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Wed, 6 Nov 2019 20:08:30 +0000 (UTC) Date: Wed, 6 Nov 2019 20:08:28 +0000 From: "Dr. David Alan Gilbert" To: Wei Yang Subject: Re: [PATCH 5/6] migration/postcopy: enable random order target page arrival Message-ID: <20191106200828.GL2802@work-vm> References: <20191018004850.9888-1-richardw.yang@linux.intel.com> <20191018004850.9888-6-richardw.yang@linux.intel.com> MIME-Version: 1.0 In-Reply-To: <20191018004850.9888-6-richardw.yang@linux.intel.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-MC-Unique: p8iA-lzXPdGaE3kyi9kqRg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.61 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: qemu-devel@nongnu.org, quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Wei Yang (richardw.yang@linux.intel.com) wrote: > After using number of target page received to track one host page, we > could have the capability to handle random order target page arrival in > one host page. >=20 > This is a preparation for enabling compress during postcopy. >=20 > Signed-off-by: Wei Yang > --- > migration/ram.c | 16 +++------------- > 1 file changed, 3 insertions(+), 13 deletions(-) >=20 > diff --git a/migration/ram.c b/migration/ram.c > index b5759793a9..da0596411c 100644 > --- a/migration/ram.c > +++ b/migration/ram.c > @@ -4015,7 +4015,6 @@ static int ram_load_postcopy(QEMUFile *f) > MigrationIncomingState *mis =3D migration_incoming_get_current(); > /* Temporary page that is later 'placed' */ > void *postcopy_host_page =3D mis->postcopy_tmp_page; > - void *last_host =3D NULL; > bool all_zero =3D false; > int target_pages =3D 0; > =20 > @@ -4062,24 +4061,15 @@ static int ram_load_postcopy(QEMUFile *f) > * that's moved into place later. > * The migration protocol uses, possibly smaller, target-pa= ges > * however the source ensures it always sends all the compon= ents > - * of a host page in order. > + * of a host page in one chunk. > */ > page_buffer =3D postcopy_host_page + > ((uintptr_t)host & (block->page_size - 1)); > /* If all TP are zero then we can optimise the place */ > if (target_pages =3D=3D 1) { > all_zero =3D true; > - } else { > - /* not the 1st TP within the HP */ > - if (host !=3D (last_host + TARGET_PAGE_SIZE)) { > - error_report("Non-sequential target page %p/%p", > - host, last_host); > - ret =3D -EINVAL; > - break; > - } I think this is losing more protection than needed. I think you can still protect against a page from a different host-page arriving until we've placed the current host-page. So something like: if (((uintptr_t)host & ~(block->page_size - 1)) !=3D last_host) and then set last_host to the start of the host page. Then you'll check if that flush is really working. Dave > } > =20 > - > /* > * If it's the last part of a host page then we place the ho= st > * page > @@ -4090,7 +4080,6 @@ static int ram_load_postcopy(QEMUFile *f) > } > place_source =3D postcopy_host_page; > } > - last_host =3D host; > =20 > switch (flags & ~RAM_SAVE_FLAG_CONTINUE) { > case RAM_SAVE_FLAG_ZERO: > @@ -4143,7 +4132,8 @@ static int ram_load_postcopy(QEMUFile *f) > =20 > if (!ret && place_needed) { > /* This gets called at the last target page in the host page= */ > - void *place_dest =3D host + TARGET_PAGE_SIZE - block->page_s= ize; > + void *place_dest =3D (void *)QEMU_ALIGN_DOWN((unsigned long)= host, > + block->page_size)= ; > =20 > if (all_zero) { > ret =3D postcopy_place_page_zero(mis, place_dest, > --=20 > 2.17.1 >=20 -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK