-63 are ignored.
To convert TIC from format-0 CCW to format-1 CCW correctly, let's clear
bits 8-32 to guarantee compatibility.
Reviewed-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
According to the PoP, subchannels are only considered operational if
they are enabled _and_ the device number is valid. With the current
checks being enabled _or_ having a valid device number was
sufficient. This caused qemu to allow IO on subchannels that were not
enabled.
Fix the checks to require both bits to be set.
Signed-off-by: Sascha Silbe <silbe@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
The cssid 255 is reserved but still valid from an architectural
point of view. However, feeding a bogus schid of 0xffffffff into
the virtio hypercall will lead to a crash:
Stack trace of thread 138363:
#0 0x00000000100d168c css_find_subch (qemu-system-s390x)
#1 0x00000000100d3290 virtio_ccw_hcall_notify
#2 0x00000000100cbf60 s390_virtio_hypercall
#3 0x000000001010ff7a handle_hypercall
#4 0x0000000010079ed4 kvm_cpu_exec (qemu-system-s390x)
#5 0x00000000100609b4 qemu_kvm_cpu_thread_fn
#6 0x000003ff8b887bb4 start_thread (libpthread.so.0)
#7 0x000003ff8b78df0a thread_start (libc.so.6)
This is because the css array was only allocated for 0..254
instead of 0..255.
Let's fix this by bumping MAX_CSSID to 255 and fencing off the
reserved cssid of 255 during css image allocation.
Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
It's not obvious from the code flow that sch_handle_start_func() gets
called for rsch. Add some comments explaining this.
Signed-off-by: Sascha Silbe <silbe@linux.vnet.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
The CCW Format (F) flag of the Subchannel-Status Word (SCSW) indicates
the format of the CCWs "associated with an I/O operation", i.e. the
value of CCW-Format Control (F) bit of the Operation-Request Block
(ORB).
Copy the CCW format bit from the ORB to the SCSW so we correctly
indicate the format of the CCWs to the guest.
Signed-off-by: Sascha Silbe <silbe@linux.vnet.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Tracked down with an ugly, brittle and probably buggy Perl script.
Also move includes converted to <...> up so they get included before
ours where that's obviously okay.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
A lot of what virtio_ccw_device_realize() does isn't specific to
virtio; it would apply to emulated CCW as well. Factor it out to make
it easier to implement emulated CCW devices later on.
Signed-off-by: Sascha Silbe <silbe@linux.vnet.ibm.com>
Reviewed-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Let's introduce a CssDevId to handle device ids of the xx.x.xxxx
type used for channel devices. This has some benefits:
- We can use them in virtio-ccw and split the validity checks for
a channel device id in general from the constraint checking
within the virtio-ccw scope.
- We can reuse the device id type for future non-virtio channel
devices.
While we're at it, improve the validity checks and disallow e.g.
trailing characters.
Suggested-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Acked-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
According to the Principles of Operation (more precisely the subsection
'Channel-Report Word'), a subchannel put into the installed parameters
initialized state is in the same state as after an I/O system reset (just
parameters possibly changed). This implies that any I/O interrupts for that
subchannel are no longer pending (as I/O system resets clear I/O
interrupts). Therefore, we need an interface to clear pending I/O
interrupts. Make css_generate_sch_crws clear the pending IO interrupts for
the subchannel.
Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Move cpu_inject_* to the only C file where they are used.
Move ioinst.h declarations that need S390CPU to cpu.h, to make
ioinst.h independent of cpu.h.
Move channel declarations that only need SubchDev from cpu.h
to css.h, to make more channel users independent of cpu.h.
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
We must not allow a channel program to suspend if the suspend
control bit in the orb had not been specified.
Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
machine_init() will be gone, but we don't need it if we just
initialize the channel_subsys fields statically.
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Alexander Graf <agraf@suse.de>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <1455656347-29033-4-git-send-email-ehabkost@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
[adapted on top of indicator changes]
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
There's no need to use g_malloc0() to allocate the channel_subsys
struct, just use a static variable.
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Alexander Graf <agraf@suse.de>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <1455656347-29033-3-git-send-email-ehabkost@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
[adapted on top of indicator changes]
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Currently, virtio-ccw uses its own interfaces to keep indicators mapped
just once even if the same address has been registered multiple times.
These interfaces fit the PCI use case as well. Therefore, move them to
css and make them generic interfaces.
Signed-off-by: Yi Min Zhao <zyimin@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Clean up includes so that osdep.h is included first and headers
which it implies are not included manually.
This commit was created with scripts/clean-includes.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Message-id: 1453832250-766-8-git-send-email-peter.maydell@linaro.org
From the beginning, css support contained an error in csch handling:
instead of setting the clear bit in the function control bits twice, we
need to set the clear pending bit in the activity control bits. Let's
fix this.
Cc: qemu-stable@nongnu.org
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Only one channel report word (crw) may be pending if there is
event-information pending.
This patch introduces a bool-type field 'sei_pending' for the
channel subsystem, which indicates whether there are pending events.
It is set when event information is made pending and the crw
generated, and cleared after the guest has collected all pending
event information. A crw is not generated if this flag had already
been set.
Signed-off-by: Song Shan Gong <gongss@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
The "return;" statements at the end of functions do not make
much sense, so let's remove them.
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Alexander Graf <agraf@suse.de>
Cc: Richard Henderson <rth@twiddle.net>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
We keep the device's sense data in a byte array (following the
architecture), but the ecws are an array of 32 bit values. If we
just blindly copy the values, the sense data will change from
de-facto BE data to de-facto cpu-endian data, which means we end
up doing an incorrect conversion on LE hosts.
Let's just explicitly convert to cpu-endianness while assembling
the irb.
Reported-by: Andy Lutomirski <luto@kernel.org>
Tested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
When executing the start function, we should start with a clear state
regarding subchannel and device status; it is easy to forget updating one
of them after the ccw has been processed.
Note that we don't need to care about resetting the various control
fields: They are cleared by tsch(), and if they were still pending,
we wouldn't be able to execute the start function in the first
place.
Also note that we don't want to clear cstat/dstat if a suspended
subchannel is resumed.
This fixes a bug where we would continue to present channel-program
check in cstat even though later ccw requests for the subchannel
finished without error (i.e. cstat should be 0).
Cc: qemu-stable@nongnu.org
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Type-0 ccws need to have a count > 0 for any command other than TIC.
Generate a channel-program check if this is not the case.
Reviewed-by: Matthew Rosato <mjrosato@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
In CCW-0 format TIC command 4 highest bits are ignored in the subchannel.
In CCW-1 format the TIC command 4 highest bits must be 0.
To convert TIC from CCW-0 to CCW-1 we clear the 4 highest bits
to guarantee compatibility.
Signed-off-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
We need a possibility to run code when a subchannel gets disabled.
This patch adds the necessary infrastructure.
Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Our main channel_subsys structure is not a device (yet), but we need
to setup mss/mcss-e again if the guest had enabled it before. Use
a hack that should catch most configurations (assuming that the guest
will have enabled at least one device in higher subchannel sets or
channel subsystems if it enabled the functionality.)
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Switch all the uses of ld/st*_phys to address_space_ld/st*,
except for those cases where the address space is the CPU's
(ie cs->as). This was done with the following script which
generates a Coccinelle patch.
A few over-80-columns lines in the result were rewrapped by
hand where Coccinelle failed to do the wrapping automatically,
as well as one location where it didn't put a line-continuation
'\' when wrapping lines on a change made to a match inside
a macro definition.
