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2014-01-17KVM: s390: enable Transactional ExecutionMichael Mueller
This patch enables transactional execution for KVM guests on s390 systems zec12 or later. We rework the allocation of the page containing the sie_block to also back the Interception Transaction Diagnostic Block. If available the TE facilities will be enabled. Setting bit 73 and 50 in vfacilities bitmask reveals the HW facilities Transactional Memory and Constraint Transactional Memory respectively to the KVM guest. Furthermore, the patch restores the Program-Interruption TDB from the Interception TDB in case a program interception has occurred and the ITDB has a valid format. Signed-off-by: Michael Mueller <mimu@linux.vnet.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
2013-09-24KVM: s390: Remove dead "rerun vcpu" codeThomas Huth
The need for SIE_INTERCEPT_RERUNVCPU has been removed long ago already, with the following commit: f7850c92884b40915001e332a0a33ed4f10158e8 [S390] remove kvm mmu reload on s390 Since the remainders are dead code, they are now removed by this patch. Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2013-06-20KVM: s390: Reworked LCTL and LCTLG instructionsThomas Huth
LCTL and LCTLG are also privileged instructions, thus there is no need for treating them separately from the other instructions in priv.c. So this patch moves these two instructions to priv.c, adds a check for supervisor state and simplifies the "handle_eb" instruction decoding by merging the two eb_handlers jump tables from intercept.c and priv.c into one table only. Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com> Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2013-05-21s390/kvm: Kick guests out of sie if prefix page host pte is touchedChristian Borntraeger
The guest prefix pages must be mapped writeable all the time while SIE is running, otherwise the guest might see random behaviour. (pinned at the pte level) Turns out that mlocking is not enough, the page table entry (not the page) might change or become r/o. This patch uses the gmap notifiers to kick guest cpus out of SIE. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-04-02KVM: s390: fix and enforce return code handling for irq injectionsHeiko Carstens
kvm_s390_inject_program_int() and friends may fail if no memory is available. This must be reported to the calling functions, so that this gets passed down to user space which should fix the situation. Alternatively we end up with guest state corruption. So fix this and enforce return value checking by adding a __must_check annotation to all of these function prototypes. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
2013-03-07s390/kvm,gaccess: add address space annotationsHeiko Carstens
Add missing address space annotations to all put_guest()/get_guest() callers. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-03-07s390/kvm,gaccess: shorten put/get_guest codeHeiko Carstens
The put_guest_u*/get_guest_u* are nothing but wrappers for the regular put_user/get_user uaccess functions. The only difference is that before accessing user space the guest address must be translated to a user space address. Change the order of arguments for the guest access functions so they match their uaccess parts. Also remove the u* suffix, so we simply have put_guest/get_guest which will automatically use the right size dependent on pointer type of the destination/source that now must be correct. In result the same behaviour as put_user/get_user except that accesses must be aligned. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-03-07s390/kvm: remove explicit -EFAULT return code checking on guest accessHeiko Carstens
Let's change to the paradigm that every return code from guest memory access functions that is not zero translates to -EFAULT and do not explictly compare. Explictly comparing the return value with -EFAULT has already shown to be a bit fragile. In addition this is closer to the handling of copy_to/from_user functions, which imho is in general a good idea. Also shorten the return code handling in interrupt.c a bit. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-01-07KVM: s390: Add support for channel I/O instructions.Cornelia Huck
Add a new capability, KVM_CAP_S390_CSS_SUPPORT, which will pass intercepts for channel I/O instructions to userspace. Only I/O instructions interacting with I/O interrupts need to be handled in-kernel: - TEST PENDING INTERRUPTION (tpi) dequeues and stores pending interrupts entirely in-kernel. - TEST SUBCHANNEL (tsch) dequeues pending interrupts in-kernel and exits via KVM_EXIT_S390_TSCH to userspace for subchannel- related processing. Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> Reviewed-by: Alexander Graf <agraf@suse.de> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-01-07KVM: s390: In-kernel handling of I/O instructions.Cornelia Huck
Explicitely catch all channel I/O related instructions intercepts in the kernel and set condition code 3 for them. This paves the way for properly handling these instructions later on. Note: This is not architecture compliant (the previous code wasn't either) since setting cc 3 is not the correct thing to do for some of these instructions. For Linux guests, however, it still has the intended effect of stopping css probing. Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> Reviewed-by: Alexander Graf <agraf@suse.de> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-01-07KVM: s390: Add support for machine checks.Cornelia Huck
Add support for injecting machine checks (only repressible conditions for now). This is a bit more involved than I/O interrupts, for these reasons: - Machine checks come in both floating and cpu varieties. - We don't have a bit for machine checks enabling, but have to use a roundabout approach with trapping PSW changing instructions and watching for opened machine checks. Reviewed-by: Alexander Graf <agraf@suse.de> Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-01-07KVM: s390: Decoding helper functions.Cornelia Huck
Introduce helper functions for decoding the various base/displacement instruction formats. Reviewed-by: Alexander Graf <agraf@suse.de> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2013-01-07KVM: s390: Constify intercept handler tables.Cornelia Huck
These tables are never modified. Reviewed-by: Alexander Graf <agraf@suse.de> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2012-07-26KVM: s390: Add implementation-specific trace eventsCornelia Huck
Introduce a new trace system, kvm-s390, for some kvm/s390 specific trace points: - injection of interrupts - delivery of interrupts to the guest - creation/destruction of kvm machines and vcpus - stop actions for vcpus - reset requests for userspace Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Avi Kivity <avi@redhat.com>
2012-07-26KVM: s390: Add architectural trace eventsCornelia Huck
Add trace events for several s390 architecture specifics: - SIE entry/exit - common intercepts - common instructions (sigp/diagnose) Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Avi Kivity <avi@redhat.com>
2012-07-20s390/comments: unify copyright messages and remove file namesHeiko Carstens
Remove the file name from the comment at top of many files. In most cases the file name was wrong anyway, so it's rather pointless. Also unify the IBM copyright statement. We did have a lot of sightly different statements and wanted to change them one after another whenever a file gets touched. However that never happened. Instead people start to take the old/"wrong" statements to use as a template for new files. So unify all of them in one go. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
2012-04-30KVM: s390: Handle sckpf instructionCornelia Huck
Handle the mandatory intercept SET CLOCK PROGRAMMABLE FIELD instruction. Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2012-03-08KVM: s390: do store status after handling STOP_ON_STOP bitJens Freimann
In handle_stop() handle the stop bit before doing the store status as described for "Stop and Store Status" in the Principles of Operation. We have to give up the local_int.lock before calling kvm store status since it calls gmap_fault() which might sleep. Since local_int.lock only protects local_int.* and not guest memory we can give up the lock. Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
2012-03-05KVM: s390: provide general purpose guest registers via kvm_runChristian Borntraeger
This patch adds the general purpose registers to the kvm_run structure. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
2011-11-17KVM: s390: Fix RUNNING flag misinterpretationCornelia Huck
CPUSTAT_RUNNING was implemented signifying that a vcpu is not stopped. This is not, however, what the architecture says: RUNNING should be set when the host is acting on the behalf of the guest operating system. CPUSTAT_RUNNING has been changed to be set in kvm_arch_vcpu_load() and to be unset in kvm_arch_vcpu_put(). For signifying stopped state of a vcpu, a host-controlled bit has been used and is set/unset basically on the reverse as the old CPUSTAT_RUNNING bit (including pushing it down into stop handling proper in handle_stop()). Cc: stable@kernel.org Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Avi Kivity <avi@redhat.com>
2011-07-24[S390] Use gmap translation for accessing guest memoryCarsten Otte
This patch removes kvm-s390 internal assumption of a linear mapping of guest address space to user space. Previously, guest memory was translated to user addresses using a fixed offset (gmsor). The new code uses gmap_fault to resolve guest addresses. Signed-off-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-07-24[S390] use gmap address spaces for kvm guest imagesCarsten Otte
This patch switches kvm from using (Qemu's) user address space to Martin's gmap address space. This way QEMU does not have to use a linker script in order to fit large guests at low addresses in its address space. Signed-off-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-07-24[S390] kvm: handle tprot interceptsChristian Borntraeger
When running a kvm guest we can get intercepts for tprot, if the host page table is read-only or not populated. This patch implements the most common case (linux memory detection). This also allows host copy on write for guest memory on newer systems. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2010-08-01KVM: s390: Fix build failure due to centralized vcpu locking patchesChristian Borntraeger
