netdev - Re: [PATCH net-next 16/19] net/mlx5: Implement dma ops and params for mediated device

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Date:   Thu, 7 Nov 2019 20:16:53 -0500
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Parav Pandit <parav@...lanox.com>
Cc:     "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "leon@...nel.org" <leon@...nel.org>,
        "cohuck@...hat.com" <cohuck@...hat.com>,
        Jiri Pirko <jiri@...lanox.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
Subject: Re: [PATCH net-next 16/19] net/mlx5: Implement dma ops and params
 for mediated device

On Thu, 7 Nov 2019 21:30:41 +0000, Parav Pandit wrote:
> > -----Original Message-----
> > From: kvm-owner@...r.kernel.org <kvm-owner@...r.kernel.org> On Behalf
> > Of Jakub Kicinski
> > Sent: Thursday, November 7, 2019 2:43 PM
> > To: Parav Pandit <parav@...lanox.com>
> > Cc: alex.williamson@...hat.com; davem@...emloft.net;
> > kvm@...r.kernel.org; netdev@...r.kernel.org; Saeed Mahameed
> > <saeedm@...lanox.com>; kwankhede@...dia.com; leon@...nel.org;
> > cohuck@...hat.com; Jiri Pirko <jiri@...lanox.com>; linux-
> > rdma@...r.kernel.org
> > Subject: Re: [PATCH net-next 16/19] net/mlx5: Implement dma ops and params
> > for mediated device

Please try to avoid generating those headers, you're not an occasional
contributor. They're annoying and a waste of space :(

> > On Thu,  7 Nov 2019 10:08:31 -0600, Parav Pandit wrote:  
> > > Implement dma ops wrapper to divert dma ops to its parent PCI device
> > > because Intel IOMMU (and may be other IOMMU) is limited to PCI devices.
> > >
> > > Reviewed-by: Saeed Mahameed <saeedm@...lanox.com>
> > > Signed-off-by: Parav Pandit <parav@...lanox.com>  
> > 
> > Isn't this supposed to use PASSID or whatnot? Could you explain a little? This
> > mdev stuff is pretty new to networking folks..  
> 
> Currently series doesn't support PCI PASID.
> While doing dma mapping, Intel IOMMU expects dma device to be PCI device in few function traces like, find_or_alloc_domain(), 
> Since mdev bus is not a PCI bus, DMA mapping needs to go through its parent PCI device.
> Otherwise dma ops on mdev devices fails, as I think it fails to identify how to perform the translations.
> (It doesn't seem to consult its parent device).

What's missing for PASSID to work? HW support? FW support? IOMMU
plumbing? mdev plumbing? mlx5 plumbing?