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Re: [libvirt] [PATCHv2] nodedev: add switchdev to NIC capabilities



I removed the memset from virNetDevPutExtraHeader and tested on a card supporting switchdev.
It looks fine to me :)
Great review guys, thanks!


-----Original Message-----
From: John Ferlan [mailto:jferlan redhat com] 
Sent: Saturday, September 16, 2017 2:04 PM
To: Laine Stump <laine laine org>; libvir-list redhat com
Cc: Edan David <edand mellanox com>
Subject: Re: [libvirt] [PATCHv2] nodedev: add switchdev to NIC capabilities



On 09/14/2017 11:23 AM, Laine Stump wrote:
> (Almost all of my comments result in "ok, no action needed". There are 
> just three items I would like to see changed (2 trivial, 1 also small 
> but Edan or John may think it prudent to re-test with the change 
> before
> pushing) - I marked those comments with [**].
> 
> On 08/21/2017 05:19 AM, Edan David wrote:
>> Adding functionality to libvirt that will allow querying the 
>> interface for the availability of switchdev Offloading NIC capabilities.
>> The switchdev mode was introduced in kernel 4.8, the iproute2-devlink 
>> command to retrieve the swtichdev NIC feature, Command example:  
>> devlink dev eswitch show pci/0000:03:00.0 This feature is needed for 
>> Openstack so we can do a scheduling decision if the NIC is in 
>> Hardware Offload (switchdev) or regular SR-IOV (legacy) mode.
>> And select the appropriate hypervisors with the requested capability see [1].
>>
>> [1] - 
>> https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsp
>> ecs.openstack.org%2Fopenstack%2Fnova-specs%2Fspecs%2Fpike%2Fapproved%
>> 2Fenable-sriov-nic-features.html&data=02%7C01%7Cedand%40mellanox.com%
>> 7C1e30890a5c7a4f9f045f08d4fcf2b479%7Ca652971c7d2e4d9ba6a4d149256f461b
>> %7C0%7C0%7C636411566714987559&sdata=Ri340H6MLap3HpOMDrb%2FFk6D9agQjEh
>> C9cvR7%2FbV1Ls%3D&reserved=0
>> ---
>>  configure.ac                                      |  13 ++
>>  docs/formatnode.html.in                           |   1 +
>>  src/util/virnetdev.c                              | 187 +++++++++++++++++++++-
>>  src/util/virnetdev.h                              |   1 +
>>  tests/nodedevschemadata/net_00_13_02_b9_f9_d3.xml |   1 +
>>  tests/nodedevschemadata/net_00_15_58_2f_e9_55.xml |   1 +
>>  6 files changed, 203 insertions(+), 1 deletion(-)
>>
>> diff --git a/configure.ac b/configure.ac index b12b7fa..c089798 
>> 100644
>> --- a/configure.ac
>> +++ b/configure.ac
>> @@ -627,6 +627,19 @@ if test "$with_linux" = "yes"; then
>>      AC_CHECK_HEADERS([linux/btrfs.h])  fi
>>  
>> +dnl
>> +dnl check for kernel headers required by devlink dnl if test 
>> +"$with_linux" = "yes"; then
>> +    AC_CHECK_HEADERS([linux/devlink.h])
>> +    AC_CHECK_DECLS([DEVLINK_GENL_VERSION, DEVLINK_GENL_NAME, 
>> +DEVLINK_ATTR_MAX, DEVLINK_CMD_ESWITCH_GET, DEVLINK_ATTR_BUS_NAME, 
>> +DEVLINK_ATTR_DEV_NAME, DEVLINK_ATTR_ESWITCH_MODE, 
>> +DEVLINK_ESWITCH_MODE_SWITCHDEV],
> 
> That's very ..... thorough, and potentially misleading if someone ever 
> wanted to use devlink to check for something other than switchdev (e.g.
> [mythical feature X]) on some system that didn't have the proper stuff 
> defined for switchdev, but did have it for [other mythical feature X].
> But that's all just hypothetical, so this is fine with me.
> 
> 
>> +                   [AC_DEFINE([HAVE_DECL_DEVLINK],
>> +                              [1],
>> +                              [whether devlink declarations is 
>> + available])],
> 
> [**]
> s/is/are/
> 

Yep - altered...