This patch fixes ERROR: "__kvm_s390_vcpu_store_status" [arch/s390/kvm/kvm.ko] undefined! triggered by commit 3268c56840dcee78c3e928336550f4e1861504c4 (kvm.git) Author: Avi Kivity <avi@redhat.com> Date: Thu May 13 12:21:46 2010 +0300 KVM: s390: Centrally lock arch specific vcpu ioctls Reported-by: Sachin Sant <sachinp@in.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Avi Kivity <avi@redhat.com>
2010-02-26[S390] Replace ENOTSUPP usage with EOPNOTSUPPHeiko Carstens
ENOTSUPP is not supposed to leak to userspace so lets just use EOPNOTSUPP everywhere. Doesn't fix a bug, but makes future reviews easier. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2010-01-25KVM: S390: fix potential array overrun in intercept handlingChristian Borntraeger
kvm_handle_sie_intercept uses a jump table to get the intercept handler for a SIE intercept. Static code analysis revealed a potential problem: the intercept_funcs jump table was defined to contain (0x48 >> 2) entries, but we only checked for code > 0x48 which would cause an off-by-one array overflow if code == 0x48. Use the compiler and ARRAY_SIZE to automatically set the limits. Cc: stable@kernel.org Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2009-09-10KVM: s390: streamline memslot handlingChristian Ehrhardt
This patch relocates the variables kvm-s390 uses to track guest mem addr/size. As discussed dropping the variables at struct kvm_arch level allows to use the common vcpu->request based mechanism to reload guest memory if e.g. changes via set_memory_region. The kick mechanism introduced in this series is used to ensure running vcpus leave guest state to catch the update. Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com> Signed-off-by: Avi Kivity <avi@redhat.com>
2009-09-10KVM: s390: infrastructure to kick vcpus out of guest stateChristian Ehrhardt
To ensure vcpu's come out of guest context in certain cases this patch adds a s390 specific way to kick them out of guest context. Currently it kicks them out to rerun the vcpu_run path in the s390 code, but the mechanism itself is expandable and with a new flag we could also add e.g. kicks to userspace etc. Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com> Signed-off-by: Avi Kivity <avi@redhat.com>
2009-06-10KVM: s390: Sanity check on validity interceptCarsten Otte
This patch adds a sanity check for the content of the guest prefix register content before faulting in the cpu lowcore that it refers to. The guest might end up in an endless loop where SIE complains about missing lowcore with incorrect content of the prefix register without this fix. Reported-by: Mijo Safradin <mijo@linux.vnet.ibm.com> Signed-off-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Christian Ehrhardt <ehrhardt@de.ibm.com> Signed-off-by: Avi Kivity <avi@redhat.com>
2009-03-24KVM: s390: Fix problem state check for b2 interceptsChristian Borntraeger
The kernel handles some priviledged instruction exits. While I was unable to trigger such an exit from guest userspace, the code should check for supervisor state before emulating a priviledged instruction. I also renamed kvm_s390_handle_priv to kvm_s390_handle_b2. After all there are non priviledged b2 instructions like stck (store clock). Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Avi Kivity <avi@redhat.com>
2008-07-27KVM: s390: Fix possible host kernel bug on lctl(g) handlingChristian Borntraeger
The lctl(g) instructions require a specific alignment for the parameters. The architecture requires a specification program check if these alignments are not used. Enforcing this alignment also removes a possible host BUG, since the get_guest functions check for proper alignment and emits a BUG. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-07-27KVM: s390: Fix instruction naming for lctlgChristian Borntraeger
Lets fix the name for the lctlg instruction... Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-05-07[S390] s390-kvm: leave sie context on work. Removes preemption requirementChristian Borntraeger
From: Martin Schwidefsky <schwidefsky@de.ibm.com> This patch fixes a bug with cpu bound guest on kvm-s390. Sometimes it was impossible to deliver a signal to a spinning guest. We used preemption as a circumvention. The preemption notifiers called vcpu_load, which checked for pending signals and triggered a host intercept. But even with preemption, a sigkill was not delivered immediately. This patch changes the low level host interrupt handler to check for the SIE instruction, if TIF_WORK is set. In that case we change the instruction pointer of the return PSW to rerun the vcpu_run loop. The kvm code sees an intercept reason 0 if that happens. This patch adds accounting for these types of intercept as well. The advantages: - works with and without preemption - signals are delivered immediately - much better host latencies without preemption Acked-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2008-04-27KVM: s390: intercepts for diagnose instructionsChristian Borntraeger
This patch introduces interpretation of some diagnose instruction intercepts. Diagnose is our classic architected way of doing a hypercall. This patch features the following diagnose codes: - vm storage size, that tells the guest about its memory layout - time slice end, which is used by the guest to indicate that it waits for a lock and thus cannot use up its time slice in a useful way - ipl functions, which a guest can use to reset and reboot itself In order to implement ipl functions, we also introduce an exit reason that causes userspace to perform various resets on the virtual machine. All resets are described in the principles of operation book, except KVM_S390_RESET_IPL which causes a reboot of the machine. Acked-by: Martin Schwidefsky <martin.schwidefsky@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-04-27KVM: s390: interprocessor communication via sigpChristian Borntraeger
This patch introduces in-kernel handling of _some_ sigp interprocessor signals (similar to ipi). kvm_s390_handle_sigp() decodes the sigp instruction and calls individual handlers depending on the operation requested: - sigp sense tries to retrieve information such as existence or running state of the remote cpu - sigp emergency sends an external interrupt to the remove cpu - sigp stop stops a remove cpu - sigp stop store status stops a remote cpu, and stores its entire internal state to the cpus lowcore - sigp set arch sets the architecture mode of the remote cpu. setting to ESAME (s390x 64bit) is accepted, setting to ESA/S390 (s390, 31 or 24 bit) is denied, all others are passed to userland - sigp set prefix sets the prefix register of a remote cpu For implementation of this, the stop intercept indication starts to get reused on purpose: a set of action bits defines what to do once a cpu gets stopped: ACTION_STOP_ON_STOP really stops the cpu when a stop intercept is recognized ACTION_STORE_ON_STOP stores the cpu status to lowcore when a stop intercept is recognized Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-04-27KVM: s390: intercepts for privileged instructionsChristian Borntraeger
This patch introduces in-kernel handling of some intercepts for privileged instructions: handle_set_prefix() sets the prefix register of the local cpu handle_store_prefix() stores the content of the prefix register to memory handle_store_cpu_address() stores the cpu number of the current cpu to memory handle_skey() just decrements the instruction address and retries handle_stsch() delivers condition code 3 "operation not supported" handle_chsc() same here handle_stfl() stores the facility list which contains the capabilities of the cpu handle_stidp() stores cpu type/model/revision and such handle_stsi() stores information about the system topology Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-04-27KVM: s390: interrupt subsystem, cpu timer, waitpswCarsten Otte
This patch contains the s390 interrupt subsystem (similar to in kernel apic) including timer interrupts (similar to in-kernel-pit) and enabled wait (similar to in kernel hlt). In order to achieve that, this patch also introduces intercept handling for instruction intercepts, and it implements load control instructions. This patch introduces an ioctl KVM_S390_INTERRUPT which is valid for both the vm file descriptors and the vcpu file descriptors. In case this ioctl is issued against a vm file descriptor, the interrupt is considered floating. Floating interrupts may be delivered to any virtual cpu in the configuration. The following interrupts are supported: SIGP STOP - interprocessor signal that stops a remote cpu SIGP SET PREFIX - interprocessor signal that sets the prefix register of a (stopped) remote cpu INT EMERGENCY - interprocessor interrupt, usually used to signal need_reshed and for smp_call_function() in the guest. PROGRAM INT - exception during program execution such as page fault, illegal instruction and friends RESTART - interprocessor signal that starts a stopped cpu INT VIRTIO - floating interrupt for virtio signalisation INT SERVICE - floating interrupt for signalisations from the system service processor struct kvm_s390_interrupt, which is submitted as ioctl parameter when injecting an interrupt, also carrys parameter data for interrupts along with the interrupt type. Interrupts on s390 usually have a state that represents the current operation, or identifies which device has caused the interruption on s390. kvm_s390_handle_wait() does handle waitpsw in two flavors: in case of a disabled wait (that is, disabled for interrupts), we exit to userspace. In case of an enabled wait we set up a timer that equals the cpu clock comparator value and sleep on a wait queue. [christian: change virtio interrupt to 0x2603] Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-04-27KVM: s390: sie intercept handlingChristian Borntraeger
This path introduces handling of sie intercepts in three flavors: Intercepts are either handled completely in-kernel by kvm_handle_sie_intercept(), or passed to userspace with corresponding data in struct kvm_run in case kvm_handle_sie_intercept() returns -ENOTSUPP. In case of partial execution in kernel with the need of userspace support, kvm_handle_sie_intercept() may choose to set up struct kvm_run and return -EREMOTE. The trivial intercept reasons are handled in this patch: handle_noop() just does nothing for intercepts that don't require our support at all handle_stop() is called when a cpu enters stopped state, and it drops out to userland after updating our vcpu state handle_validity() faults in the cpu lowcore if needed, or passes the request to userland Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Avi Kivity <avi@qumranet.com>