linux-kernel - Re: [PATCH v3 2/3] vfio: zpci: defining the VFIO headers

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Message-ID: <20190528155428.0f149994@x1.home>
Date:   Tue, 28 May 2019 15:54:28 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Cornelia Huck <cohuck@...hat.com>
Cc:     Pierre Morel <pmorel@...ux.ibm.com>, sebott@...ux.vnet.ibm.com,
        gerald.schaefer@...ibm.com, pasic@...ux.vnet.ibm.com,
        borntraeger@...ibm.com, walling@...ux.ibm.com,
        linux-s390@...r.kernel.org, iommu@...ts.linux-foundation.org,
        joro@...tes.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        robin.murphy@....com
Subject: Re: [PATCH v3 2/3] vfio: zpci: defining the VFIO headers

On Thu, 23 May 2019 18:24:33 +0200
Cornelia Huck <cohuck@...hat.com> wrote:

> On Thu, 23 May 2019 14:25:25 +0200
> Pierre Morel <pmorel@...ux.ibm.com> wrote:
> 
> > We define a new device region in vfio.h to be able to
> > get the ZPCI CLP information by reading this region from
> > userland.
> > 
> > We create a new file, vfio_zdev.h to define the structure
> > of the new region we defined in vfio.h
> > 
> > Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
> > ---
> >  include/uapi/linux/vfio.h      |  4 ++++
> >  include/uapi/linux/vfio_zdev.h | 34 ++++++++++++++++++++++++++++++++++
> >  2 files changed, 38 insertions(+)
> >  create mode 100644 include/uapi/linux/vfio_zdev.h
> > 
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index 8f10748..56595b8 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -306,6 +306,10 @@ struct vfio_region_info_cap_type {
> >  #define VFIO_REGION_TYPE_GFX                    (1)
> >  #define VFIO_REGION_SUBTYPE_GFX_EDID            (1)
> >  
> > +/* IBM Subtypes */
> > +#define VFIO_REGION_TYPE_IBM_ZDEV		(1)
> > +#define VFIO_REGION_SUBTYPE_ZDEV_CLP		(1)  
> 
> I'm afraid that confuses me a bit. You want to add the region to every
> vfio-pci device when we're running under s390, right? So this does not
> depend on the device type of the actual device (which may or may not be
> from IBM), but only on the architecture?

FWIW, I don't really have a strong opinion here but I welcome the
discussion.  It seems fair to me that a PCI vendor type could be used
for either a device with that vendor ID or by the vendor of the
platform.  We've got a lot of address space if want to use
VFIO_REGION_TYPE_IBM_ZDEV rather than a PCI vendor type (so long as
it's updated not to conflict with the GFX type).  Thanks,

Alex
 
> (Generally speaking, I think using regions for this makes sense,
> though.)
> 
> > +
> >  /**
> >   * struct vfio_region_gfx_edid - EDID region layout.
> >   *
> > diff --git a/include/uapi/linux/vfio_zdev.h
> > b/include/uapi/linux/vfio_zdev.h new file mode 100644
> > index 0000000..84b1a82
> > --- /dev/null
> > +++ b/include/uapi/linux/vfio_zdev.h
> > @@ -0,0 +1,34 @@
> > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> > +/*
> > + * Region definition for ZPCI devices
> > + *
> > + * Copyright IBM Corp. 2019
> > + *
> > + * Author(s): Pierre Morel <pmorel@...ux.ibm.com>
> > + */
> > +
> > +#ifndef _VFIO_ZDEV_H_
> > +#define _VFIO_ZDEV_H_
> > +
> > +#include <linux/types.h>
> > +
> > +/**
> > + * struct vfio_region_zpci_info - ZPCI information.
> > + *
> > + */
> > +struct vfio_region_zpci_info {
> > +	__u64 dasm;
> > +	__u64 start_dma;
> > +	__u64 end_dma;
> > +	__u64 msi_addr;
> > +	__u64 flags;
> > +	__u16 pchid;
> > +	__u16 mui;
> > +	__u16 noi;
> > +	__u8 gid;
> > +	__u8 version;
> > +#define VFIO_PCI_ZDEV_FLAGS_REFRESH 1
> > +	__u8 util_str[CLP_UTIL_STR_LEN];
> > +} __packed;
> > +
> > +#endif  
>