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Date: Fri, 22 Jul 2022 08:26:09 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Jacob Keller <jacob.e.keller@...el.com>
Cc: netdev@...r.kernel.org, Jonathan Corbet <corbet@....net>,
Jiri Pirko <jiri@...dia.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Tony Nguyen <anthony.l.nguyen@...el.com>,
David Ahern <dsahern@...nel.org>,
Stephen Hemminger <stephen@...workplumber.org>,
linux-doc@...r.kernel.org, intel-wired-lan@...ts.osuosl.org
Subject: Re: [net-next v2 1/2] devlink: add dry run attribute to flash update
Thu, Jul 21, 2022 at 11:14:46PM CEST, jacob.e.keller@...el.com wrote:
>Users use the devlink flash interface to request a device driver program or
>update the device flash chip. In some cases, a user (or script) may want to
>verify that a given flash update command is supported without actually
>committing to immediately updating the device. For example, a system
>administrator may want to validate that a particular flash binary image
>will be accepted by the device, or simply validate a command before finally
>committing to it.
>
>The current flash update interface lacks a method to support such a dry
>run. Add a new DEVLINK_ATTR_DRY_RUN attribute which shall be used by a
>devlink command to indicate that a request is a dry run which should not
>perform device configuration. Instead, the command should report whether
>the command or configuration request is valid.
>
>While we can validate the initial arguments of the devlink command, a
>proper dry run must be processed by the device driver. This is required
>because only the driver can perform validation of the flash binary file.
>
>Add a new dry_run parameter to the devlink_flash_update_params struct,
>along with the associated bit to indicate if a driver supports verifying a
>dry run.
>
>We always check the dry run attribute last in order to allow as much
>verification of other parameters as possible. For example, even if a driver
>does not support the dry_run option, we can still validate the other
>optional parameters such as the overwrite_mask and per-component update
>name.
>
>Document that userspace should take care when issuing a dry run to older
>kernels, as the flash update command is not strictly verified. Thus,
>unknown attributes will be ignored and this could cause a request for a dry
>run to perform an actual update. We can't fix old kernels to verify unknown
>attributes, but userspace can check the maximum attribute and reject the
>dry run request if it is not supported by the kernel.
>
>Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
>---
>
>Changes since v1:
>* Add kernel doc comments to devlink_flash_update_params
>* Reduce indentation by using nla_get_flag
>
> .../networking/devlink/devlink-flash.rst | 23 +++++++++++++++++++
> include/net/devlink.h | 4 ++++
> include/uapi/linux/devlink.h | 8 +++++++
> net/core/devlink.c | 17 +++++++++++++-
> 4 files changed, 51 insertions(+), 1 deletion(-)
>
>diff --git a/Documentation/networking/devlink/devlink-flash.rst b/Documentation/networking/devlink/devlink-flash.rst
>index 603e732f00cc..1dc373229a54 100644
>--- a/Documentation/networking/devlink/devlink-flash.rst
>+++ b/Documentation/networking/devlink/devlink-flash.rst
>@@ -44,6 +44,29 @@ preserved across the update. A device may not support every combination and
> the driver for such a device must reject any combination which cannot be
> faithfully implemented.
>
>+Dry run
>+=======
>+
>+Users can request a "dry run" of a flash update by adding the
>+``DEVLINK_ATTR_DRY_RUN`` attribute to the ``DEVLINK_CMD_FLASH_UPDATE``
>+command. If the attribute is present, the kernel will only verify that the
>+provided command is valid. During a dry run, an update is not performed.
>+
>+If supported by the driver, the flash image contents are also validated and
>+the driver may indicate whether the file is a valid flash image for the
>+device.
>+
>+.. code:: shell
>+
>+ $ devlink dev flash pci/0000:af:00.0 file image.bin dry-run
>+ Validating flash binary
>+
>+Note that user space should take care when adding this attribute. Older
>+kernels which do not recognize the attribute may accept the command with an
>+unknown attribute. This could lead to a request for a dry run which performs
>+an unexpected update. To avoid this, user space should check the policy dump
>+and verify that the attribute is recognized before adding it to the command.
>+
> Firmware Loading
> ================
>
>diff --git a/include/net/devlink.h b/include/net/devlink.h
>index 780744b550b8..47b86ccb85b0 100644
>--- a/include/net/devlink.h
>+++ b/include/net/devlink.h
>@@ -613,6 +613,8 @@ enum devlink_param_generic_id {
> * struct devlink_flash_update_params - Flash Update parameters
> * @fw: pointer to the firmware data to update from
> * @component: the flash component to update
>+ * @overwrite_mask: what sections of flash can be overwritten
Well, strictly speaking, this is not related to this patch and should be
done in a separate one. But hey, it's a comment, so I guess noone really
cares.
