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From: Thomas Gleixner <tglx@linutronix.de>
Subject: RE: [patch 21/32] NTB/msi: Convert to msi_on_each_desc()
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Date: Sun, 12 Dec 2021 21:55:32 +0100
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To: "Tian, Kevin" <kevin.tian@intel.com>, Jason Gunthorpe <jgg@nvidia.com>
Cc: "Jiang, Dave" <dave.jiang@intel.com>, 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>, "Dey, Megha" <megha.dey@intel.com>, "Raj,
 Ashok" <ashok.raj@intel.com>, "linux-pci@vger.kernel.org" <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-ntb@googlegroups.com>, "linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>, Heiko Carstens <hca@linux.ibm.com>, Christian Borntraeger <borntraeger@de.ibm.com>, "x86@kernel.org" <x86@kernel.org>, "Rodel, Jorg" <jroedel@suse.de>, "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>
List-ID: <linux-ntb.googlegroups.com>

Kevin,

On Sun, Dec 12 2021 at 01:56, Kevin Tian wrote:
>> From: Thomas Gleixner <tglx@linutronix.de>
>> All I can find is drivers/iommu/virtio-iommu.c but I can't find anything
>> vIR related there.
>
> Well, virtio-iommu is a para-virtualized vIOMMU implementations.
>
> In reality there are also fully emulated vIOMMU implementations (e.g.
> Qemu fully emulates Intel/AMD/ARM IOMMUs). In those configurations
> the IR logic in existing iommu drivers just apply:
>
> 	drivers/iommu/intel/irq_remapping.c
> 	drivers/iommu/amd/iommu.c

thanks for the explanation. So that's a full IOMMU emulation. I was more
expecting a paravirtualized lightweight one.

Thanks,

        tglx