From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58226) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZEzPX-0003ug-7M for qemu-devel@nongnu.org; Tue, 14 Jul 2015 08:34:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZEzPT-0006q6-Sx for qemu-devel@nongnu.org; Tue, 14 Jul 2015 08:34:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48647) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZEzPT-0006py-LT for qemu-devel@nongnu.org; Tue, 14 Jul 2015 08:34:07 -0400 From: Juan Quintela In-Reply-To: <1434450415-11339-35-git-send-email-dgilbert@redhat.com> (David Alan Gilbert's message of "Tue, 16 Jun 2015 11:26:47 +0100") References: <1434450415-11339-1-git-send-email-dgilbert@redhat.com> <1434450415-11339-35-git-send-email-dgilbert@redhat.com> Date: Tue, 14 Jul 2015 14:34:03 +0200 Message-ID: <87y4iigbpg.fsf@neno.neno> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH v7 34/42] Postcopy: Use helpers to map pages during migration Reply-To: quintela@redhat.com List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert (git)" Cc: aarcange@redhat.com, yamahata@private.email.ne.jp, liang.z.li@intel.com, qemu-devel@nongnu.org, luis@cs.umu.se, amit.shah@redhat.com, pbonzini@redhat.com, david@gibson.dropbear.id.au "Dr. David Alan Gilbert (git)" wrote: > From: "Dr. David Alan Gilbert" > > In postcopy, the destination guest is running at the same time > as it's receiving pages; as we receive new pages we must put > them into the guests address space atomically to avoid a running > CPU accessing a partially written page. > > Use the helpers in postcopy-ram.c to map these pages. > > qemu_get_buffer_less_copy is used to avoid a copy out of qemu_file > in the case that postcopy is going to do a copy anyway. > > Signed-off-by: Dr. David Alan Gilbert > @@ -1742,7 +1752,6 @@ static inline void *host_from_stream_offset(QEMUFile *f, > error_report("Ack, bad migration stream!"); > return NULL; > } > - Dont' belong here O:-) > return memory_region_get_ram_ptr(block->mr) + offset; > } > > @@ -1881,6 +1890,16 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id) > int flags = 0, ret = 0; > static uint64_t seq_iter; > int len = 0; > + /* > + * System is running in postcopy mode, page inserts to host memory must be > + * atomic > + */ > + MigrationIncomingState *mis = migration_incoming_get_current(); > + bool postcopy_running = postcopy_state_get(mis) >= > + POSTCOPY_INCOMING_LISTENING; > + void *postcopy_host_page = NULL; > + bool postcopy_place_needed = false; > + bool matching_page_sizes = qemu_host_page_size == TARGET_PAGE_SIZE; > > seq_iter++; > > @@ -1896,13 +1915,57 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id) > rcu_read_lock(); > while (!ret && !(flags & RAM_SAVE_FLAG_EOS)) { > ram_addr_t addr, total_ram_bytes; > - void *host; > + void *host = 0; > + void *page_buffer = 0; > + void *postcopy_place_source = 0; NULL, NULL, NULL? BTW, do we really need postcopy_place_source? I think that just doing s/postcopy_place_source/postcopy_host_page/ would do? > uint8_t ch; > + bool all_zero = false; > > addr = qemu_get_be64(f); > flags = addr & ~TARGET_PAGE_MASK; > addr &= TARGET_PAGE_MASK; > > + if (flags & (RAM_SAVE_FLAG_COMPRESS | RAM_SAVE_FLAG_PAGE | > + RAM_SAVE_FLAG_XBZRLE)) { > + host = host_from_stream_offset(f, mis, addr, flags); > + if (!host) { > + error_report("Illegal RAM offset " RAM_ADDR_FMT, addr); > + ret = -EINVAL; > + break; > + } > + if (!postcopy_running) { > + page_buffer = host; > + } else { > + /* > + * Postcopy requires that we place whole host pages atomically. > + * To make it atomic, the data is read into a temporary page > + * that's moved into place later. > + * The migration protocol uses, possibly smaller, target-pages > + * however the source ensures it always sends all the components > + * of a host page in order. > + */ > + if (!postcopy_host_page) { > + postcopy_host_page = postcopy_get_tmp_page(mis); > + } > + page_buffer = postcopy_host_page + > + ((uintptr_t)host & ~qemu_host_page_mask); > + /* If all TP are zero then we can optimise the place */ > + if (!((uintptr_t)host & ~qemu_host_page_mask)) { I don't understand the test, the comment or both :-( How you arrive from that test that this is a page full of zeros is a mistery to me :p Head hurts, would try to convince myself that the rest of changes are ok.