On 5 November 2013 09:00, Paolo Bonzini <pbonz...@redhat.com> wrote: > Il 05/11/2013 01:36, Peter Maydell ha scritto: >> On 27 September 2013 17:49, Amos Kong <ak...@redhat.com> wrote: >>> # qemu -drive file=/disk0,if=none,id=v0,format=qcow2 \ >>> -device virtio-blk-pci,drive=v0,id=v00,multifunction=on,addr=0x04.0 >>> .... >>> >>> Launching guest with more than 32 virtio-blk disks, >>> qemu will crash, because there are too many BARs. >>> >>> This patch brings the limit of non-tcg up by a factor >>> of 8 (32767 / 4096), i.e. 32*8 = 256.
>> This looks really weird. Why should the memory subsystem >> care whether we're using TCG or KVM or Xen? > > Because only TCG stores the section number in the low bits of the iotlb > entry. This is exactly what is explained in the comments. So presumably we still crash if there are more than 32 virtio-blk disks on TCG (and indeed if more than 256 on KVM)? That doesn't seem very satisfactory... -- PMM