>> +                   [],
>> +                   [[#include <linux/devlink.h>]]) fi
>> +
>>  dnl Allow perl/python overrides
>>  AC_PATH_PROGS([PYTHON], [python2 python])  if test -z "$PYTHON"; 
>> then diff --git a/docs/formatnode.html.in b/docs/formatnode.html.in 
>> index 4d935b5..29244a8 100644
>> --- a/docs/formatnode.html.in
>> +++ b/docs/formatnode.html.in
>> @@ -227,6 +227,7 @@
>>                      <dt><code>rxhash</code></dt><dd>receive-hashing</dd>
>>                      <dt><code>rdma</code></dt><dd>remote-direct-memory-access</dd>
>>                      
>> <dt><code>txudptnl</code></dt><dd>tx-udp-tunnel-segmentation</dd>
>> +                    
>> + <dt><code>switchdev</code></dt><dd>kernel-forward-plane-offload</dd
>> + >
> 
> pretty odd abbreviation. But it is what it is :-)
> >>                  </dl>
>>                </dd>
>>                <dt><code>capability</code></dt> diff --git 
>> a/src/util/virnetdev.c b/src/util/virnetdev.c index 51a6e42..fc7c961 
>> 100644
>> --- a/src/util/virnetdev.c
>> +++ b/src/util/virnetdev.c
>> @@ -59,6 +59,10 @@
>>  # include <net/if_dl.h>
>>  #endif
>>  
>> +#if HAVE_DECL_DEVLINK
>> +# include <linux/devlink.h>
>> +#endif
>> +
>>  #ifndef IFNAMSIZ
>>  # define IFNAMSIZ 16
>>  #endif
>> @@ -2481,7 +2485,8 @@ VIR_ENUM_IMPL(virNetDevFeature,
>>                "ntuple",
>>                "rxhash",
>>                "rdma",
>> -              "txudptnl")
>> +              "txudptnl",
>> +              "switchdev")
>>  
>>  #ifdef __linux__
>>  int
>> @@ -2936,6 +2941,7 @@ int virNetDevGetRxFilter(const char *ifname,
>>      return ret;
>>  }
>>  
>> +
> 
> [**]
> Added a spurious extra line.
> 

Removed.

>>  #if defined(SIOCETHTOOL) && defined(HAVE_STRUCT_IFREQ)
>>  
>>  /**
>> @@ -3115,6 +3121,182 @@ virNetDevGetEthtoolFeatures(virBitmapPtr 
>> bitmap,  }
>>  
>>  
>> +#if HAVE_DECL_DEVLINK
>> +/**
>> + * virNetDevPutExtraHeader
>> + * reserve and prepare room for an extra header
>> + * This function sets to zero the room that is required to put the 
>> +extra
>> + * header after the initial Netlink header. This function also 
>> +increases
>> + * the nlmsg_len field.
>> + *
>> + * @nlh: pointer to Netlink header
>> + * @size: size of the extra header that we want to put
>> + *
>> + * Returns pointer to the start of the extended header  */ static 
>> +void * virNetDevPutExtraHeader(struct nlmsghdr *nlh,
>> +                        size_t size) {
>> +    char *ptr = (char *)nlh + nlh->nlmsg_len;
>> +    size_t len = NLMSG_ALIGN(size);
>> +    nlh->nlmsg_len += len;
>> +    memset(ptr, 0, len);
> 
> [**]
> I'm fairly confident this memset() is unnecessary. The buffer the 
> "extra header" is being added to is allocated with 
> nlmsg_alloc_simple(); I looked at the source for nlmsg_alloc_simple(), 
> and it ends up calling calloc(), which will initialize everything to 0 
> anyway (and any important fields are set to some other value 
> immediately after return from virNetDevPutExtraHeader()). The reason 
> the extra memset() bothers me is that 1) we don't set memory allocated 
> for netlink messages to 0 anywhere else in our netlink-related code so 
> it's inconsistent, and 2) having an extra memset(0) when it's not 
> needed could end up becoming the start of a "cargo cult" practice of 
> calling memset(0) all over the place just because we're paranoid - I'd 
> rather avoid extra initialization if it's redundant/superfluous.
> 
> I of course wouldn't want this to be pushed with such a change without 
> having it tested. I did make this change locally and ran it under gdb 
> with a breakpoint on virNetDevPutExtraHeader(), and saw that the 
> entire
> 4096 bytes of *nl_msg is initialized to 0; it's up to you whether or 
> not you think it's necessary to re-test on a system that has a card 
> that support switchdev.
> 
> (alternately, John could push it as is, and I could send a separate 
> patch removing the memset(), which could be ACKed by Edan after he 
> tries it (or NACKed in the event that I'm completely wrong about it 
> :-)
> 

I saw this on my initial review and thought perhaps it was superfluous.
Tracing through various code to find the original calloc is impressive!
I didn't originally do anything with it because I didn't think it would hurt, but I agree with you.

So I've removed it from my local copy of the patch that I'll use to push on Monday. Perhaps by then Edan will see these messages and be able to indicate one way or another whether it should be kept from a "retest"
POV.  Besides, if anything breaks in one of the many CI builds, I don't want to spent weekend hours trying to clean up after it.


John

>> +    return ptr;
>> +}
> 
> I *was* going to say this doesn't need to be inside HAVE_DECL_DEVLINK, 
> but since it's defined as static, and only used by a function that is 
> itself inside HAVE_DECL_DEVLINK, this placement is correct.
> 
> 
>> +
>> +
>> +/**
>> + * virNetDevGetFamilyId:
>> + * This function supplies the devlink family id
>> + *
>> + * @family_name: the name of the family to query
>> + *
>> + * Returns family id or 0 on failure.
>> + */
>> +static uint32_t
>> +virNetDevGetFamilyId(const char *family_name) {
>> +    struct nl_msg *nl_msg = NULL;
>> +    struct nlmsghdr *resp = NULL;
>> +    struct genlmsghdr* gmsgh = NULL;
>> +    struct nlattr *tb[CTRL_ATTR_MAX + 1] = {NULL, };
>> +    unsigned int recvbuflen;
>> +    uint32_t family_id = 0;
>> +
>> +    if (!(nl_msg = nlmsg_alloc_simple(GENL_ID_CTRL,
>> +                                      NLM_F_REQUEST | NLM_F_ACK))) {
>> +        virReportOOMError();
>> +        goto cleanup;
>> +    }
>> +
>> +    if (!(gmsgh = virNetDevPutExtraHeader(nlmsg_hdr(nl_msg), sizeof(struct genlmsghdr))))
>> +        goto cleanup;
>> +
>> +    gmsgh->cmd = CTRL_CMD_GETFAMILY;
>> +    gmsgh->version = DEVLINK_GENL_VERSION;
>> +
>> +    if (nla_put_string(nl_msg, CTRL_ATTR_FAMILY_NAME, family_name) < 0) {
>> +        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> +                       _("allocated netlink buffer is too small"));
>> +        goto cleanup;
>> +    }
>> +
>> +    if (virNetlinkCommand(nl_msg, &resp, &recvbuflen, 0, 0, NETLINK_GENERIC, 0) < 0)
>> +        goto cleanup;
>> +
>> +    if (nlmsg_parse(resp, sizeof(struct nlmsghdr), tb, CTRL_CMD_MAX, NULL) < 0) {
>> +        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> +                       _("malformed netlink response message"));
>> +        goto cleanup;
>> +    }
>> +
>> +    if (tb[CTRL_ATTR_FAMILY_ID] == NULL)
>> +        goto cleanup;
>> +
>> +    family_id = *(uint32_t *)RTA_DATA(tb[CTRL_ATTR_FAMILY_ID]);
>> +
>> + cleanup:
>> +    nlmsg_free(nl_msg);
>> +    VIR_FREE(resp);
>> +    return family_id;
>> +}
>> +
>> +
>> +/**
>> + * virNetDevSwitchdevFeature
>> + * This function checks for the availability of Switchdev feature
>> + * and add it to bitmap
>> + *
>> + * @ifname: name of the interface
>> + * @out: add Switchdev feature if exist to bitmap
>> + *
>> + * Returns 0 on success, -1 on failure.
>> + */
>> +static int
>> +virNetDevSwitchdevFeature(const char *ifname,
>> +                          virBitmapPtr *out) {
>> +    struct nl_msg *nl_msg = NULL;
>> +    struct nlmsghdr *resp = NULL;
>> +    unsigned int recvbuflen;
>> +    struct nlattr *tb[DEVLINK_ATTR_MAX + 1] = {NULL, };
>> +    virPCIDevicePtr pci_device_ptr = NULL;
>> +    struct genlmsghdr* gmsgh = NULL;
>> +    const char *pci_name;
>> +    char *pfname = NULL;
>> +    int is_vf = -1;
>> +    int ret = -1;
>> +    uint32_t family_id;
>> +
>> +    if ((family_id = virNetDevGetFamilyId(DEVLINK_GENL_NAME)) <= 0)
>> +        return ret;
>> +
>> +    if ((is_vf = virNetDevIsVirtualFunction(ifname)) < 0)
>> +        return ret;
>> +
>> +    if (is_vf == 1 && virNetDevGetPhysicalFunction(ifname, &pfname) < 0)
>> +        goto cleanup;
>> +
>> +    if (!(nl_msg = nlmsg_alloc_simple(family_id,
>> +                                      NLM_F_REQUEST | NLM_F_ACK))) {
>> +        virReportOOMError();
>> +        goto cleanup;
>> +    }
>> +
>> +    if (!(gmsgh = virNetDevPutExtraHeader(nlmsg_hdr(nl_msg), sizeof(struct genlmsghdr))))
>> +        goto cleanup;
>> +
>> +    gmsgh->cmd = DEVLINK_CMD_ESWITCH_GET;
>> +    gmsgh->version = DEVLINK_GENL_VERSION;
>> +
>> +    pci_device_ptr = pfname ? virNetDevGetPCIDevice(pfname) :
>> +                              virNetDevGetPCIDevice(ifname);
>> +    if (pci_device_ptr == NULL)
>> +        goto cleanup;
>> +
>> +    pci_name = virPCIDeviceGetName(pci_device_ptr);
>> +
>> +    if (nla_put(nl_msg, DEVLINK_ATTR_BUS_NAME, strlen("pci")+1, "pci") < 0 ||
>> +        nla_put(nl_msg, DEVLINK_ATTR_DEV_NAME, strlen(pci_name)+1, pci_name) < 0) {
>> +        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> +                       _("allocated netlink buffer is too small"));
>> +        goto cleanup;
>> +    }
>> +
>> +    if (virNetlinkCommand(nl_msg, &resp, &recvbuflen, 0, 0, NETLINK_GENERIC, 0) < 0)
>> +        goto cleanup;
>> +
>> +    if (nlmsg_parse(resp, sizeof(struct genlmsghdr), tb, DEVLINK_ATTR_MAX, NULL) < 0) {
>> +        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> +                       _("malformed netlink response message"));
>> +        goto cleanup;
>> +    }
>> +
>> +    if (tb[DEVLINK_ATTR_ESWITCH_MODE] &&
>> +        *(int *)RTA_DATA(tb[DEVLINK_ATTR_ESWITCH_MODE]) == DEVLINK_ESWITCH_MODE_SWITCHDEV) {
>> +        ignore_value(virBitmapSetBit(*out, VIR_NET_DEV_FEAT_SWITCHDEV));
>> +    }
> 
> 
> I won't pretend that I know all about these particular netlink 
> messages/attributes. I can say that the code all looks similar to our 