>+ * @dry_run: if true, do not actually update the flash
> *
> * With the exception of fw, drivers must opt-in to parameters by
> * setting the appropriate bit in the supported_flash_update_params field in
>@@ -622,10 +624,12 @@ struct devlink_flash_update_params {
> const struct firmware *fw;
> const char *component;
> u32 overwrite_mask;
>+ bool dry_run;
> };
>
> #define DEVLINK_SUPPORT_FLASH_UPDATE_COMPONENT BIT(0)
> #define DEVLINK_SUPPORT_FLASH_UPDATE_OVERWRITE_MASK BIT(1)
>+#define DEVLINK_SUPPORT_FLASH_UPDATE_DRY_RUN BIT(2)
>
> struct devlink_region;
> struct devlink_info_req;
>diff --git a/include/uapi/linux/devlink.h b/include/uapi/linux/devlink.h
>index b3d40a5d72ff..e24a5a808a12 100644
>--- a/include/uapi/linux/devlink.h
>+++ b/include/uapi/linux/devlink.h
>@@ -576,6 +576,14 @@ enum devlink_attr {
> DEVLINK_ATTR_LINECARD_TYPE, /* string */
> DEVLINK_ATTR_LINECARD_SUPPORTED_TYPES, /* nested */
>
>+ /* Before adding this attribute to a command, user space should check
>+ * the policy dump and verify the kernel recognizes the attribute.
>+ * Otherwise older kernels which do not recognize the attribute may
>+ * silently accept the unknown attribute while not actually performing
>+ * a dry run.
>+ */
>+ DEVLINK_ATTR_DRY_RUN, /* flag */
>+
> /* add new attributes above here, update the policy in devlink.c */
>
> __DEVLINK_ATTR_MAX,
>diff --git a/net/core/devlink.c b/net/core/devlink.c
>index 98d79feeb3dc..1cff636c9b2b 100644
>--- a/net/core/devlink.c
>+++ b/net/core/devlink.c
>@@ -4743,7 +4743,8 @@ EXPORT_SYMBOL_GPL(devlink_flash_update_timeout_notify);
> static int devlink_nl_cmd_flash_update(struct sk_buff *skb,
> struct genl_info *info)
> {
>- struct nlattr *nla_component, *nla_overwrite_mask, *nla_file_name;
>+ struct nlattr *nla_component, *nla_overwrite_mask, *nla_file_name,
>+ *nla_dry_run;
> struct devlink_flash_update_params params = {};
> struct devlink *devlink = info->user_ptr[0];
> const char *file_name;
>@@ -4789,6 +4790,19 @@ static int devlink_nl_cmd_flash_update(struct sk_buff *skb,
> return ret;
> }
>
>+ /* Always check dry run last, in order to allow verification of other
>+ * parameter support even if the particular driver does not yet
>+ * support a full dry-run
>+ */
>+ params.dry_run = nla_get_flag(info->attrs[DEVLINK_ATTR_DRY_RUN]);
>+ if (params.dry_run &&
>+ !(supported_params & DEVLINK_SUPPORT_FLASH_UPDATE_DRY_RUN)) {
>+ NL_SET_ERR_MSG_ATTR(info->extack, nla_dry_run,
>+ "flash update is supported, but dry run is not supported for this device");
>+ release_firmware(params.fw);
>+ return -EOPNOTSUPP;
>+ }
>+
> devlink_flash_update_begin_notify(devlink);
> ret = devlink->ops->flash_update(devlink, ¶ms, info->extack);
> devlink_flash_update_end_notify(devlink);
>@@ -9004,6 +9018,7 @@ static const struct nla_policy devlink_nl_policy[DEVLINK_ATTR_MAX + 1] = {
> [DEVLINK_ATTR_RATE_PARENT_NODE_NAME] = { .type = NLA_NUL_STRING },
> [DEVLINK_ATTR_LINECARD_INDEX] = { .type = NLA_U32 },
> [DEVLINK_ATTR_LINECARD_TYPE] = { .type = NLA_NUL_STRING },
>+ [DEVLINK_ATTR_DRY_RUN] = { .type = NLA_FLAG },
> };
>
> static const struct genl_small_ops devlink_nl_ops[] = {
>--
>2.35.1.456.ga9c7032d4631
>
Reviewed-by: Jiri Pirko <jiri@...dia.com>
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