Re: [dpdk-dev] [EXT] Re: [PATCH] bus/pci: fix IOVA as VA mode selection

From: Jerin Jacob Kollanukkaran <jerinj@marvell.com>
To: "Burakov, Anatoly" <anatoly.burakov@intel.com>,
	David Marchand <david.marchand@redhat.com>
Cc: dev <dev@dpdk.org>, Thomas Monjalon <thomas@monjalon.net>,
	Ben Walker <benjamin.walker@intel.com>
Subject: Re: [dpdk-dev] [EXT] Re: [PATCH] bus/pci: fix IOVA as VA mode selection
Date: Tue, 9 Jul 2019 11:13:58 +0000	[thread overview]
Message-ID: <BYAPR18MB2424F6ECEC20B0114BB031CEC8F10@BYAPR18MB2424.namprd18.prod.outlook.com> (raw)
In-Reply-To: <ef1779e4-f553-153c-062e-ce47f0293a2d@intel.com>

> -----Original Message-----
> From: Burakov, Anatoly <anatoly.burakov@intel.com>
> Sent: Tuesday, July 9, 2019 3:15 PM
> To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>; David Marchand
> <david.marchand@redhat.com>
> Cc: dev <dev@dpdk.org>; Thomas Monjalon <thomas@monjalon.net>; Ben
> Walker <benjamin.walker@intel.com>
> Subject: Re: [EXT] Re: [dpdk-dev] [PATCH] bus/pci: fix IOVA as VA mode
> selection
> 
> On 08-Jul-19 8:13 PM, Jerin Jacob Kollanukkaran wrote:
> > See below,
> >
> > Please send the email as text to avoid formatting issue.(No HTML)
> >
> > From: David Marchand <david.marchand@redhat.com>
> > Sent: Tuesday, July 9, 2019 12:09 AM
> > To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>
> > Cc: dev <dev@dpdk.org>; Thomas Monjalon <thomas@monjalon.net>;
> Ben
> > Walker <benjamin.walker@intel.com>; Burakov, Anatoly
> > <anatoly.burakov@intel.com>
> > Subject: [EXT] Re: [dpdk-dev] [PATCH] bus/pci: fix IOVA as VA mode
> > selection
> >
> > ________________________________________
> >
> > On Mon, Jul 8, 2019 at 4:25 PM <mailto:jerinj@marvell.com> wrote:
> > From: Jerin Jacob <mailto:jerinj@marvell.com>
> >
> > Existing logic fails to select IOVA mode as VA if driver request to
> > enable IOVA as VA.
> >
> > IOVA as VA has more strict requirement than other modes, so enabling
> > positive logic for IOVA as VA selection.
> >
> > This patch also updates the default IOVA mode as PA for PCI devices as
> > it has to deal with DMA engines unlike the virtual devices that may
> > need only IOVA as DC.
> >
> > We have three cases:
> > - driver/hw supports IOVA as PA only
> >
> > [Jerin] It is not driver cap, it is more of system cap(IOMMU vs non
> > IOMMU). We are already addressing that case
> 
> I don't get how this works. How does "system capability" affect what the
> device itself supports? Are we to assume that *all* hardware support IOVA
> as VA by default? "System capability" is more of a bus issue than an individual
> device issue, is it not?

What I meant is, supporting VA vs PA is function of IOMMU(not the device attribute).
Ie. Device makes the  bus master request, if IOMMU available and enabled in the SYSTEM ,
It goes over IOMMU  and translate the IOVA to physical address.

Another way to put is, Is there any _PCIe_ device which need/requires
RTE_PCI_DRV_NEED_IOVA_AS_PA in rte_pci_driver.drv_flags

> 
> --
> Thanks,
> Anatoly