From: Thomas Gleixner <tglx@linutronix.de>
To: Dave Jiang <dave.jiang@intel.com>, Jason Gunthorpe <jgg@nvidia.com>
Cc: Allen Hubbe <allenbh@gmail.com>,
linux-s390@vger.kernel.org, Kevin Tian <kevin.tian@intel.com>,
x86@kernel.org, Ashok Raj <ashok.raj@intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Marc Zygnier <maz@kernel.org>, Heiko Carstens <hca@linux.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
iommu@lists.linux-foundation.org,
Christian Borntraeger <borntraeger@de.ibm.com>,
Alex Williamson <alex.williamson@redhat.com>,
Joerg Roedel <jroedel@suse.de>,
Bjorn Helgaas <helgaas@kernel.org>,
linux-pci@vger.kernel.org, linux-ntb@googlegroups.com,
Logan Gunthorpe <logang@deltatee.com>,
Megha Dey <megha.dey@intel.com>
Subject: Re: [patch 21/32] NTB/msi: Convert to msi_on_each_desc()
Date: Wed, 01 Dec 2021 21:25:53 +0100 [thread overview]
Message-ID: <87k0go8432.ffs@tglx> (raw)
In-Reply-To: <df00b87e-00dc-d998-8b64-46b16dba46eb@intel.com>
On Wed, Dec 01 2021 at 11:47, Dave Jiang wrote:
> On 12/1/2021 11:41 AM, Thomas Gleixner wrote:
>>> Hi Thomas. This is actually the IDXD usage for a mediated device passed
>>> to a guest kernel when we plumb the pass through of IMS to the guest
>>> rather than doing previous implementation of having a MSIX vector on
>>> guest backed by IMS.
>> Which makes a lot of sense.
>>
>>> The control block for the mediated device is emulated and therefore an
>>> emulated MSIX vector will be surfaced as vector 0. However the queues
>>> will backed by IMS vectors. So we end up needing MSIX and IMS coexist
>>> running on the guest kernel for the same device.
>> Why? What's wrong with using straight MSI-X for all of them?
>
> The hardware implementation does not have enough MSIX vectors for
> guests. There are only 9 MSIX vectors total (8 for queues) and 2048 IMS
> vectors. So if we are to do MSI-X for all of them, then we need to do
> the IMS backed MSIX scheme rather than passthrough IMS to guests.
Confused. Are you talking about passing a full IDXD device to the guest
or about passing a carved out subdevice, aka. queue?
Thanks,
tglx
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next prev parent reply other threads:[~2021-12-01 20:26 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20211126230957.239391799@linutronix.de>
[not found] ` <20211126232735.547996838@linutronix.de>
[not found] ` <7daba0e2-73a3-4980-c3a5-a71f6b597b22@deltatee.com>
[not found] ` <874k7ueldt.ffs@tglx>
[not found] ` <6ba084d6-2b26-7c86-4526-8fcd3d921dfd@deltatee.com>
[not found] ` <87ilwacwp8.ffs@tglx>
[not found] ` <d6f13729-1b83-fa7d-3f0d-98d4e3f7a2aa@deltatee.com>
[not found] ` <87v909bf2k.ffs@tglx>
[not found] ` <20211130202800.GE4670@nvidia.com>
[not found] ` <87o861banv.ffs@tglx>
[not found] ` <20211201001748.GF4670@nvidia.com>
2021-12-01 10:16 ` [patch 21/32] NTB/msi: Convert to msi_on_each_desc() Thomas Gleixner
2021-12-01 13:00 ` Jason Gunthorpe via iommu
2021-12-01 17:35 ` Thomas Gleixner
2021-12-01 18:14 ` Jason Gunthorpe via iommu
2021-12-01 18:46 ` Logan Gunthorpe
2021-12-01 20:21 ` Thomas Gleixner
2021-12-02 0:01 ` Thomas Gleixner
2021-12-02 13:55 ` Jason Gunthorpe via iommu
2021-12-02 14:23 ` Greg Kroah-Hartman
2021-12-02 14:45 ` Jason Gunthorpe via iommu
2021-12-02 19:25 ` Thomas Gleixner
2021-12-02 20:00 ` Jason Gunthorpe via iommu
2021-12-02 22:31 ` Thomas Gleixner
2021-12-03 0:37 ` Jason Gunthorpe via iommu
2021-12-03 15:07 ` Thomas Gleixner
2021-12-03 16:41 ` Jason Gunthorpe via iommu
2021-12-04 14:20 ` Thomas Gleixner
2021-12-05 14:16 ` Thomas Gleixner
2021-12-06 14:43 ` Jason Gunthorpe via iommu
2021-12-06 15:47 ` Thomas Gleixner
2021-12-06 17:00 ` Jason Gunthorpe via iommu
2021-12-06 20:28 ` Thomas Gleixner
2021-12-06 21:06 ` Jason Gunthorpe via iommu
2021-12-06 22:21 ` Thomas Gleixner
2021-12-06 14:19 ` Jason Gunthorpe via iommu
2021-12-06 15:06 ` Thomas Gleixner
2021-12-09 6:26 ` Tian, Kevin
2021-12-09 9:03 ` Thomas Gleixner
2021-12-09 12:17 ` Tian, Kevin
2021-12-09 15:57 ` Thomas Gleixner
2021-12-10 7:37 ` Tian, Kevin
2021-12-09 5:41 ` Tian, Kevin
2021-12-09 5:47 ` Jason Wang
2021-12-01 16:28 ` Dave Jiang
2021-12-01 18:41 ` Thomas Gleixner
2021-12-01 18:47 ` Dave Jiang
2021-12-01 20:25 ` Thomas Gleixner [this message]
2021-12-01 21:21 ` Dave Jiang
2021-12-01 21:44 ` Thomas Gleixner
2021-12-01 21:49 ` Dave Jiang
2021-12-01 22:03 ` Thomas Gleixner
2021-12-01 22:53 ` Dave Jiang
2021-12-01 23:57 ` Thomas Gleixner
2021-12-09 5:23 ` Tian, Kevin
2021-12-09 8:37 ` Thomas Gleixner
2021-12-09 12:31 ` Tian, Kevin
2021-12-09 16:21 ` Jason Gunthorpe via iommu
2021-12-09 20:32 ` Thomas Gleixner
2021-12-09 20:58 ` Jason Gunthorpe via iommu
2021-12-09 22:09 ` Thomas Gleixner
2021-12-10 0:26 ` Thomas Gleixner
2021-12-10 7:29 ` Tian, Kevin
2021-12-10 12:13 ` Thomas Gleixner
2021-12-11 8:06 ` Tian, Kevin
2021-12-10 12:39 ` Jason Gunthorpe via iommu
2021-12-10 19:00 ` Thomas Gleixner
2021-12-11 7:44 ` Tian, Kevin
2021-12-11 13:04 ` Thomas Gleixner
2021-12-12 1:56 ` Tian, Kevin
2021-12-12 20:55 ` Thomas Gleixner
2021-12-12 23:37 ` Jason Gunthorpe via iommu
2021-12-13 7:50 ` Tian, Kevin
2021-12-11 7:52 ` Tian, Kevin
2021-12-12 0:12 ` Thomas Gleixner
2021-12-12 2:14 ` Tian, Kevin
2021-12-12 20:50 ` Thomas Gleixner
2021-12-12 23:42 ` Jason Gunthorpe via iommu
2021-12-10 7:36 ` Tian, Kevin
2021-12-10 12:30 ` Jason Gunthorpe via iommu
2021-12-12 6:44 ` Mika Penttilä
2021-12-12 23:27 ` Jason Gunthorpe via iommu
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