From: Cornelia Huck <cohuck@redhat.com>
To: Matthew Rosato <mjrosato@linux.ibm.com>, linux-s390@vger.kernel.org
Cc: alex.williamson@redhat.com, schnelle@linux.ibm.com,
farman@linux.ibm.com, pmorel@linux.ibm.com,
borntraeger@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com,
gerald.schaefer@linux.ibm.com, agordeev@linux.ibm.com,
frankja@linux.ibm.com, david@redhat.com, imbrenda@linux.ibm.com,
vneethv@linux.ibm.com, oberpar@linux.ibm.com,
freude@linux.ibm.com, thuth@redhat.com, pasic@linux.ibm.com,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 14/30] vfio/pci: re-introduce CONFIG_VFIO_PCI_ZDEV
Date: Mon, 07 Feb 2022 18:59:19 +0100 [thread overview]
Message-ID: <87sfsuv9qg.fsf@redhat.com> (raw)
In-Reply-To: <1ff6e06c-e563-2b9c-3196-542fed7df0f9@linux.ibm.com>
On Mon, Feb 07 2022, Matthew Rosato <mjrosato@linux.ibm.com> wrote:
> On 2/7/22 3:35 AM, Cornelia Huck wrote:
>> On Fri, Feb 04 2022, Matthew Rosato <mjrosato@linux.ibm.com> wrote:
>>
>>> This was previously removed as unnecessary; while that was true, subsequent
>>> changes will make KVM an additional required component for vfio-pci-zdev.
>>> Let's re-introduce CONFIG_VFIO_PCI_ZDEV as now there is actually a reason
>>> to say 'n' for it (when not planning to CONFIG_KVM).
>>
>> Hm... can the file be split into parts that depend on KVM and parts that
>> don't? Does anybody ever use vfio-pci on a non-kvm s390 system?
>>
>
> It is possible to split out most of the prior CLP/ vfio capability work
> (but it would not be a totally clean split, zpci_group_cap for example
> would need to have an inline ifdef since it references a KVM structure)
> -- I suspect we'll see more of that in the future.
> I'm not totally sure if there's value in the information being provided
> today -- this CLP information was all added specifically with
> userspace->guest delivery in mind. And to answer your other question,
> I'm not directly aware of non-kvm vfio-pci usage on s390 today; but that
> doesn't mean there isn't any or won't be in the future of course. With
> this series, you could CONFIG_KVM=n + CONFIG_VFIO_PCI=y|m and you'll get
> the standard vfio-pci support but never any vfio-pci-zdev extension.
Yes. Remind me again: if you do standard vfio-pci without the extensions
grabbing some card-specific information and making them available to the
guest, you get a working setup, it just always looks like a specific
card, right?
>
> If we wanted to provide everything we can where KVM isn't strictly
> required, then let's look at what a split would look like:
>
> With or without KVM:
> zcpi_base_cap
> zpci_group_cap (with an inline ifdef for KVM [1])
> zpci_util_cap
> zpci_pfip_cap
> vfio_pci_info_zdev_add_caps
> vfio_pci_zdev_open (ifdef, just return when !KVM [1])
> vfio_pci_zdev_release (ifdef, just return when !KVM [1])
>
> KVM only:
> vfio_pci_zdev_feat_interp
> vfio_pci_zdev_feat_aif
> vfio_pci_zdev_feat_ioat
> vfio_pci_zdev_group_notifier
>
> I suppose such a split has the benefit of flexibility /
> future-proofing... should a non-kvm use case arrive in the future for
> s390 and we find we need some s390-specific handling, we're still
> building vfio-pci-zdev into vfio-pci by default and can just extend that.
>
> [1] In this case I would propose renaming CONFIG_VFIO_PCI_ZDEV as we
> would once again always be building some part of vfio-pci-zdev with
> vfio-pci on s390 -- maybe something like CONFIG_VFIO_PCI_ZDEV_KVM (wow
> that's a mouthful) and then use this setting to check "KVM" in my above
> split. Since this setting will imply PCI, VFIO_PCI and KVM, we can then
> s/CONFIG_VFIO_PCI_ZDEV/CONFIG_VFIO_PCI_ZDEV_KVM/ for the rest of the
> series (to continue covering cases like we build KVM but not pci, or not
> vfio-pci)
>
> How does that sound?
