From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58865) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZgwHi-0004nI-HL for qemu-devel@nongnu.org; Tue, 29 Sep 2015 10:53:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZgwHe-0005RV-J9 for qemu-devel@nongnu.org; Tue, 29 Sep 2015 10:53:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37142) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZgwHe-0005RH-Da for qemu-devel@nongnu.org; Tue, 29 Sep 2015 10:53:34 -0400 From: Igor Mammedov Date: Tue, 29 Sep 2015 16:53:27 +0200 Message-Id: <1443538409-145558-1-git-send-email-imammedo@redhat.com> Subject: [Qemu-devel] [PATCH v3 0/2] pc: memhp: enforce gaps between DIMMs List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: pbonzini@redhat.com, bharata@linux.vnet.ibm.com, ehabkost@redhat.com, david@gibson.dropbear.id.au, mst@redhat.com v3: - use pc_machine_class_init() for default. (Eduardo) - make 'gap' boolean and just add 1 byte gap when calculating new_addr for DIMM. v2: make inter_dimm_gap a boolean and inster gap in 1 byte instead of 2Mb, due to alignment that gap would be extended up to natural backend alignment value. it's a simplier way suggested by Michael S. Tsirkin to workaround virtio bug reported earlier: http://lists.nongnu.org/archive/html/qemu-devel/2015-08/msg00522.html where virtio can't handle buffer that crosses border between 2 DIMM's (i.e. 2 MemoryRegions). idea is to leave gaps between DIMMs, making their GPAs non contiguous, which effectively forces kmalloc to not use DIMM if buffer doesn't fit inside of it. Simpler reproducer: qemu-system-x86_64 -enable-kvm -m 256,slots=250,maxmem=32G -drive if=virtio,file=/dev/slow/rhel72 \ `for i in $(seq 0 58); do echo -n "-object memory-backend-ram,id=m$i,size=10M -device pc-dimm,id=dimm$i,memdev=m$i "; done` \ -nodefaults -snapshot -serial stdio -nographic -M pc-i440fx-2.4 if guest manages to boot just login and do: dd if=/dev/vda of=/dev/null bs=128M it will crash QEMU in 99% cases with following message: qemu-system-x86_64: virtio: error trying to map MMIO memory Tested vs master and mst/PCI trees. Igor Mammedov (2): memhp: extend address auto assignment to support gaps pc: memhp: force gaps between DIMM's GPA hw/i386/pc.c | 5 ++++- hw/i386/pc_piix.c | 1 + hw/i386/pc_q35.c | 1 + hw/mem/pc-dimm.c | 15 +++++++++------ hw/ppc/spapr.c | 2 +- include/hw/i386/pc.h | 1 + include/hw/mem/pc-dimm.h | 7 ++++--- 7 files changed, 21 insertions(+), 11 deletions(-) -- 1.8.3.1