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Date:   Wed, 8 May 2019 08:02:55 -0400
From:   Yan Zhao <yan.y.zhao@intel.com>
To:     Cornelia Huck <cohuck@redhat.com>
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        "Tian, Kevin" <kevin.tian@intel.com>,
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        "Wang, Zhi A" <zhi.a.wang@intel.com>,
        "cjia@nvidia.com" <cjia@nvidia.com>,
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Subject: Re: [PATCH v2 2/2] drm/i915/gvt: export mdev device version to sysfs
 for Intel vGPU
Message-ID: <20190508120255.GC24397@joy-OptiPlex-7040>
Reply-To: Yan Zhao <yan.y.zhao@intel.com>
References: <20190506014514.3555-1-yan.y.zhao@intel.com>
 <20190506015102.3691-1-yan.y.zhao@intel.com>
 <20190507112753.2699d0b5.cohuck@redhat.com>
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On Tue, May 07, 2019 at 05:27:53PM +0800, Cornelia Huck wrote:
> On Sun,  5 May 2019 21:51:02 -0400
> Yan Zhao <yan.y.zhao@intel.com> wrote:
> 
> > This feature implements the version attribute for Intel's vGPU mdev
> > devices.
> > 
> > version attribute is rw.
> > It's used to check device compatibility for two mdev devices.
> > version string format and length are private for vendor driver. vendor
> > driver is able to define them freely.
> > 
> > For Intel vGPU of gen8 and gen9, the mdev device version
> > consists of 3 fields: "vendor id" + "device id" + "mdev type".
> > 
> > Reading from a vGPU's version attribute, a string is returned in below
> > format: <vendor id>-<device id>-<mdev type>. e.g.
> > 8086-193b-i915-GVTg_V5_2.
> > 
> > Writing a string to a vGPU's version attribute will trigger GVT to check
> > whether a vGPU identified by the written string is compatible with
> > current vGPU owning this version attribute. errno is returned if the two
> > vGPUs are incompatible. The length of written string is returned in
> > compatible case.
> > 
> > For other platforms, and for GVT not supporting vGPU live migration
> > feature, errnos are returned when read/write of mdev devices' version
> > attributes.
> > 
> > For old GVT versions where no version attributes exposed in sysfs, it is
> > regarded as not supporting vGPU live migration.
> > 
> > For future platforms, besides the current 2 fields in vendor proprietary
> > part, more fields may be added to identify Intel vGPU well for live
> > migration purpose.
> > 
> > v2:
> > 1. removed 32 common part of version string
> > (Alex Williamson)
> > 2. do not register version attribute for GVT not supporting live
> > migration.(Cornelia Huck)
> > 3. for platforms out of gen8, gen9, return -EINVAL --> -ENODEV for
> > incompatible. (Cornelia Huck)
> 
> Should go below '---'.
>
got it. will change it in next revision.

> > 
> > Cc: Alex Williamson <alex.williamson@redhat.com>
> > Cc: Erik Skultety <eskultet@redhat.com>
> > Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > Cc: Cornelia Huck <cohuck@redhat.com>
> > Cc: "Tian, Kevin" <kevin.tian@intel.com>
> > Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
> > Cc: "Wang, Zhi A" <zhi.a.wang@intel.com>
> > c: Neo Jia <cjia@nvidia.com>
> > Cc: Kirti Wankhede <kwankhede@nvidia.com>
> > 
> > Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
> > ---
> >  drivers/gpu/drm/i915/gvt/Makefile         |  2 +-
> >  drivers/gpu/drm/i915/gvt/device_version.c | 87 +++++++++++++++++++++++
> >  drivers/gpu/drm/i915/gvt/gvt.c            | 51 +++++++++++++
> >  drivers/gpu/drm/i915/gvt/gvt.h            |  6 ++
> >  4 files changed, 145 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/gpu/drm/i915/gvt/device_version.c
> > 
> 
> (...)
