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From: Matthew Rosato <mjrosato@linux.ibm.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
	linux-s390@vger.kernel.org, cohuck@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 24/30] vfio-pci/zdev: wire up group notifier
Date: Tue, 8 Feb 2022 16:37:55 -0500	[thread overview]
Message-ID: <920cf807-efcd-319b-560a-ed3a1c6fdc85@linux.ibm.com> (raw)
In-Reply-To: <20220208204041.GK4160@nvidia.com>

On 2/8/22 3:40 PM, Jason Gunthorpe wrote:
> On Tue, Feb 08, 2022 at 03:33:58PM -0500, Matthew Rosato wrote:
> 
>>> Is the purpose of IOAT to associate the device to a set of KVM page
>>> tables?  That seems like a container or future iommufd operation.  I
>>
>> Yes, here we are establishing a relationship with the DMA table in the guest
>> so that once mappings are established guest PCI operations (handled via
>> special instructions in s390) don't need to go through the host but can be
>> directly handled by firmware (so, effectively guest can keep running on its
>> vcpu vs breaking out).
> 
> Oh, well, certainly sounds like a NAK on that - anything to do with
> the DMA translation of a PCI device must go through the iommu layer,
> not here.
> 
> Lets not repeat the iommu subsytem bypass mess power made please.
> 
>> It's more that non-KVM userspace doesn't care about what these ioctls are
>> doing...  The enabling of 'interp, aif, ioat' is only pertinent when there
>> is a KVM userspace, specifically because the information being shared /
>> actions being performed as a result are only relevant to properly enabling
>> zPCI features when the zPCI device is being passed through to a VM
>> guest.
> 
> Then why are they KVM ioctls?

Well, the primary reason I ended up here was that I need to ensure the 
the operation is only performed when guest X owns host zPCI device Y. 
The vfio-pci device ioctl had the benefit of acting on device 
granularity + also already being aware of the host PCI (and thus zPCI) 
device association -- so I already know exactly what hostdev is being 
referenced for the operation.  All that was needed was the KVM notifier 
to ensure the vfio device was associated to a KVM guest.

I think moving over to a KVM ioctl is doable; I might still need to rely 
on VFIO_GROUP_NOTIFY_SET_KVM though, not sure yet.

Based on prior comments in this thread I'm assuming Alex shares that 
view too (don't use vfio device ioctl for something only being used for 
VM passthrough) so I'll start looking at using KVM ioctls instead.


  reply	other threads:[~2022-02-08 22:23 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
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 [this message]
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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