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Thu, 7 Nov 2019 09:14:07 +0000 (UTC) Date: Thu, 7 Nov 2019 09:14:05 +0000 From: "Dr. David Alan Gilbert" To: Wei Yang Subject: Re: [PATCH 5/6] migration/postcopy: enable random order target page arrival Message-ID: <20191107091405.GA2816@work-vm> References: <20191018004850.9888-1-richardw.yang@linux.intel.com> <20191018004850.9888-6-richardw.yang@linux.intel.com> <20191106200828.GL2802@work-vm> <20191107060010.GA13394@richard> MIME-Version: 1.0 In-Reply-To: <20191107060010.GA13394@richard> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-MC-Unique: xFAcQc8aPF-QJqajojE4kg-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: 205.139.110.120 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: > On Wed, Nov 06, 2019 at 08:08:28PM +0000, Dr. David Alan Gilbert wrote: > >* 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 i= n > >> 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= -pages > >> * however the source ensures it always sends all the com= ponents > >> - * 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) > > >=20 > OK, looks reasonable. >=20 > >and then set last_host to the start of the host page. > > >=20 > I think it is not necessary to update the last_host on each target page. = We > can just set it at the first target page. Yes, that would be fine. Dave > >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= host > >> * 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 p= age */ > >> - void *place_dest =3D host + TARGET_PAGE_SIZE - block->pag= e_size; > >> + void *place_dest =3D (void *)QEMU_ALIGN_DOWN((unsigned lo= ng)host, > >> + block->page_si= ze); > >> =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 >=20 > --=20 > Wei Yang > Help you, Help me -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK