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Berrange" , Leonardo Bras Soares Passos , Manish Mishra , Juan Quintela , "Dr . David Alan Gilbert" , peterx@redhat.com Subject: [PATCH RFC 05/13] migration: Disallow postcopy preempt to be used with compress Date: Mon, 29 Aug 2022 12:56:51 -0400 Message-Id: <20220829165659.96046-6-peterx@redhat.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220829165659.96046-1-peterx@redhat.com> References: <20220829165659.96046-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1661792969566100002 Content-Type: text/plain; charset="utf-8" The preempt mode requires the capability to assign channel for each of the page, while the compression logic will currently assign pages to different compress thread/local-channel so potentially they're incompatible. Signed-off-by: Peter Xu --- migration/migration.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/migration/migration.c b/migration/migration.c index bb8bbddfe4..844bca1ff6 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -1336,6 +1336,17 @@ static bool migrate_caps_check(bool *cap_list, error_setg(errp, "Postcopy preempt requires postcopy-ram"); return false; } + + /* + * Preempt mode requires urgent pages to be sent in separate + * channel, OTOH compression logic will disorder all pages into + * different compression channels, which is not compatible with the + * preempt assumptions on channel assignments. + */ + if (cap_list[MIGRATION_CAPABILITY_COMPRESS]) { + error_setg(errp, "Postcopy preempt not compatible with compres= s"); + return false; + } } =20 return true; --=20 2.32.0