[dpdk-dev] [RFC PATCH] bus/pci: avoid depending on private value in kernel source

David Marchand david.marchand at redhat.com
Wed Jul 3 10:01:44 CEST 2019


On Wed, Jul 3, 2019 at 9:58 AM Tiwei Bie <tiwei.bie at intel.com> wrote:

> On Wed, Jul 03, 2019 at 09:36:26AM +0200, David Marchand wrote:
> > On Wed, Jul 3, 2019 at 9:35 AM Tiwei Bie <tiwei.bie at intel.com> wrote:
> >
> >     Hi David,
> >
> >     On Wed, Jul 03, 2019 at 09:02:59AM +0200, David Marchand wrote:
> >     > Hello,
> >     >
> >     > On Wed, Jul 3, 2019 at 7:47 AM Tiwei Bie <tiwei.bie at intel.com>
> wrote:
> >     >
> >     >     The value 40 used in VFIO_GET_REGION_ADDR() is a private value
> >     >     (VFIO_PCI_OFFSET_SHIFT) defined in Linux kernel source [1]. It
> >     >     is not part of VFIO API, and we should not depend on it.
> >     >
> >     >     [1]
> https://github.com/torvalds/linux/blob/6fbc7275c7a9/drivers/vfio/
> >     pci/
> >     >     vfio_pci_private.h#L19
> >     >
> >     >
> >     >
> >     > I did not follow linux kernel changes, is there something that
> would
> >     change
> >     > this offset?
> >     > It looks like a cleanup (did not look into the details yet), do we
> need
> >     this
> >     > now?
> >
> >     In VFIO/mdev [1], the offset can be something different. It depends
> >     on the parent device. It's not just a cleanup. It's a preparation
> >     for the mdev support in DPDK.
> >
> >     [1] https://github.com/torvalds/linux/blob/master/Documentation/
> >     vfio-mediated-device.txt
> >
> >
> >
> > Ok, thanks.
> > So we can wait for mdev to be ready before working on this.
>
> What do you mean by "mdev to be ready"? RFC ready? I don't see
> anything blocking the discussion on this now.
>
> PS. I already sent a RFC series of the mdev support in DPDK
>     to the mailing list 3 month ago.
>

If you need it and the mdev support has been posted already, why not send a
n+1 patchset with this patch in it?

This patch alone looked odd to me.
I want to understand if this is a fix we need now or something that can
wait.
We have a really large backlog.


-- 
David Marchand


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