===begin===
#!/bin/sh -e
# Usage:
# ./ldst-phys.spatch.sh > ldst-phys.spatch
# spatch -sp_file ldst-phys.spatch -dir . | sed -e '/^+/s/\t/ /g' > out.patch
# patch -p1 < out.patch
for FN in ub uw_le uw_be l_le l_be q_le q_be uw l q; do
cat <<EOF
@ cpu_matches_ld_${FN} @
expression E1,E2;
identifier as;
@@
ld${FN}_phys(E1->as,E2)
@ other_matches_ld_${FN} depends on !cpu_matches_ld_${FN} @
expression E1,E2;
@@
-ld${FN}_phys(E1,E2)
+address_space_ld${FN}(E1,E2, MEMTXATTRS_UNSPECIFIED, NULL)
EOF
done
for FN in b w_le w_be l_le l_be q_le q_be w l q; do
cat <<EOF
@ cpu_matches_st_${FN} @
expression E1,E2,E3;
identifier as;
@@
st${FN}_phys(E1->as,E2,E3)
@ other_matches_st_${FN} depends on !cpu_matches_st_${FN} @
expression E1,E2,E3;
@@
-st${FN}_phys(E1,E2,E3)
+address_space_st${FN}(E1,E2,E3, MEMTXATTRS_UNSPECIFIED, NULL)
EOF
done
===endit===
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Change the handler for STCRW to use the new logical memory access
functions. Since STCRW is suppressed on protection/access exceptions,
we also have to make sure to re-queue the CRW in case it could not be
written to the memory.
Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Change the TSCH handler to use the new logical memory access functions.
Since the channel should not be updated in case of a protection or access
exception while writing to the guest memory, the css_do_tsch() has to be
split up into two parts, one for retrieving the IRB and one for the update.
Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
The schib parameter of css_do_msch() can be declared as const to
make it clear that it does not get modified by this function.
Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
This patch implements a pci bus for s390x together with infrastructure
to generate and handle hotplug events, to configure/unconfigure via
sclp instruction, to do iommu translations and provide s390 support for
MSI/MSI-X notification processing.
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
We must not allow chains of more than 255 ccws without data transfer.
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Add support for format-0 ccws in channel programs. As a format-1 ccw
contains the same information as format-0 ccws, only supporting larger
addresses, simply convert every ccw to format-1 as we walk the chain.
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
We neglected to update the the channel-program-address field of the scsw
after completion of the start or the halt function: Fortunately, Linux
didn't miss it so far. Let's update it for the cases where the cpa is
expected to be valid; in some cases, the cpa is 'unpredictable', so we
leave it untouched.
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Remove the need for a cpu to inject a floating interrupt on kvm.
Acked-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
This patch adds live migration support for virtio-ccw devices.
It's not done with vmstate because virtio itself is not yet ported
to vmstate either.
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
We should not try to store the emw portion of the irb if extended
measurements are not applicable. In particular, we should not surprise
the guest by storing a larger irb if it did not enable extended
measurements.
Cc: qemu-stable@nongnu.org
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Register an I/O adapter interrupt source for when virtio-ccw devices start
using adapter interrupts.
Reviewed-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Current css code saves the operation request block (orb) in the
subchannel structure for later consumption by the start function
handler. This might make sense for asynchronous execution of the
start function (which qemu doesn't support), but not in our case;
it would even be wrong since orb contains a reference to a local
variable in the base ssch handler.
Let's just pass the orb through the start function call chain for
ssch; for rsch, we can pass NULL as the backend function does not
use any information passed via the orb there.
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Handle the new CCW_CMD_SET_IND_ADAPTER command enabling adapter interrupts
on guest request. When active, host->guest notifications will be handled
via global_indicator -> queue indicators instead of queue indicators +
subchannel I/O interrupt. Indicators for virtqueues may be present at an
offset.
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Most typos were found using a modified version of codespell:
accross -> across
issueing -> issuing
TICNT_THRESHHOLD -> TICNT_THRESHOLD
bandwith -> bandwidth
VCARD_7816_PROPIETARY -> VCARD_7816_PROPRIETARY
occured -> occurred
gaurantee -> guarantee
sofware -> software
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
On hosts that support ioeventfd, make use of it for host-to-guest
notifications via diagnose 500.
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Jing Liu