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From 34dc905251ca0f00d92e8419adc63580c6266394 Mon Sep 17 00:00:00 2001
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Message-Id: <34dc905251ca0f00d92e8419adc63580c6266394@dist-git>
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From: Jiri Denemark <jdenemar@redhat.com>
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Date: Wed, 22 Jun 2022 16:37:31 +0200
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Subject: [PATCH] qemu_migration: Implement VIR_MIGRATE_ZEROCOPY flag
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Resolves: https://gitlab.com/libvirt/libvirt/-/issues/306
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Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
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Reviewed-by: Ján Tomko <jtomko@redhat.com>
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(cherry picked from commit d375993ab314a41bca7ef6c846e07afc18c37774)
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https://bugzilla.redhat.com/show_bug.cgi?id=2117272
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Conflicts:
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	src/qemu/qemu_migration.c
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	src/qemu/qemu_migration.h
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            - post-copy recovery not bacported
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Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
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---
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 src/qemu/qemu_migration.c        | 21 +++++++++++++++++++++
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 src/qemu/qemu_migration.h        |  1 +
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 src/qemu/qemu_migration_params.c |  6 ++++++
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 src/qemu/qemu_migration_params.h |  1 +
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 4 files changed, 29 insertions(+)
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diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
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index 01102c4300..11f87296d6 100644
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--- a/src/qemu/qemu_migration.c
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+++ b/src/qemu/qemu_migration.c
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@@ -2366,6 +2366,12 @@ qemuMigrationSrcBeginPhase(virQEMUDriver *driver,
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         return NULL;
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     }
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+    if (flags & VIR_MIGRATE_ZEROCOPY && !(flags & VIR_MIGRATE_PARALLEL)) {
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+        virReportError(VIR_ERR_OPERATION_INVALID, "%s",
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+                       _("zero-copy is only available for parallel migration"));
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+        return NULL;
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+    }
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+
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     if (flags & (VIR_MIGRATE_NON_SHARED_DISK | VIR_MIGRATE_NON_SHARED_INC)) {
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         if (flags & VIR_MIGRATE_NON_SHARED_SYNCHRONOUS_WRITES &&
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             !virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_BLOCKDEV)) {
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@@ -4137,6 +4143,21 @@ qemuMigrationSrcRun(virQEMUDriver *driver,
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                                  migParams) < 0)
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         goto error;
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+    if (flags & VIR_MIGRATE_ZEROCOPY) {
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+        /* Zero-copy requires pages in transfer to be locked in host memory.
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+         * Unfortunately, we have no reliable way of computing how many pages
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+         * will need to be locked at the same time. Thus we set the limit to
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+         * the whole guest memory and reset it back once migration is done. */
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+        unsigned long long limit;
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+
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+        if (virMemoryLimitIsSet(vm->def->mem.hard_limit))
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+            limit = vm->def->mem.hard_limit;
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+        else
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+            limit = virDomainDefGetMemoryTotal(vm->def);
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+
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+        if (qemuDomainSetMaxMemLock(vm, limit << 10, &priv->preMigrationMemlock) < 0)
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+            goto error;
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+    }
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     if (storageMigration) {
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         if (mig->nbd) {
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diff --git a/src/qemu/qemu_migration.h b/src/qemu/qemu_migration.h
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index b233358a51..6f737f7b4c 100644
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--- a/src/qemu/qemu_migration.h
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+++ b/src/qemu/qemu_migration.h
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@@ -60,6 +60,7 @@
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      VIR_MIGRATE_TLS | \
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      VIR_MIGRATE_PARALLEL | \
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      VIR_MIGRATE_NON_SHARED_SYNCHRONOUS_WRITES | \
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+     VIR_MIGRATE_ZEROCOPY | \
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      0)
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 /* All supported migration parameters and their types. */
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diff --git a/src/qemu/qemu_migration_params.c b/src/qemu/qemu_migration_params.c
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index 7b225fdf4b..c985583861 100644
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--- a/src/qemu/qemu_migration_params.c
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+++ b/src/qemu/qemu_migration_params.c
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@@ -96,6 +96,7 @@ VIR_ENUM_IMPL(qemuMigrationCapability,
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               "multifd",
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               "dirty-bitmaps",
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               "return-path",
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+              "zero-copy-send",
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 );
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@@ -177,6 +178,11 @@ static const qemuMigrationParamsFlagMapItem qemuMigrationParamsFlagMap[] = {
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      VIR_MIGRATE_TUNNELLED,
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      QEMU_MIGRATION_CAP_RETURN_PATH,
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      QEMU_MIGRATION_SOURCE | QEMU_MIGRATION_DESTINATION},
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+
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+    {QEMU_MIGRATION_FLAG_REQUIRED,
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+     VIR_MIGRATE_ZEROCOPY,
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+     QEMU_MIGRATION_CAP_ZERO_COPY_SEND,
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+     QEMU_MIGRATION_SOURCE},
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 };
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 /* Translation from VIR_MIGRATE_PARAM_* typed parameters to
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diff --git a/src/qemu/qemu_migration_params.h b/src/qemu/qemu_migration_params.h
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index b4de8dda7b..caa5e47f0f 100644
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--- a/src/qemu/qemu_migration_params.h
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+++ b/src/qemu/qemu_migration_params.h
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@@ -41,6 +41,7 @@ typedef enum {
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     QEMU_MIGRATION_CAP_MULTIFD,
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     QEMU_MIGRATION_CAP_BLOCK_DIRTY_BITMAPS,
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     QEMU_MIGRATION_CAP_RETURN_PATH,
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+    QEMU_MIGRATION_CAP_ZERO_COPY_SEND,
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     QEMU_MIGRATION_CAP_LAST
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 } qemuMigrationCapability;
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-- 
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2.35.1
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