Re: [libvirt] [PATCH 2/2] drm/i915/gvt: export mdev device version to sysfs for Intel vGPU

On Fri, 19 Apr 2019 04:35:59 -0400 Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > This feature implements the version attribute for Intel's vGPU mdev > devices. > > version attribute is rw. It is queried by userspace software like libvirt > to check whether two vGPUs are compatible for live migration. > > It consists of two parts: common part and vendor proprietary part. > common part: 32 bit. lower 16 bits is vendor id and higher 16 bits > identifies device type. e.g., for pci device, it is > "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). > vendor proprietary part: this part is varied in length. vendor driver can > specify any string to identify a device. > > For Intel vGPU of gen8 and gen9, the vendor proprietary part currently > consists of 2 fields: "device id" + "mdev type". > > Reading from a vGPU's version attribute, a string is returned in below > format: 00028086-<device id>-<mdev type>. e.g. > 00028086-193b-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. > > Cc: Alex Williamson <alex.williamson(a)redhat.com&gt; > Cc: Erik Skultety <eskultet(a)redhat.com&gt; > Cc: "Dr. David Alan Gilbert" <dgilbert(a)redhat.com&gt; > Cc: Cornelia Huck <cohuck(a)redhat.com&gt; > Cc: "Tian, Kevin" <kevin.tian(a)intel.com&gt; > Cc: Zhenyu Wang <zhenyuw(a)linux.intel.com&gt; > Cc: "Wang, Zhi A" <zhi.a.wang(a)intel.com&gt; > c: Neo Jia <cjia(a)nvidia.com&gt; > Cc: Kirti Wankhede <kwankhede(a)nvidia.com&gt; > > Signed-off-by: Yan Zhao <yan.y.zhao(a)intel.com&gt; > --- > drivers/gpu/drm/i915/gvt/Makefile | 2 +- > drivers/gpu/drm/i915/gvt/device_version.c | 94 +++++++++++++++++++++++ > drivers/gpu/drm/i915/gvt/gvt.c | 55 +++++++++++++ > drivers/gpu/drm/i915/gvt/gvt.h | 6 ++ > 4 files changed, 156 insertions(+), 1 deletion(-) > create mode 100644 drivers/gpu/drm/i915/gvt/device_version.c > (...) > +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; > + > + /* first 32 bit common part specifying vendor id and it's a pci > + * device > + */ > + cnt = snprintf(buf, GVT_DEVICE_VERSION_COMMON_LEN + 1, > + "%08x", GVT_VFIO_DEVICE_VENDOR_ID); > + buf += cnt; > + ret += cnt; > + > + /* vendor proprietary part: device id + mdev type */ > + /* device id */ > + cnt = snprintf(buf, GVT_DEVICE_VERSION_DEVICE_ID_LEN + 2, > + "-%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; > +} Looking at this handling, it seems much easier to me to simply use a numeric value instead of a string: You don't have to build it via sprintf, there are generic functions for parsing a string input into a simple number, and you have more options for compatibility (e.g. "version must be between m and n" instead of an exact match). If you still need to encode the device id here, you should be able to easily do something like (device_id << 16) | migration_version -- do you think that could work?

> + > +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; I think the meaning of the error codes should really be standardized across vendor drivers, if we need a value for "this device does not support migration at all". (Your choices look reasonable for that.)

> + > + return 0; > +} > diff --git a/drivers/gpu/drm/i915/gvt/gvt.c b/drivers/gpu/drm/i915/gvt/gvt.c > index 43f4242062dd..e720465b93d8 100644 > --- a/drivers/gpu/drm/i915/gvt/gvt.c > +++ b/drivers/gpu/drm/i915/gvt/gvt.c > @@ -105,14 +105,69 @@ static ssize_t description_show(struct kobject *kobj, struct device *dev, > type->weight); > } > > +static ssize_t version_show(struct kobject *kobj, struct device *dev, > + char *buf) > +{ > +#ifdef GVT_MIGRATION_VERSION > + struct drm_i915_private *i915 = kdev_to_i915(dev); > + const char *mdev_type = kobject_name(kobj); > + > + return intel_gvt_get_vfio_device_version(i915, buf, mdev_type); > +#else > + /* do not support live migration */ > + return -EINVAL; ...but this looks inconsistent. I would expect -ENODEV here, same as for non-gen{8,9}.

Or simply do not create the attribute at all in that case?

> +#endif > +} > + > +static ssize_t version_store(struct kobject *kobj, struct device *dev, > + const char *buf, size_t count) > +{ > +#ifdef GVT_MIGRATION_VERSION > + char *remote = NULL, *self = NULL; > + int len, ret = 0; > + struct drm_i915_private *i915 = kdev_to_i915(dev); > + const char *mdev_type = kobject_name(kobj); > + > + len = intel_gvt_get_vfio_device_version_len(i915); > + if (len < 0) > + return len; > + > + self = kmalloc(len, GFP_KERNEL); > + if (!self) > + return -ENOMEM; > + > + ret = intel_gvt_get_vfio_device_version(i915, self, mdev_type); > + if (ret < 0) > + goto out; > + > + remote = kstrndup(buf, count, GFP_KERNEL); > + if (!remote) { > + ret = -ENOMEM; > + goto out; > + } > + > + ret = intel_gvt_check_vfio_device_version(i915, self, remote); > + > +out: > + kfree(self); > + kfree(remote); > + return (ret < 0 ? ret : count); > +#else > + /* do not support live migration */ > + return -EINVAL; > +#endif > +} > + > static MDEV_TYPE_ATTR_RO(available_instances); > static MDEV_TYPE_ATTR_RO(device_api); > static MDEV_TYPE_ATTR_RO(description); > +static MDEV_TYPE_ATTR_RW(version); > > static struct attribute *gvt_type_attrs[] = { > &mdev_type_attr_available_instances.attr, > &mdev_type_attr_device_api.attr, > &mdev_type_attr_description.attr, > + &mdev_type_attr_version.attr, > NULL, > }; > (...) _______________________________________________ intel-gvt-dev mailing list intel-gvt-dev(a)lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev