Messages in this thread | | | Subject | Re: [PATCH v4 0/7] vfio: ap: AP Queue Interrupt Control | From | Pierre Morel <> | Date | Fri, 1 Mar 2019 10:40:46 +0100 |
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On 28/02/2019 16:08, Halil Pasic wrote: > On Fri, 22 Feb 2019 16:29:53 +0100 > Pierre Morel <pmorel@linux.ibm.com> wrote: > >> This patch implement PQAP/AQIC interception in KVM. >> >> To implement this we need to add a new structure, vfio_ap_queue,to be >> able to retrieve the mediated device associated with a queue and specific >> values needed to register/unregister the interrupt structures: >> - APQN: to be able to issue the commands and search for queue structures >> - NIB : to unpin the NIB on clear IRQ >> - ISC : to unregister with the GIB interface >> - MATRIX: a pointer to the matrix mediated device >> - LIST: the list_head to handle the vfio_queue life cycle >> >> Having this structure and the list management greatly ease the handling >> of the AP queues and diminues the LOCs needed in the vfio_ap driver by >> more than 150 lines in comparison with the previous version. >> >> >> 0) Queues life cycle >> >> vfio_ap_queues are created on probe >> >> We define one bucket on the matrix device to store the free vfio_ap_queues, >> the queues not assign to any matrix mediated device. >> >> We define one bucket on each matrix mediated device to hold the >> vfio_ap_queues belonging to it. >> >> vfio_ap_queues are deleted on remove >> >> This makes the search for a queue easy and the detection of assignent >> incoherency obvious (the queue is not avilable) and simplifies assignment. >> >> >> 1) Phase 1, probe and remove from vfio_ap_queue >> >> The vfio_ap_queue structures are dynamically allocated and setup >> when a queue is probed by the ap_vfio_driver. >> The vfio_ap_queue is linked to the ap_queue device as the driver data. >> >> The new The vfio_ap_queue is put on a free_list belonging to the >> matrix device. >> >> The vfio_ap_queue are free during remove. >> >> >> 2) Phase 2, assignment of vfio_ap_queue to a mediated device >> >> When a APID is assigned we look for APQI already assigned to >> the matrix mediated device and associate all the queue with the >> APQN = (APID,APQI) to the mediated device by adding them to >> the mediated device queue list. >> We do the same when a APQI is assigned. >> >> If any queue with a matching APQN can not be found on the matrix >> device free list it means it is already associated to another matrix >> mediated device and no queue is added to the matrix mediated device. >> >> 3) Phase 3, starting the guest >> >> When the VFIO device is opened the PQAP callback and a pointer to >> the matrix mediated device are set inside KVM during the open callback. >> >> When the device is closed or if a queue is removed, the vfio_ap_queue is >> dissociated from the mediated device. >> >> >> 4) Phase 3 intercepting the PQAP/AQIC instruction >> >> On interception of the PQAP/AQIC instruction, the interception code >> makes sure the pqap_hook is initialized and allowed to be called >> and call it. >> Otherwise it reports the usual -EOPNOTSUPP return code to let >> QEMU handle the fault. >> >> the pqap callback search for the queue asociated with the APQN >> stored in the register 0, setting the code to "illegal APQN" >> if the vfio_ap_queue can not be found. >> >> Depending on the "i" bit of the register 1, the pqap callback >> setup or clear the interruption by calling the host format PQAP/AQIC >> instruction. >> When seting up the interruption it uses the NIB and the guest ISC >> provided by the guest and the host ISC provided by the registration >> to the GIB code, pin the NIB and also stores ISC and NIB inside >> the vfio_ap_queue structure. >> When clearing the interrupt it retrieves the host ISC to unregister >> with the GIB code and unpin the NIB. >> >> We take care when enabling GISA that the guest may have issued a >> reset and will not need to disable the interuptions before >> re-enabling interruptions. > > Please let us know what guarantees, that we will disable the > interruptions we previously enabled using AQIC (and generally facilitate > proper cleanup) *before* kvm_s390_gisa_destroy() makes the gisa and > with that the IPM go away! > > Please note that IMHO this needs to be guaranteed by the kernel > regardless of what userspace (QEMU) or the guest does. > > (I've asked this question before during our internal review but I could > not find the answer if there was one after going trough my mails.) > > Regards, > Halil >
You are right. I will investigate this too.
Regards, Pierre
-- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany
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