Re: [PATCH 2/2] [NOT-FOR-MERGE] Add qtest for migration over RDMA

[Fabiano Rosas <farosas@suse.de>]

Peter Xu <peterx@redhat.com> writes:

> On Wed, Feb 19, 2025 at 05:33:26AM +0000, Zhijian Li (Fujitsu) wrote:
>> 
>> 
>> On 19/02/2025 06:40, Peter Xu wrote:
>> > On Tue, Feb 18, 2025 at 06:03:48PM -0300, Fabiano Rosas wrote:
>> >> Li Zhijian via <qemu-devel@nongnu.org> writes:
>> >>
>> >>> This qtest requirs there is RXE link in the host.
>> >>>
>> >>> Here is an example to show how to add this RXE link:
>> >>> $ ./new-rdma-link.sh
>> >>> 192.168.22.93
>> >>>
>> >>> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
>> >>> ---
>> >>> The RDMA migration was broken again...due to lack of sufficient test/qtest.
>> >>>
>> >>> It's urgly to add and execute a script to establish an RDMA link in
>> >>> the C program. If anyone has a better suggestion, please let me know.
>> >>>
>> >>> $ cat ./new-rdma-link.sh
>> >>> get_ipv4_addr() {
>> >>>          ip -4 -o addr show dev "$1" |
>> >>>                  sed -n 's/.*[[:blank:]]inet[[:blank:]]*\([^[:blank:]/]*\).*/\1/p'
>> >>> }
>> >>>
>> >>> has_soft_rdma() {
>> >>>          rdma link | grep -q " netdev $1[[:blank:]]*\$"
>> >>> }
>> >>>
>> >>> start_soft_rdma() {
>> >>>          local type
>> >>>
>> >>>          modprobe rdma_rxe || return $?
>> >>>          type=rxe
>> >>>          (
>> >>>                  cd /sys/class/net &&
>> >>>                          for i in *; do
>> >>>                                  [ -e "$i" ] || continue
>> >>>                                  [ "$i" = "lo" ] && continue
>> >>>                                  [ "$(<"$i/addr_len")" = 6 ] || continue
>> >>>                                  [ "$(<"$i/carrier")" = 1 ] || continue
>> >>>                                  has_soft_rdma "$i" && break
>> >>>                                  rdma link add "${i}_$type" type $type netdev "$i" && break
>> >>>                          done
>> >>>                  has_soft_rdma "$i" && echo $i
>> >>>          )
>> >>>
>> >>> }
>> >>>
>> >>> rxe_link=$(start_soft_rdma)
>> >>> [[ "$rxe_link" ]] && get_ipv4_addr $rxe_link
>> >>>
>> >>> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
>> >>> ---
>> >>>   tests/qtest/migration/new-rdma-link.sh |  34 ++++++++
>> >>>   tests/qtest/migration/precopy-tests.c  | 103 +++++++++++++++++++++++++
>> >>>   2 files changed, 137 insertions(+)
>> >>>   create mode 100644 tests/qtest/migration/new-rdma-link.sh
>> >>>
>> >>> diff --git a/tests/qtest/migration/new-rdma-link.sh b/tests/qtest/migration/new-rdma-link.sh
>> >>> new file mode 100644
>> >>> index 00000000000..ca20594eaae
>> >>> --- /dev/null
>> >>> +++ b/tests/qtest/migration/new-rdma-link.sh
>> >>> @@ -0,0 +1,34 @@
>> >>> +#!/bin/bash
>> >>> +
>> >>> +# Copied from blktests
>> >>> +get_ipv4_addr() {
>> >>> +	ip -4 -o addr show dev "$1" |
>> >>> +		sed -n 's/.*[[:blank:]]inet[[:blank:]]*\([^[:blank:]/]*\).*/\1/p'
>> >>> +}
>> >>> +
>> >>> +has_soft_rdma() {
>> >>> +	rdma link | grep -q " netdev $1[[:blank:]]*\$"
>> >>> +}
>> >>> +
>> >>> +start_soft_rdma() {
>> >>> +	local type
>> >>> +
>> >>> +	modprobe rdma_rxe || return $?
>> >>> +	type=rxe
>> >>> +	(
>> >>> +		cd /sys/class/net &&
>> >>> +			for i in *; do
>> >>> +				[ -e "$i" ] || continue
>> >>> +				[ "$i" = "lo" ] && continue
>> >>> +				[ "$(<"$i/addr_len")" = 6 ] || continue
>> >>> +				[ "$(<"$i/carrier")" = 1 ] || continue
>> >>> +				has_soft_rdma "$i" && break
>> >>> +				rdma link add "${i}_$type" type $type netdev "$i" && break
>> >>> +			done
>> >>> +		has_soft_rdma "$i" && echo $i
>> >>> +	)
>> >>> +
>> >>> +}
>> >>> +
>> >>> +rxe_link=$(start_soft_rdma)
>> >>> +[[ "$rxe_link" ]] && get_ipv4_addr $rxe_link
>> >>> diff --git a/tests/qtest/migration/precopy-tests.c b/tests/qtest/migration/precopy-tests.c
>> >>> index 162fa695318..d2a1c9c9438 100644
>> >>> --- a/tests/qtest/migration/precopy-tests.c
>> >>> +++ b/tests/qtest/migration/precopy-tests.c
>> >>> @@ -98,6 +98,105 @@ static void test_precopy_unix_dirty_ring(void)
>> >>>       test_precopy_common(&args);
>> >>>   }
>> >>>   
>> >>> +static int new_rdma_link(char *buffer) {
>> >>> +    // Copied from blktests
>> >>> +    const char *script =
>> >>> +        "#!/bin/bash\n"
>> >>> +        "\n"
>> >>> +        "get_ipv4_addr() {\n"
>> >>> +        "    ip -4 -o addr show dev \"$1\" |\n"
>> >>> +        "    sed -n 's/.*[[:blank:]]inet[[:blank:]]*\\([^[:blank:]/]*\\).*/\\1/p'\n"
>> >>> +        "}\n"
>> >>> +        "\n"
>> >>> +        "has_soft_rdma() {\n"
>> >>> +        "    rdma link | grep -q \" netdev $1[[:blank:]]*\\$\"\n"
