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[87.10.72.39]) by smtp.gmail.com with ESMTPSA id gn26sm418635ejc.14.2021.11.05.01.04.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Nov 2021 01:04:57 -0700 (PDT) Date: Fri, 5 Nov 2021 09:04:54 +0100 From: Stefano Garzarella To: Jason Wang Cc: virtualization , Parav Pandit , "Michael S. Tsirkin" , linux-kernel Subject: Re: [PATCH] vdpa: add driver_override support Message-ID: <20211105080454.wpvtwa7el45kayem@steredhat> References: <20211104161729.258294-1-sgarzare@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 05, 2021 at 11:01:30AM +0800, Jason Wang wrote: >On Fri, Nov 5, 2021 at 12:17 AM Stefano Garzarella wrote: >> >> `driver_override` allows to control which of the vDPA bus drivers >> binds to a vDPA device. >> >> If `driver_override` is not set, the previous behaviour is followed: >> devices use the first vDPA bus driver loaded (unless auto binding >> is disabled). >> >> Tested on Fedora 34 with driverctl(8): >> $ modprobe virtio-vdpa >> $ modprobe vhost-vdpa >> $ modprobe vdpa-sim-net >> >> $ vdpa dev add mgmtdev vdpasim_net name dev1 >> >> # dev1 is attached to the first vDPA bus driver loaded >> $ driverctl -b vdpa list-devices >> dev1 virtio_vdpa >> >> $ driverctl -b vdpa set-override dev1 vhost_vdpa >> >> $ driverctl -b vdpa list-devices >> dev1 vhost_vdpa [*] >> >> Note: driverctl(8) integrates with udev so the binding is >> preserved. >> >> Suggested-by: Jason Wang >> Signed-off-by: Stefano Garzarella >> --- >> include/linux/vdpa.h | 2 ++ >> drivers/vdpa/vdpa.c | 74 ++++++++++++++++++++++++++++++++++++++++++++ >> 2 files changed, 76 insertions(+) >> >> diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h >> index c3011ccda430..ae34015b37b7 100644 >> --- a/include/linux/vdpa.h >> +++ b/include/linux/vdpa.h >> @@ -64,6 +64,7 @@ struct vdpa_mgmt_dev; >> * struct vdpa_device - representation of a vDPA device >> * @dev: underlying device >> * @dma_dev: the actual device that is performing DMA >> + * @driver_override: driver name to force a match > >This seems useless? I'm a bit lost, do you mean we should remove the documentation of `driver_override`? > >> * @config: the configuration ops for this device. >> * @cf_mutex: Protects get and set access to configuration layout. >> * @index: device index >> @@ -76,6 +77,7 @@ struct vdpa_mgmt_dev; >> struct vdpa_device { >> struct device dev; >> struct device *dma_dev; >> + const char *driver_override; >> const struct vdpa_config_ops *config; >> struct mutex cf_mutex; /* Protects get/set config */ >> unsigned int index; >> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c >> index 7332a74a4b00..659231bbfee8 100644 >> --- a/drivers/vdpa/vdpa.c >> +++ b/drivers/vdpa/vdpa.c >> @@ -52,8 +52,81 @@ static void vdpa_dev_remove(struct device *d) >> drv->remove(vdev); >> } >> >> +static int vdpa_dev_match(struct device *dev, struct device_driver *drv) >> +{ >> + struct vdpa_device *vdev = dev_to_vdpa(dev); >> + >> + /* Check override first, and if set, only use the named driver */ >> + if (vdev->driver_override) >> + return strcmp(vdev->driver_override, drv->name) == 0; >> + >> + /* Currently devices must be supported by all vDPA bus >> drivers */ >> + return 1; >> +} >> + >> +static ssize_t driver_override_store(struct device *dev, >> + struct device_attribute *attr, >> + const char *buf, size_t count) >> +{ >> + struct vdpa_device *vdev = dev_to_vdpa(dev); >> + const char *driver_override, *old; >> + char *cp; >> + >> + /* We need to keep extra room for a newline */ >> + if (count >= (PAGE_SIZE - 1)) >> + return -EINVAL; >> + >> + driver_override = kstrndup(buf, count, GFP_KERNEL); >> + if (!driver_override) >> + return -ENOMEM; >> + >> + cp = strchr(driver_override, '\n'); >> + if (cp) >> + *cp = '\0'; >> + >> + device_lock(dev); >> + old = vdev->driver_override; >> + if (strlen(driver_override)) { >> + vdev->driver_override = driver_override; >> + } else { >> + kfree(driver_override); >> + vdev->driver_override = NULL; >> + } >> + device_unlock(dev); >> + >> + kfree(old); >> + >> + return count; >> +} >> + >> +static ssize_t driver_override_show(struct device *dev, >> + struct device_attribute *attr, char *buf) >> +{ >> + struct vdpa_device *vdev = dev_to_vdpa(dev); >> + ssize_t len; >> + >> + device_lock(dev); >> + len = snprintf(buf, PAGE_SIZE, "%s\n", vdev->driver_override); >> + device_unlock(dev); >> + >> + return len; >> +} >> +static DEVICE_ATTR_RW(driver_override); >> + >> +static struct attribute *vdpa_dev_attrs[] = { >> + &dev_attr_driver_override.attr, >> + NULL, >> +}; >> + >> +static const struct attribute_group vdpa_dev_group = { >> + .attrs = vdpa_dev_attrs, >> +}; >> +__ATTRIBUTE_GROUPS(vdpa_dev); >> + >> static struct bus_type vdpa_bus = { >> .name = "vdpa", >> + .dev_groups = vdpa_dev_groups, > >This reminds me that we probably need to document the sysfs interface >in Documentation/ABI/testing/sysfs-bus-vdpa. > Yeah, I'd like to add more documentation. We should also document the device life cycle and management API. It's on my to-do list, I'm prioritizing it! >But it's not the fault of this patch which look good. Thanks, Stefano