2cf7cfa1cd
This catches the situation that is described in the bug report at https://bugs.launchpad.net/qemu/+bug/865518 and goes like this: $ qemu-img create -f qcow2 huge.qcow2 $((1024*1024))T Formatting 'huge.qcow2', fmt=qcow2 size=1152921504606846976 encryption=off cluster_size=65536 lazy_refcounts=off $ qemu-io /tmp/huge.qcow2 -c "write $((1024*1024*1024*1024*1024*1024 - 1024)) 512" Segmentation fault With this patch applied the segfault will be avoided, however the case will still fail, though gracefully: $ qemu-img create -f qcow2 /tmp/huge.qcow2 $((1024*1024))T Formatting 'huge.qcow2', fmt=qcow2 size=1152921504606846976 encryption=off cluster_size=65536 lazy_refcounts=off qemu-img: The image size is too large for file format 'qcow2' Note that even long before these overflow checks kick in, you get insanely high memory usage (up to INT_MAX * sizeof(uint64_t) = 16 GB for the L1 table), so with somewhat smaller image sizes you'll probably see qemu aborting for a failed g_malloc(). If you need huge image sizes, you should increase the cluster size to the maximum of 2 MB in order to get higher limits. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Read the documentation in qemu-doc.html or on http://wiki.qemu.org - QEMU team