Complex :)
I'm not really sure whether it's worth the hassle on an odd chance that
we may want it for a !KVM usecase in the future (that goes beyond the
"base" vfio-pci support.) OTOH, it would be cleaner. I'm a bit torn on
this one.
next prev parent reply other threads:[~2022-02-07 18:01 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-04 21:15 [PATCH v3 00/30] KVM: s390: enable zPCI for interpretive execution Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 01/30] s390/sclp: detect the zPCI load/store interpretation facility Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 02/30] s390/sclp: detect the AISII facility Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 03/30] s390/sclp: detect the AENI facility Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 04/30] s390/sclp: detect the AISI facility Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 05/30] s390/airq: pass more TPI info to airq handlers Matthew Rosato
2022-02-07 8:28 ` Cornelia Huck
2022-02-04 21:15 ` [PATCH v3 06/30] s390/airq: allow for airq structure that uses an input vector Matthew Rosato
2022-02-07 8:29 ` Cornelia Huck
2022-02-07 8:42 ` Claudio Imbrenda
2022-02-04 21:15 ` [PATCH v3 07/30] s390/pci: externalize the SIC operation controls and routine Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 08/30] s390/pci: stash associated GISA designation Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 09/30] s390/pci: export some routines related to RPCIT processing Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 10/30] s390/pci: stash dtsm and maxstbl Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 11/30] s390/pci: add helper function to find device by handle Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 12/30] s390/pci: get SHM information from list pci Matthew Rosato
2022-02-07 10:08 ` Pierre Morel
2022-02-04 21:15 ` [PATCH v3 13/30] s390/pci: return status from zpci_refresh_trans Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 14/30] vfio/pci: re-introduce CONFIG_VFIO_PCI_ZDEV Matthew Rosato
2022-02-07 8:35 ` Cornelia Huck
2022-02-07 15:43 ` Matthew Rosato
2022-02-07 17:59 ` Cornelia Huck [this message]
2022-02-07 20:09 ` Matthew Rosato
2022-02-10 10:07 ` Cornelia Huck
2022-02-04 21:15 ` [PATCH v3 15/30] KVM: s390: pci: add basic kvm_zdev structure Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 16/30] KVM: s390: pci: do initial setup for AEN interpretation Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 17/30] KVM: s390: pci: enable host forwarding of Adapter Event Notifications Matthew Rosato
2022-02-14 12:59 ` Pierre Morel
2022-02-14 20:35 ` Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 18/30] KVM: s390: mechanism to enable guest zPCI Interpretation Matthew Rosato
2022-02-14 13:06 ` Pierre Morel
2022-02-04 21:15 ` [PATCH v3 19/30] KVM: s390: pci: provide routines for enabling/disabling interpretation Matthew Rosato
2022-02-14 13:22 ` Pierre Morel
2022-02-04 21:15 ` [PATCH v3 20/30] KVM: s390: pci: provide routines for enabling/disabling interrupt forwarding Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 21/30] KVM: s390: pci: provide routines for enabling/disabling IOAT assist Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 22/30] KVM: s390: pci: handle refresh of PCI translations Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 23/30] KVM: s390: intercept the rpcit instruction Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 24/30] vfio-pci/zdev: wire up group notifier Matthew Rosato
2022-02-08 17:43 ` Alex Williamson
2022-02-08 18:51 ` Jason Gunthorpe
2022-02-08 19:26 ` Alex Williamson
2022-02-08 19:51 ` Jason Gunthorpe
2022-02-08 20:33 ` Matthew Rosato
2022-02-08 20:40 ` Jason Gunthorpe
2022-02-08 21:37 ` Matthew Rosato
2022-02-10 11:15 ` Niklas Schnelle
2022-02-10 13:01 ` Jason Gunthorpe
2022-02-10 14:06 ` Niklas Schnelle
2022-02-10 15:23 ` Jason Gunthorpe
2022-02-10 18:59 ` Matthew Rosato
2022-02-10 23:45 ` Jason Gunthorpe
2022-02-04 21:15 ` [PATCH v3 25/30] vfio-pci/zdev: wire up zPCI interpretive execution support Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 26/30] vfio-pci/zdev: wire up zPCI adapter interrupt forwarding support Matthew Rosato
2022-02-07 16:38 ` Pierre Morel
2022-02-04 21:15 ` [PATCH v3 27/30] vfio-pci/zdev: wire up zPCI IOAT assist support Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 28/30] vfio-pci/zdev: add DTSM to clp group capability Matthew Rosato
2022-02-04 21:15 ` [PATCH v3 29/30] KVM: s390: introduce CPU feature for zPCI Interpretation Matthew Rosato
2022-02-07 16:36 ` Pierre Morel
2022-02-04 21:15 ` [PATCH v3 30/30] MAINTAINERS: additional files related kvm s390 pci passthrough Matthew Rosato
2022-02-07 13:04 ` Christian Borntraeger
2022-02-07 15:44 ` Matthew Rosato
2022-02-04 21:33 ` [PATCH v3 00/30] KVM: s390: enable zPCI for interpretive execution Matthew Rosato
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