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Date: Wed, 1 Dec 2021 15:53:46 -0700
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Subject: Re: [patch 21/32] NTB/msi: Convert to msi_on_each_desc()
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From: Dave Jiang <dave.jiang@intel.com>
In-Reply-To: <875ys87zl5.ffs@tglx>
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To: Thomas Gleixner <tglx@linutronix.de>, Jason Gunthorpe <jgg@nvidia.com>
Cc: Logan Gunthorpe <logang@deltatee.com>, LKML <linux-kernel@vger.kernel.org>, Bjorn Helgaas <helgaas@kernel.org>, Marc Zygnier <maz@kernel.org>, Alex Williamson <alex.williamson@redhat.com>, Kevin Tian <kevin.tian@intel.com>, Megha Dey <megha.dey@intel.com>, Ashok Raj <ashok.raj@intel.com>, linux-pci@vger.kernel.org, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Jon Mason <jdmason@kudzu.us>, Allen Hubbe <allenbh@gmail.com>, linux-ntb@googlegroups.com, linux-s390@vger.kernel.org, Heiko Carstens <hca@linux.ibm.com>, Christian Borntraeger <borntraeger@de.ibm.com>, x86@kernel.org, Joerg Roedel <jroedel@suse.de>, iommu@lists.linux-foundation.org
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On 12/1/2021 3:03 PM, Thomas Gleixner wrote:
> On Wed, Dec 01 2021 at 14:49, Dave Jiang wrote:
>> On 12/1/2021 2:44 PM, Thomas Gleixner wrote:
>>> How that is backed on the host does not really matter. You can expose
>>> MSI-X to the guest with a INTx backing as well.
>>>
>>> I'm still failing to see the connection between the 9 MSIX vectors and
>>> the 2048 IMS vectors which I assume that this is the limitation of the
>>> physical device, right?
>> I think I was confused with what you were asking and was thinking you
>> are saying why can't we just have MSIX on guest backed by the MSIX on
>> the physical device and thought there would not be enough vectors to
>> service the many guests. I think I understand what your position is now
>> with the clarification above.
> This still depends on how this overall discussion about representation
> of all of this stuff is resolved.
>
>>> What needs a subdevice to expose?
> Can you answer that too please?

Sorry. So initial version of the IDXD sub-device is represented with a 
single queue. It needs a command irq (emulated) and a completion irq 
that is backed by a device vector (currently IMS).


>
> Thanks,
>
>          tglx