> 
> > diff --git a/drivers/gpu/drm/i915/gvt/device_version.c b/drivers/gpu/drm/i915/gvt/device_version.c
> > new file mode 100644
> > index 000000000000..bd4cdcbdba95
> > --- /dev/null
> > +++ b/drivers/gpu/drm/i915/gvt/device_version.c
> > @@ -0,0 +1,87 @@
> > +/*
> > + * Copyright(c) 2011-2017 Intel Corporation. All rights reserved.
> > + *
> > + * Permission is hereby granted, free of charge, to any person obtaining a
> > + * copy of this software and associated documentation files (the "Software"),
> > + * to deal in the Software without restriction, including without limitation
> > + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> > + * and/or sell copies of the Software, and to permit persons to whom the
> > + * Software is furnished to do so, subject to the following conditions:
> > + *
> > + * The above copyright notice and this permission notice (including the next
> > + * paragraph) shall be included in all copies or substantial portions of the
> > + * Software.
> > + *
> > + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> > + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> > + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> > + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> > + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
> > + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
> > + * SOFTWARE.
> > + *
> > + * Authors:
> > + *    Yan Zhao <yan.y.zhao@intel.com>
> > + */
> > +#include <linux/vfio.h>
> > +#include "i915_drv.h"
> > +
> > +static bool is_compatible(const char *self, const char *remote)
> > +{
> > +	if (strlen(remote) != strlen(self))
> > +		return false;
> > +
> > +	return (strncmp(self, remote, strlen(self))) ? false : true;
> > +}
> > +
> > +ssize_t intel_gvt_get_vfio_device_version_len(struct drm_i915_private *dev_priv)
> > +{
> > +	if (!IS_GEN(dev_priv, 8) && !IS_GEN(dev_priv, 9))
> > +		return -ENODEV;
> > +
> > +	return PAGE_SIZE;
> > +}
> > +
> > +ssize_t intel_gvt_get_vfio_device_version(struct drm_i915_private *dev_priv,
> > +		char *buf, const char *mdev_type)
> > +{
> > +	int cnt = 0, ret = 0;
> > +	const char *str = NULL;
> > +
> > +	/* currently only gen8 & gen9 are supported */
> > +	if (!IS_GEN(dev_priv, 8) && !IS_GEN(dev_priv, 9))
> > +		return -ENODEV;
> > +
> > +	/* vendor id + device id + mdev type */
> > +	/* vendor id */
> > +	cnt = snprintf(buf, 5, "%04x", PCI_VENDOR_ID_INTEL);
> > +	buf += cnt;
> > +	ret += cnt;
> > +
> > +	/* device id */
> > +	cnt = snprintf(buf, 6, "-%04x", INTEL_DEVID(dev_priv));
> > +	buf += cnt;
> > +	ret += cnt;
> > +
> > +	/* mdev type */
> > +	str = mdev_type;
> > +	cnt = snprintf(buf, strlen(str) + 3, "-%s\n", mdev_type);
> > +	buf += cnt;
> > +	ret += cnt;
> > +
> > +	return ret;
> 
> I'm not familiar with this driver; but would it make sense to pre-build
> the version on init? It does not look to me like the values could
> change dynamically.
>
yes. I intended to save some memory by not pre-building the version on init, as
migration is a rare event. but as these version strings are not big, moving them
to init is also good. I'll do it in next revision.
thanks:)


> > +}
> > +
> > +ssize_t intel_gvt_check_vfio_device_version(struct drm_i915_private *dev_priv,
> > +		const char *self, const char *remote)
> > +{
> > +
> > +	/* currently only gen8 & gen9 are supported */
> > +	if (!IS_GEN(dev_priv, 8) && !IS_GEN(dev_priv, 9))
> > +		return -ENODEV;
> > +
> > +	if (!is_compatible(self, remote))
> > +		return -EINVAL;
> > +
> > +	return 0;
> > +}
> 
> Return values look reasonable to me. I'll leave discussions regarding
> where the attribute should go to folks familiar with this driver.
ok. thanks :)