From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57443) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zql63-0002oU-8m for qemu-devel@nongnu.org; Mon, 26 Oct 2015 12:58:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zql60-0000Je-3U for qemu-devel@nongnu.org; Mon, 26 Oct 2015 12:58:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56733) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zql5z-0000JY-UE for qemu-devel@nongnu.org; Mon, 26 Oct 2015 12:58:08 -0400 Date: Mon, 26 Oct 2015 16:58:01 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20151026165801.GF2500@work-vm> References: <1443515898-3594-1-git-send-email-dgilbert@redhat.com> <1443515898-3594-39-git-send-email-dgilbert@redhat.com> <87r3koa311.fsf@neno.neno> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87r3koa311.fsf@neno.neno> Subject: Re: [Qemu-devel] [PATCH v8 38/54] Page request: Add MIG_RP_MSG_REQ_PAGES reverse command List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Juan Quintela Cc: aarcange@redhat.com, liang.z.li@intel.com, qemu-devel@nongnu.org, luis@cs.umu.se, bharata@linux.vnet.ibm.com, amit.shah@redhat.com, pbonzini@redhat.com * Juan Quintela (quintela@redhat.com) wrote: > "Dr. David Alan Gilbert (git)" wrote: > > From: "Dr. David Alan Gilbert" > > > > Add MIG_RP_MSG_REQ_PAGES command on Return path for the postcopy > > destination to request a page from the source. > > > > Two versions exist: > > MIG_RP_MSG_REQ_PAGES_ID that includes a RAMBlock name and start/len > > MIG_RP_MSG_REQ_PAGES that just has start/len for use with the same > > RAMBlock as a previous MIG_RP_MSG_REQ_PAGES_ID > > > > Signed-off-by: Dr. David Alan Gilbert > > > Reviewed-by: Juan Quintela > > > > diff --git a/migration/migration.c b/migration/migration.c > > index 4f8ef6f..e994164 100644 > > --- a/migration/migration.c > > +++ b/migration/migration.c > > @@ -251,6 +251,35 @@ static void deferred_incoming_migration(Error **errp) > > deferred_incoming = true; > > } > > > > +/* Request a range of pages from the source VM at the given > > + * start address. > > + * rbname: Name of the RAMBlock to request the page in, if NULL it's the same > > + * as the last request (a name must have been given previously) > > + * Start: Address offset within the RB > > + * Len: Length in bytes required - must be a multiple of pagesize > > + */ > > +void migrate_send_rp_req_pages(MigrationIncomingState *mis, const char *rbname, > > + ram_addr_t start, size_t len) > > +{ > > + uint8_t bufc[12 + 1 + 255]; /* start (8), len (4), rbname upto 256 */ > > + size_t msglen = 12; /* start + len */ > > + > > + *(uint64_t *)bufc = cpu_to_be64((uint64_t)start); > > + *(uint32_t *)(bufc + 8) = cpu_to_be32((uint32_t)len); > > struct foo { > uint64_t start; > uint32_t len; > char msg[]; > } > > As we are supposed to have the same qemu on both sides, this should > work, no? In principal I think it should work between opposite endian hosts; if they are capable of running the same endian guest (untested); similarly there's no requirement for the two qemu's to be built with the same compiler, or I think host word size. Using structs on a wire always makes me start worrying what the compiler would do to the layout; I'd assume it would at least need a 'packed' to be sure a particularly entertaining compiler doesn't do something odd. > Reviewed by anyways, because I am not sure that proposed solution is > (even) better than current code. Dave > > Later, Juan. -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK