From 0753565af588dfa78b3529e359b1590e15fcbdb3 Mon Sep 17 00:00:00 2001

From: Leonardo Bras <leobras@redhat.com>

Date: Tue, 19 Jul 2022 09:23:45 -0300

Subject: [PATCH 04/11] migration: Avoid false-positive on non-supported

 scenarios for zero-copy-send

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RH-Author: Leonardo Brás <leobras@redhat.com>

RH-MergeRequest: 111: zero-copy-send fixes & improvements

RH-Commit: [4/6] f5c7ed6710d92668acb81d0118a71fab0b4e3d43 (LeoBras/centos-qemu-kvm)

RH-Bugzilla: 2107466

RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

RH-Acked-by: Thomas Huth <thuth@redhat.com>

RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Migration with zero-copy-send currently has it's limitations, as it can't

be used with TLS nor any kind of compression. In such scenarios, it should

output errors during parameter / capability setting.

But currently there are some ways of setting this not-supported scenarios

without printing the error message:

!) For 'compression' capability, it works by enabling it together with

zero-copy-send. This happens because the validity test for zero-copy uses

the helper unction migrate_use_compression(), which check for compression

presence in s->enabled_capabilities[MIGRATION_CAPABILITY_COMPRESS].

The point here is: the validity test happens before the capability gets

enabled. If all of them get enabled together, this test will not return

error.

In order to fix that, replace migrate_use_compression() by directly testing

the cap_list parameter migrate_caps_check().

2) For features enabled by parameters such as TLS & 'multifd_compression',

there was also a possibility of setting non-supported scenarios: setting

zero-copy-send first, then setting the unsupported parameter.

In order to fix that, also add a check for parameters conflicting with

zero-copy-send on migrate_params_check().

3) XBZRLE is also a compression capability, so it makes sense to also add

it to the list of capabilities which are not supported with zero-copy-send.

Fixes: 1abaec9a1b2c ("migration: Change zero_copy_send from migration parameter to migration capability")

Signed-off-by: Leonardo Bras <leobras@redhat.com>

Message-Id: <20220719122345.253713-1-leobras@redhat.com>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

(cherry picked from commit 90eb69e4f1a16b388d0483543bf6bfc69a9966e4)

Signed-off-by: Leonardo Bras <leobras@redhat.com>

---

 migration/migration.c | 15 ++++++++++++++-

 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/migration/migration.c b/migration/migration.c

index 3a3a7a4a50..343629d59c 100644

--- a/migration/migration.c

+++ b/migration/migration.c

@@ -1265,7 +1265,9 @@ static bool migrate_caps_check(bool *cap_list,

 #ifdef CONFIG_LINUX

     if (cap_list[MIGRATION_CAPABILITY_ZERO_COPY_SEND] &&

         (!cap_list[MIGRATION_CAPABILITY_MULTIFD] ||

-         migrate_use_compression() ||

+         cap_list[MIGRATION_CAPABILITY_COMPRESS] ||

+         cap_list[MIGRATION_CAPABILITY_XBZRLE] ||

+         migrate_multifd_compression() ||

          migrate_use_tls())) {

         error_setg(errp,

                    "Zero copy only available for non-compressed non-TLS multifd migration");

@@ -1502,6 +1504,17 @@ static bool migrate_params_check(MigrationParameters *params, Error **errp)

         error_prepend(errp, "Invalid mapping given for block-bitmap-mapping: ");

         return false;

     }

+

+#ifdef CONFIG_LINUX

+    if (migrate_use_zero_copy_send() &&

+        ((params->has_multifd_compression && params->multifd_compression) ||

+         (params->has_tls_creds && params->tls_creds && *params->tls_creds))) {

+        error_setg(errp,

+                   "Zero copy only available for non-compressed non-TLS multifd migration");

+        return false;

+    }

+#endif

+

     return true;

 }

-- 

2.31.1