>> >>> +        "}\n"
>> >>> +        "\n"
>> >>> +        "start_soft_rdma() {\n"
>> >>> +        "    local type\n"
>> >>> +        "\n"
>> >>> +        "    modprobe rdma_rxe || return $?\n"
>> >>> +        "    type=rxe\n"
>> >>> +        "    (\n"
>> >>> +        "        cd /sys/class/net &&\n"
>> >>> +        "        for i in *; do\n"
>> >>> +        "            [ -e \"$i\" ] || continue\n"
>> >>> +        "            [ \"$i\" = \"lo\" ] && continue\n"
>> >>> +        "            [ \"$(<$i/addr_len)\" = 6 ] || continue\n"
>> >>> +        "            [ \"$(<$i/carrier)\" = 1 ] || continue\n"
>> >>> +        "            has_soft_rdma \"$i\" && break\n"
>> >>> +        "            rdma link add \"${i}_$type\" type $type netdev \"$i\" && break\n"
>> >>> +        "        done\n"
>> >>> +        "        has_soft_rdma \"$i\" && echo $i\n"
>> >>> +        "    )\n"
>> >>> +        "}\n"
>> >>> +        "\n"
>> >>> +        "rxe_link=$(start_soft_rdma)\n"
>> >>> +        "[[ \"$rxe_link\" ]] && get_ipv4_addr $rxe_link\n";
>> >>> +
>> >>> +    char script_filename[] = "/tmp/temp_scriptXXXXXX";
>> >>> +    int fd = mkstemp(script_filename);
>> >>> +    if (fd == -1) {
>> >>> +        perror("Failed to create temporary file");
>> >>> +        return 1;
>> >>> +    }
>> >>> +
>> >>> +    FILE *fp = fdopen(fd, "w");
>> >>> +    if (fp == NULL) {
>> >>> +        perror("Failed to open file stream");
>> >>> +        close(fd);
>> >>> +        return 1;
>> >>> +    }
>> >>> +    fprintf(fp, "%s", script);
>> >>> +    fclose(fp);
>> >>> +
>> >>> +    if (chmod(script_filename, 0700) == -1) {
>> >>> +        perror("Failed to set execute permission");
>> >>> +        return 1;
>> >>> +    }
>> >>> +
>> >>> +    FILE *pipe = popen(script_filename, "r");
>> >>> +    if (pipe == NULL) {
>> >>> +        perror("Failed to run script");
>> >>> +        return 1;
>> >>> +    }
>> >>> +
>> >>> +    int idx = 0;
>> >>> +    while (fgets(buffer + idx, 128 - idx, pipe) != NULL) {
>> >>> +        idx += strlen(buffer);
>> >>> +    }
>> >>> +    if (buffer[idx - 1] == '\n')
>> >>> +        buffer[idx - 1] = 0;
>> >>> +
>> >>> +    int status = pclose(pipe);
>> >>> +    if (status == -1) {
>> >>> +        perror("Error reported by pclose()");
>> >>> +    } else if (!WIFEXITED(status)) {
>> >>> +        printf("Script did not terminate normally\n");
>> >>> +    }
>> >>> +
>> >>> +    remove(script_filename);
>> > 
>> > The script can be put separately instead if hard-coded here, right?
>> 
>> 
>> Sure, If so, I wonder whether the migration-test program is able to know where is this script?
>> 
>> 
>> > 
>> >>> +
>> >>> +    return 0;
>> >>> +}
>> >>> +
>> >>> +static void test_precopy_rdma_plain(void)
>> >>> +{
>> >>> +    char buffer[128] = {};
>> >>> +
>> >>> +    if (new_rdma_link(buffer))
>> >>> +        return;
>> >>> +
>> >>> +    g_autofree char *uri = g_strdup_printf("rdma:%s:7777", buffer);
>> >>> +
>> >>> +    MigrateCommon args = {
>> >>> +        .listen_uri = uri,
>> >>> +        .connect_uri = uri,
>> >>> +    };
>> >>> +
>> >>> +    test_precopy_common(&args);
>> >>> +}
>> >>> +
>> >>>   static void test_precopy_tcp_plain(void)
>> >>>   {
>> >>>       MigrateCommon args = {
>> >>> @@ -968,6 +1067,10 @@ static void migration_test_add_precopy_smoke(MigrationTestEnv *env)
>> >>>                          test_multifd_tcp_uri_none);
>> >>>       migration_test_add("/migration/multifd/tcp/plain/cancel",
>> >>>                          test_multifd_tcp_cancel);
>> >>> +#ifdef CONFIG_RDMA
>> >>> +    migration_test_add("/migration/precopy/rdma/plain",
>> >>> +                       test_precopy_rdma_plain);
>> >>> +#endif
>> >>>   }
>> >>>   
>> >>>   void migration_test_add_precopy(MigrationTestEnv *env)
>> >>
>> >> Thanks, that's definitely better than nothing. I'll experiment with this
>> >> locally, see if I can at least run it before sending a pull request.
>> > 
>> > With your newly added --full, IIUC we can add whatever we want there.
>> > E.g. we can add --rdma and iff specified, migration-test adds the rdma test.
>> > 
>> > Or.. skip the test when the rdma link isn't available.
>> > 
>> > If we could separate the script into a file, it'll be better.  We could
>> > create scripts/migration dir and put all migration scripts over there,
>> 
>> We have any other existing script? I didn't find it in current QEMU tree.
>
> We have a few that I'm aware of:
>
>   - analyze-migration.py
>   - vmstate-static-checker.py
>   - userfaultfd-wrlat.py
>

If it cannot be reached from there for some reason, we could copy it to
build/tests/qtest/migration during the build. As a last resort I'm fine
with just having it directly at tests/qtest/migration like this patch
does.

>> 
>> 
>> > then
>> > in the test it tries to detect rdma link and fetch the ip only
>> 
>> It should work without root permission if we just *detect* and *fetch ip*.
>> 
>> Do you also mean we can split new-rdma-link.sh to 2 separate scripts
>> - add-rdma-link.sh # optionally, execute by user before the test (require root permission)
>> - detect-fetch-rdma.sh # execute from the migration-test
>
> Hmm indeed we still need a script to scan over all the ports..
>
> If having --rdma is a good idea, maybe we can further make it a parameter
> to --rdma?
>
>   $ migration-test --rdma $RDMA_IP
>
> Or:
>
>   $ migration-test --rdma-ip $RDMA_IP

I think --rdma only makes sense if it's going to do something
special. The optmimal scenario is that it always runs the test when it
can and sets up/tears down anything it needs.

If it needs root, I'd prefer the test informs about this and does the
work itself.

It would also be good to have the add + detect separate so we have more
flexibility, maybe we manage to enable this in CI even.

So:

./add.sh
migration-test
(runs detect.sh + runs rdma test)
(leaves stuff behind)

migration-test
(skips rdma test with message that it needs root)

sudo migration-test
(runs add.sh + detect.sh + runs rdma test)
(cleans itself up)

Does that make sense to you? I hope it's not too much work.

If you'd like to limit the usage of sudo for running the tests, then we
could indeed add the --rdma option and this would be even more
strict. The good thing of not having --rdma is that I could call add.sh
and then run the full make check afterwards, but that's not a huge deal.

> Then maybe migration-test can directly take that IP and run the tests,
> assuming the admin setup the rdma link.  Then we keep that one script.
>
> Or I assume it's still ok that the test requires root only for --rdma, then
> invoke the script directly in the test.  If so, we'd better also remove the
> rdma link after test finished, so no side effect of the test (modprobe is
> probably fine).
>
> We can wait and see how far Fabiano went with this, and also his opinion.

I haven't got the chance to try the script yet. I still need to figure
out what packages I need from the distro.