From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41209) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d3Roi-0000I7-Jz for qemu-devel@nongnu.org; Wed, 26 Apr 2017 14:37:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d3Rog-0006Y5-FE for qemu-devel@nongnu.org; Wed, 26 Apr 2017 14:37:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41064) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1d3Rog-0006Xr-5Z for qemu-devel@nongnu.org; Wed, 26 Apr 2017 14:37:30 -0400 From: "Dr. David Alan Gilbert (git)" Date: Wed, 26 Apr 2017 19:37:20 +0100 Message-Id: <20170426183721.7482-2-dgilbert@redhat.com> In-Reply-To: <20170426183721.7482-1-dgilbert@redhat.com> References: <20170426183721.7482-1-dgilbert@redhat.com> Subject: [Qemu-devel] [PATCH 1/2] Postcopy: Force allocation of all-zero precopy pages List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, borntraeger@de.ibm.com, quintela@redhat.com, lvivier@redhat.com, peterx@redhat.com From: "Dr. David Alan Gilbert" When an all-zero page is received during the precopy phase of a postcopy-enabled migration we must force allocation otherwise accesses to the page will still get blocked by userfault. Symptom: a) If the page is accessed by a device during device-load then we get a deadlock as the source finishes sending all its pages but the destination device-load is still paused and so doesn't clean up. b) If the page is accessed later, then the thread will stay paused until the end of migration rather than carrying on running, until we release userfault at the end. Signed-off-by: Dr. David Alan Gilbert Reported-by: Christian Borntraeger --- include/migration/migration.h | 3 ++- migration/ram.c | 12 ++++++++---- migration/rdma.c | 2 +- 3 files changed, 11 insertions(+), 6 deletions(-) diff --git a/include/migration/migration.h b/include/migration/migration.h index ba1a16cbc1..b47904033c 100644 --- a/include/migration/migration.h +++ b/include/migration/migration.h @@ -265,7 +265,8 @@ uint64_t xbzrle_mig_pages_overflow(void); uint64_t xbzrle_mig_pages_cache_miss(void); double xbzrle_mig_cache_miss_rate(void); -void ram_handle_compressed(void *host, uint8_t ch, uint64_t size); +void ram_handle_compressed(void *host, uint8_t ch, uint64_t size, + bool always_write); void ram_debug_dump_bitmap(unsigned long *todump, bool expected); /* For outgoing discard bitmap */ int ram_postcopy_send_discard_bitmap(MigrationState *ms); diff --git a/migration/ram.c b/migration/ram.c index f48664ec62..b4ed41c725 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -2274,10 +2274,12 @@ static inline void *host_from_ram_block_offset(RAMBlock *block, * @host: host address for the zero page * @ch: what the page is filled from. We only support zero * @size: size of the zero page + * @always_write: Always perform the memset even if it's zero */ -void ram_handle_compressed(void *host, uint8_t ch, uint64_t size) +void ram_handle_compressed(void *host, uint8_t ch, uint64_t size, + bool always_write) { - if (ch != 0 || !is_zero_range(host, size)) { + if (ch != 0 || always_write || !is_zero_range(host, size)) { memset(host, ch, size); } } @@ -2514,7 +2516,8 @@ static int ram_load_postcopy(QEMUFile *f) switch (flags & ~RAM_SAVE_FLAG_CONTINUE) { case RAM_SAVE_FLAG_COMPRESS: ch = qemu_get_byte(f); - memset(page_buffer, ch, TARGET_PAGE_SIZE); + ram_handle_compressed(page_buffer, ch, TARGET_PAGE_SIZE, + true); if (ch) { all_zero = false; } @@ -2664,7 +2667,8 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id) case RAM_SAVE_FLAG_COMPRESS: ch = qemu_get_byte(f); - ram_handle_compressed(host, ch, TARGET_PAGE_SIZE); + ram_handle_compressed(host, ch, TARGET_PAGE_SIZE, + postcopy_advised); break; case RAM_SAVE_FLAG_PAGE: diff --git a/migration/rdma.c b/migration/rdma.c index fe0a4b5a83..07a9bd75d8 100644 --- a/migration/rdma.c +++ b/migration/rdma.c @@ -3164,7 +3164,7 @@ static int qemu_rdma_registration_handle(QEMUFile *f, void *opaque) host_addr = block->local_host_addr + (comp->offset - block->offset); - ram_handle_compressed(host_addr, comp->value, comp->length); + ram_handle_compressed(host_addr, comp->value, comp->length, false); break; case RDMA_CONTROL_REGISTER_FINISHED: -- 2.12.2