linux-kernel - Re: [PATCH v9 00/21] KVM: s390: enable zPCI for interpretive execution

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Date:   Tue, 28 Jun 2022 09:40:01 -0400
From:   Matthew Rosato <mjrosato@...ux.ibm.com>
To:     Christian Borntraeger <borntraeger@...ux.ibm.com>,
        linux-s390@...r.kernel.org
Cc:     alex.williamson@...hat.com, cohuck@...hat.com,
        schnelle@...ux.ibm.com, farman@...ux.ibm.com, pmorel@...ux.ibm.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com,
        gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com,
        svens@...ux.ibm.com, frankja@...ux.ibm.com, david@...hat.com,
        imbrenda@...ux.ibm.com, vneethv@...ux.ibm.com,
        oberpar@...ux.ibm.com, freude@...ux.ibm.com, thuth@...hat.com,
        pasic@...ux.ibm.com, pbonzini@...hat.com, corbet@....net,
        jgg@...dia.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v9 00/21] KVM: s390: enable zPCI for interpretive
 execution

On 6/28/22 8:35 AM, Christian Borntraeger wrote:
> Am 27.06.22 um 22:57 schrieb Matthew Rosato:
>> On 6/6/22 4:33 PM, Matthew Rosato wrote:
>>> Enable interpretive execution of zPCI instructions + adapter 
>>> interruption
>>> forwarding for s390x KVM vfio-pci.  This is done by triggering a routine
>>> when the VFIO group is associated with the KVM guest, transmitting to
>>> firmware a special token (GISA designation) to enable that specific 
>>> guest
>>> for interpretive execution on that zPCI device.  Load/store 
>>> interpreation
>>> enablement is then controlled by userspace (based upon whether or not a
>>> SHM bit is placed in the virtual function handle).  Adapter Event
>>> Notification interpretation is controlled from userspace via a new KVM
>>> ioctl.
>>>
>>> By allowing intepretation of zPCI instructions and firmware delivery of
>>> interrupts to guests, we can reduce the frequency of guest SIE exits for
>>> zPCI.
>>>
>>>  From the perspective of guest configuration, you passthrough zPCI 
>>> devices
>>> in the same manner as before, with intepretation support being used by
>>> default if available in kernel+qemu.
>>>
>>> Will follow up with a link the most recent QEMU series.
>>>
>>> Changelog v8->v9:
>>> - Rebase on top of 5.19-rc1, adjust ioctl and capability defines
>>> - s/kzdev = 0/kzdev = NULL/ (Alex)
>>> - rename vfio_pci_zdev_open to vfio_pci_zdev_open_device (Jason)
>>> - rename vfio_pci_zdev_release to vfio_pci_zdev_close_device (Jason)
>>> - make vfio_pci_zdev_close_device return void, instead WARN_ON or ignore
>>>    errors in lower level function (kvm_s390_pci_unregister_kvm) (Jason)
>>> - remove notifier accidentally left in struct zpci_dev + associated
>>>    include statment (Jason)
>>> - Remove patch 'KVM: s390: introduce CPU feature for zPCI 
>>> Interpretation'
>>>    based on discussion in QEMU thread.
>>>
>>
>> Ping -- I'm hoping this can make the next merge window, but there are 
>> still 2 patches left without any review tag (16 & 17).
> 
> Yes, I will queue this (as is). Ideally you would rebase this on top of 
> kvm/next but I can also do while applying.
> Let me know if you want to respin with the Nits from Pierre.

Ah, sorry -- I assume you mean Paolo's kvm/next?  I tried now and see 
some conflicts with the ioctl patch.

Why don't I rebase on top of kvm/next along with these couple of changes 
from Pierre and send this as a v10 for you to queue.

While at it, there's one other issue to be aware of -- There will also 
be small merge conflicts with a patch that just hit vfio-next, "vfio: 
de-extern-ify function prototypes" - My series already avoids adding 
externs to new prototypes, but adjacent code changes will cause a 
conflict with patches 10 and 17.

Not sure what the best way to proceed there is.

https://lore.kernel.org/kvm/165471414407.203056.474032786990662279.stgit@omen/