> other netlink code, and when I run it on my host that doesn't have 
> cards supporting switchdev, it does execute this code and reports no 
> switchdev capability in the nodedev-dumpxml output of my NICs; since 
> I'm sure Edan has done the same test on a system that *does* have 
> switchdev-capable NICs, I'd say that's adequate testing.
> 
> Based on that I give my ACK (with at least the two trivial [**] items 
> changed, preferably also memset() removed), or if you prefer:
> 
> Reviewed-by: Laine Stump <laine laine org>
> 
> 
> 
>> +
>> +    ret = 0;
>> +
>> + cleanup:
>> +    nlmsg_free(nl_msg);
>> +    virPCIDeviceFree(pci_device_ptr);
>> +    VIR_FREE(resp);
>> +    VIR_FREE(pfname);
>> +    return ret;
>> +}
>> +#else
>> +static int
>> +virNetDevSwitchdevFeature(const char *ifname ATTRIBUTE_UNUSED,
>> +                          virBitmapPtr *out ATTRIBUTE_UNUSED) {
>> +    return 0;
>> +}
>> +#endif
>> +
>> +
>>  # if HAVE_DECL_ETHTOOL_GFEATURES
>>  /**
>>   * virNetDevGFeatureAvailable
>> @@ -3315,6 +3497,9 @@ virNetDevGetFeatures(const char *ifname,
>>      if (virNetDevRDMAFeature(ifname, out) < 0)
>>          goto cleanup;
>>  
>> +    if (virNetDevSwitchdevFeature(ifname, out) < 0)
>> +        goto cleanup;
>> +
>>      ret = 0;
>>   cleanup:
>>      VIR_FORCE_CLOSE(fd);
>> diff --git a/src/util/virnetdev.h b/src/util/virnetdev.h index 
>> 9205c0e..71eaf45 100644
>> --- a/src/util/virnetdev.h
>> +++ b/src/util/virnetdev.h
>> @@ -112,6 +112,7 @@ typedef enum {
>>      VIR_NET_DEV_FEAT_RXHASH,
>>      VIR_NET_DEV_FEAT_RDMA,
>>      VIR_NET_DEV_FEAT_TXUDPTNL,
>> +    VIR_NET_DEV_FEAT_SWITCHDEV,
>>      VIR_NET_DEV_FEAT_LAST
>>  } virNetDevFeature;
>>  
>> diff --git a/tests/nodedevschemadata/net_00_13_02_b9_f9_d3.xml 
>> b/tests/nodedevschemadata/net_00_13_02_b9_f9_d3.xml
>> index d4c96e8..88252e6 100644
>> --- a/tests/nodedevschemadata/net_00_13_02_b9_f9_d3.xml
>> +++ b/tests/nodedevschemadata/net_00_13_02_b9_f9_d3.xml
>> @@ -15,6 +15,7 @@
>>      <feature name='rxhash'/>
>>      <feature name='rdma'/>
>>      <feature name='txudptnl'/>
>> +    <feature name='switchdev'/>
>>      <capability type='80211'/>
>>    </capability>
>>  </device>
>> diff --git a/tests/nodedevschemadata/net_00_15_58_2f_e9_55.xml 
>> b/tests/nodedevschemadata/net_00_15_58_2f_e9_55.xml
>> index 71bf90e..f77dfcc 100644
>> --- a/tests/nodedevschemadata/net_00_15_58_2f_e9_55.xml
>> +++ b/tests/nodedevschemadata/net_00_15_58_2f_e9_55.xml
>> @@ -15,6 +15,7 @@
>>      <feature name='rxhash'/>
>>      <feature name='rdma'/>
>>      <feature name='txudptnl'/>
>> +    <feature name='switchdev'/>
>>      <capability type='80203'/>
>>    </capability>
>>  </device>
> 
> 


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