linux-kernel - Re: [PATCH v6 00/20] Add VFIO mediated device support and DEV-MSI support for the idxd driver

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Message-ID: <20210523232219.GG1002214@nvidia.com>
Date:   Sun, 23 May 2021 20:22:19 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Dave Jiang <dave.jiang@...el.com>
Cc:     alex.williamson@...hat.com, kwankhede@...dia.com,
        tglx@...utronix.de, vkoul@...nel.org,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, megha.dey@...el.com,
        jacob.jun.pan@...el.com, yi.l.liu@...el.com, baolu.lu@...el.com,
        sanjay.k.kumar@...el.com, tony.luck@...el.com,
        dan.j.williams@...el.com, eric.auger@...hat.com,
        pbonzini@...hat.com, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v6 00/20] Add VFIO mediated device support and DEV-MSI
 support for the idxd driver

On Fri, May 21, 2021 at 05:19:05PM -0700, Dave Jiang wrote:

> The code has dependency on DEV_MSI/IMS enabling code:
> https://lore.kernel.org/lkml/1614370277-23235-1-git-send-email-megha.dey@intel.com/
> 
> The code has dependency on idxd driver sub-driver cleanup series:
> https://lore.kernel.org/dmaengine/162163546245.260470.18336189072934823712.stgit@djiang5-desk3.ch.intel.com/T/#t
> 
> The code has dependency on Jason's VFIO refactoring:
> https://lore.kernel.org/kvm/0-v2-7667f42c9bad+935-vfio3_jgg@nvidia.com/

That is quite an inter-tangled list, do you have a submission plan??

> Introducing mdev types “1dwq-v1” type. This mdev type allows
> allocation of a single dedicated wq from available dedicated wqs. After
> a workqueue (wq) is enabled, the user will generate an uuid. On mdev
> creation, the mdev driver code will find a dwq depending on the mdev
> type. When the create operation is successful, the user generated uuid
> can be passed to qemu. When the guest boots up, it should discover a
> DSA device when doing PCI discovery.
> 
> For example of “1dwq-v1” type:
> 1. Enable wq with “mdev” wq type
> 2. A user generated uuid.
> 3. The uuid is written to the mdev class sysfs path:
> echo $UUID > /sys/class/mdev_bus/0000\:00\:0a.0/mdev_supported_types/idxd-1dwq-v1/create
> 4. Pass the following parameter to qemu:
> "-device vfio-pci,sysfsdev=/sys/bus/pci/devices/0000:00:0a.0/$UUID"

So the idxd core driver knows to create a "vfio" wq with its own much
machinery but you still want to involve the horrible mdev guid stuff?

Why??

Jason