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Thu, 20 Feb 2020 15:16:17 +0000 (UTC) Received: from [10.36.118.29] (unknown [10.36.118.29]) by smtp.corp.redhat.com (Postfix) with ESMTP id E584186E07; Thu, 20 Feb 2020 15:16:04 +0000 (UTC) Subject: Re: [PATCH v1 05/13] migrate/ram: Handle RAM block resizes during precopy To: qemu-devel@nongnu.org References: <20200219161725.115218-1-david@redhat.com> <20200219161725.115218-6-david@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: <3c3d4d50-a30d-b4e9-6256-4656f4e78cf6@redhat.com> Date: Thu, 20 Feb 2020 16:16:02 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200219161725.115218-6-david@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-MC-Unique: U1c4k70bPE-KcPvEJa4-EQ-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Eduardo Habkost , Juan Quintela , "Michael S. Tsirkin" , Richard Henderson , "Dr . David Alan Gilbert" , Peter Xu , Shannon Zhao , Igor Mammedov , Paolo Bonzini , =?UTF-8?Q?Alex_Benn=c3=a9e?= , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 19.02.20 17:17, David Hildenbrand wrote: > Resizing while migrating is dangerous and does not work as expected. > The whole migration code works on the usable_length of ram blocks and doe= s > not expect this to change at random points in time. >=20 > In the case of precopy, the ram block size must not change on the source, > after syncing the RAM block list in ram_save_setup(), so as long as the > guest is still running on the source. >=20 > Resizing can be trigger *after* (but not during) a reset in > ACPI code by the guest > - hw/arm/virt-acpi-build.c:acpi_ram_update() > - hw/i386/acpi-build.c:acpi_ram_update() >=20 > Use the ram block notifier to get notified about resizes. Let's simply > cancel migration and indicate the reason. We'll continue running on the > source. No harm done. >=20 > Update the documentation. Postcopy will be handled separately. >=20 > Cc: "Dr. David Alan Gilbert" > Cc: Juan Quintela > Cc: Eduardo Habkost > Cc: Paolo Bonzini > Cc: Igor Mammedov > Cc: "Michael S. Tsirkin" > Cc: Richard Henderson > Cc: Shannon Zhao > Cc: Alex Benn=C3=A9e > Cc: Peter Xu > Signed-off-by: David Hildenbrand > --- > exec.c | 5 +++-- > include/exec/memory.h | 10 ++++++---- > migration/migration.c | 9 +++++++-- > migration/migration.h | 1 + > migration/ram.c | 41 +++++++++++++++++++++++++++++++++++++++++ > 5 files changed, 58 insertions(+), 8 deletions(-) >=20 > diff --git a/exec.c b/exec.c > index b75250e773..8b015821d6 100644 > --- a/exec.c > +++ b/exec.c > @@ -2120,8 +2120,9 @@ static int memory_try_enable_merging(void *addr, si= ze_t len) > return qemu_madvise(addr, len, QEMU_MADV_MERGEABLE); > } > =20 > -/* Only legal before guest might have detected the memory size: e.g. on > - * incoming migration, or right after reset. > +/* > + * Resizing RAM while migrating can result in the migration being cancel= ed. > + * Care has to be taken if the guest might have already detected the mem= ory. > * > * As memory core doesn't know how is memory accessed, it is up to > * resize callback to update device state and/or add assertions to detec= t > diff --git a/include/exec/memory.h b/include/exec/memory.h > index e85b7de99a..de111347e8 100644 > --- a/include/exec/memory.h > +++ b/include/exec/memory.h > @@ -113,7 +113,7 @@ typedef struct IOMMUNotifier IOMMUNotifier; > #define RAM_SHARED (1 << 1) > =20 > /* Only a portion of RAM (used_length) is actually used, and migrated. > - * This used_length size can change across reboots. > + * Resizing RAM while migrating can result in the migration being cancel= ed. > */ > #define RAM_RESIZEABLE (1 << 2) > =20 > @@ -843,7 +843,9 @@ void memory_region_init_ram_shared_nomigrate(MemoryRe= gion *mr, > * RAM. Accesses into the region wi= ll > * modify memory directly. Only an = initial > * portion of this RAM is actually u= sed. > - * The used size can change across r= eboots. > + * Changing the size while migrating > + * can result in the migration being > + * canceled. > * > * @mr: the #MemoryRegion to be initialized. > * @owner: the object that tracks the region's reference count > @@ -1464,8 +1466,8 @@ void *memory_region_get_ram_ptr(MemoryRegion *mr); > =20 > /* memory_region_ram_resize: Resize a RAM region. > * > - * Only legal before guest might have detected the memory size: e.g. on > - * incoming migration, or right after reset. > + * Resizing RAM while migrating can result in the migration being cancel= ed. > + * Care has to be taken if the guest might have already detected the mem= ory. > * > * @mr: a memory region created with @memory_region_init_resizeable_ram. > * @newsize: the new size the region > diff --git a/migration/migration.c b/migration/migration.c > index 8fb68795dc..ac9751dbe5 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -175,13 +175,18 @@ void migration_object_init(void) > } > } > =20 > +void migration_cancel(void) > +{ > + migrate_fd_cancel(current_migration); > +} > + > void migration_shutdown(void) > { > /* > * Cancel the current migration - that will (eventually) > * stop the migration using this structure > */ > - migrate_fd_cancel(current_migration); > + migration_cancel(); > object_unref(OBJECT(current_migration)); > } > =20 > @@ -2019,7 +2024,7 @@ void qmp_migrate(const char *uri, bool has_blk, boo= l blk, > =20 > void qmp_migrate_cancel(Error **errp) > { > - migrate_fd_cancel(migrate_get_current()); > + migration_cancel(); > } > =20 > void qmp_migrate_continue(MigrationStatus state, Error **errp) > diff --git a/migration/migration.h b/migration/migration.h > index 8473ddfc88..79fd74afa5 100644 > --- a/migration/migration.h > +++ b/migration/migration.h > @@ -343,5 +343,6 @@ int foreach_not_ignored_block(RAMBlockIterFunc func, = void *opaque); > void migration_make_urgent_request(void); > void migration_consume_urgent_request(void); > bool migration_rate_limit(void); > +void migration_cancel(void); > =20 > #endif > diff --git a/migration/ram.c b/migration/ram.c > index ed23ed1c7c..57f32011a3 100644 > --- a/migration/ram.c > +++ b/migration/ram.c > @@ -52,6 +52,7 @@ > #include "migration/colo.h" > #include "block.h" > #include "sysemu/sysemu.h" > +#include "sysemu/runstate.h" > #include "savevm.h" > #include "qemu/iov.h" > #include "multifd.h" > @@ -3710,8 +3711,48 @@ static SaveVMHandlers savevm_ram_handlers =3D { > .resume_prepare =3D ram_resume_prepare, > }; > =20 > +static void ram_mig_ram_block_resized(RAMBlockNotifier *n, void *host, > + size_t old_size, size_t new_size) > +{ > + ram_addr_t offset; > + Error *err =3D NULL; > + RAMBlock *rb =3D qemu_ram_block_from_host(host, false, &offset); > + > + if (ramblock_is_ignored(rb)) { > + return; > + } > + > + /* > + * Some resizes are triggered on the migration target by precopy cod= e, > + * when synchronizing RAM block sizes. In these cases, the VM is not > + * running and migration is not idle. We have to ignore these resize= s, > + * as we only care about resizes during precopy on the migration sou= rce. > + * This handler is always registered, so ignore when migration is id= le. > + */ > + if (migration_is_idle() || !runstate_is_running() || > + postcopy_is_running()) { > + return; > + } > + > + /* > + * Precopy code cannot deal with the size of ram blocks changing at > + * random points in time. We're still running on the source, abort > + * the migration and continue running here. Make sure to wait until > + * migration was canceled. > + */ > + error_setg(&err, "RAM block '%s' resized during precopy.", rb->idstr= ); > + migrate_set_error(migrate_get_current(), err); > + error_free(err); > + migration_cancel(); > +} > + > +static RAMBlockNotifier ram_mig_ram_notifier =3D { > + .ram_block_resized =3D ram_mig_ram_block_resized, > +}; > + > void ram_mig_init(void) > { > qemu_mutex_init(&XBZRLE.lock); > register_savevm_live("ram", 0, 4, &savevm_ram_handlers, &ram_state); > + ram_block_notifier_add(&ram_mig_ram_notifier); > } >=20 So, this seems to work very reliably when triggering a resize of a RAM block during system reset (using my virtio-mem prototype): (qemu) info migrate globals: store-global-state: on only-migratable: off send-configuration: on send-section-footer: on decompress-error-check: on clear-bitmap-shift: 18 Migration status: cancelled total time: 0 milliseconds And from QEMU qemu-system-x86_64: RAM block '0000:00:03.0/mem1' resized during precopy. --=20 Thanks, David / dhildenb