mirror of https://github.com/xemu-project/xemu.git
3009edff81
QEMU currently truncates the mmap_offset field when sending
VHOST_USER_ADD_MEM_REG and VHOST_USER_REM_MEM_REG messages. The struct
layout looks like this:
typedef struct VhostUserMemoryRegion {
uint64_t guest_phys_addr;
uint64_t memory_size;
uint64_t userspace_addr;
uint64_t mmap_offset;
} VhostUserMemoryRegion;
typedef struct VhostUserMemRegMsg {
uint32_t padding;
/* WARNING: there is a 32-bit hole here! */
VhostUserMemoryRegion region;
} VhostUserMemRegMsg;
The payload size is calculated as follows when sending the message in
hw/virtio/vhost-user.c:
msg->hdr.size = sizeof(msg->payload.mem_reg.padding) +
sizeof(VhostUserMemoryRegion);
This calculation produces an incorrect result of only 36 bytes.
sizeof(VhostUserMemRegMsg) is actually 40 bytes.
The consequence of this is that the final field, mmap_offset, is
truncated. This breaks x86_64 TCG guests on s390 hosts. Other guest/host
combinations may get lucky if either of the following holds:
1. The guest memory layout does not need mmap_offset != 0.
2. The host is little-endian and mmap_offset <= 0xffffffff so the
truncation has no effect.
Fix this by extending the existing 32-bit padding field to 64-bit. Now
the padding reflects the actual compiler padding. This can be verified
using pahole(1).
Also document the layout properly in the vhost-user specification. The
vhost-user spec did not document the exact layout. It would be
impossible to implement the spec without looking at the QEMU source
code.
Existing vhost-user frontends and device backends continue to work after
this fix has been applied. The only change in the wire protocol is that
QEMU now sets hdr.size to 40 instead of 36. If a vhost-user
implementation has a hardcoded size check for 36 bytes, then it will
fail with new QEMUs. Both QEMU and DPDK/SPDK don't check the exact
payload size, so they continue to work.
Fixes:
|
||
|---|---|---|
| .github | ||
| .gitlab-ci.d | ||
| accel | ||
| audio | ||
| authz | ||
| backends | ||
| block | ||
| bsd-user | ||
| capstone@f8b1b83301 | ||
| chardev | ||
| contrib | ||
| crypto | ||
| default-configs | ||
| disas | ||
| docs | ||
| dtc@85e5d83984 | ||
| dump | ||
| fpu | ||
| fsdev | ||
| gdb-xml | ||
| hw | ||
| include | ||
| io | ||
| libdecnumber | ||
| linux-headers | ||
| linux-user | ||
| meson@776acd2a80 | ||
| migration | ||
| monitor | ||
| nbd | ||
| net | ||
| pc-bios | ||
| plugins | ||
| po | ||
| python | ||
| qapi | ||
| qga | ||
| qobject | ||
| qom | ||
| replay | ||
| roms | ||
| scripts | ||
| scsi | ||
| slirp@ce94eba204 | ||
| softmmu | ||
| storage-daemon | ||
| stubs | ||
| target | ||
| tcg | ||
| tests | ||
| tools | ||
| trace | ||
| ui | ||
| util | ||
| .cirrus.yml | ||
| .dir-locals.el | ||
| .editorconfig | ||
| .exrc | ||
| .gdbinit | ||
| .gitignore | ||
| .gitlab-ci.yml | ||
| .gitmodules | ||
| .gitpublish | ||
| .mailmap | ||
| .patchew.yml | ||
| .readthedocs.yml | ||
| .shippable.yml | ||
| .travis.yml | ||
| CODING_STYLE.rst | ||
| COPYING | ||
| COPYING.LIB | ||
| Kconfig | ||
| Kconfig.host | ||
| LICENSE | ||
| MAINTAINERS | ||
| Makefile | ||
| README.rst | ||
| VERSION | ||
| block.c | ||
| blockdev-nbd.c | ||
| blockdev.c | ||
| blockjob.c | ||
| configure | ||
| cpu.c | ||
| cpus-common.c | ||
| disas.c | ||
| exec-vary.c | ||
| gdbstub.c | ||
| gitdm.config | ||
| hmp-commands-info.hx | ||
| hmp-commands.hx | ||
| iothread.c | ||
| job-qmp.c | ||
| job.c | ||
| memory_ldst.c.inc | ||
| meson.build | ||
| meson_options.txt | ||
| module-common.c | ||
| os-posix.c | ||
| os-win32.c | ||
| qemu-bridge-helper.c | ||
| qemu-edid.c | ||
| qemu-img-cmds.hx | ||
| qemu-img.c | ||
| qemu-io-cmds.c | ||
| qemu-io.c | ||
| qemu-keymap.c | ||
| qemu-nbd.c | ||
| qemu-options-wrapper.h | ||
| qemu-options.h | ||
| qemu-options.hx | ||
| qemu.nsi | ||
| qemu.sasl | ||
| replication.c | ||
| replication.h | ||
| thunk.c | ||
| trace-events | ||
| version.rc | ||
README.rst
=========== QEMU README =========== QEMU is a generic and open source machine & userspace emulator and virtualizer. QEMU is capable of emulating a complete machine in software without any need for hardware virtualization support. By using dynamic translation, it achieves very good performance. QEMU can also integrate with the Xen and KVM hypervisors to provide emulated hardware while allowing the hypervisor to manage the CPU. With hypervisor support, QEMU can achieve near native performance for CPUs. When QEMU emulates CPUs directly it is capable of running operating systems made for one machine (e.g. an ARMv7 board) on a different machine (e.g. an x86_64 PC board). QEMU is also capable of providing userspace API virtualization for Linux and BSD kernel interfaces. This allows binaries compiled against one architecture ABI (e.g. the Linux PPC64 ABI) to be run on a host using a different architecture ABI (e.g. the Linux x86_64 ABI). This does not involve any hardware emulation, simply CPU and syscall emulation. QEMU aims to fit into a variety of use cases. It can be invoked directly by users wishing to have full control over its behaviour and settings. It also aims to facilitate integration into higher level management layers, by providing a stable command line interface and monitor API. It is commonly invoked indirectly via the libvirt library when using open source applications such as oVirt, OpenStack and virt-manager. QEMU as a whole is released under the GNU General Public License, version 2. For full licensing details, consult the LICENSE file. Building ======== QEMU is multi-platform software intended to be buildable on all modern Linux platforms, OS-X, Win32 (via the Mingw64 toolchain) and a variety of other UNIX targets. The simple steps to build QEMU are: .. code-block:: shell mkdir build cd build ../configure make Additional information can also be found online via the QEMU website: * `<https://qemu.org/Hosts/Linux>`_ * `<https://qemu.org/Hosts/Mac>`_ * `<https://qemu.org/Hosts/W32>`_ Submitting patches ================== The QEMU source code is maintained under the GIT version control system. .. code-block:: shell git clone https://git.qemu.org/git/qemu.git When submitting patches, one common approach is to use 'git format-patch' and/or 'git send-email' to format & send the mail to the qemu-devel@nongnu.org mailing list. All patches submitted must contain a 'Signed-off-by' line from the author. Patches should follow the guidelines set out in the CODING_STYLE.rst file. Additional information on submitting patches can be found online via the QEMU website * `<https://qemu.org/Contribute/SubmitAPatch>`_ * `<https://qemu.org/Contribute/TrivialPatches>`_ The QEMU website is also maintained under source control. .. code-block:: shell git clone https://git.qemu.org/git/qemu-web.git * `<https://www.qemu.org/2017/02/04/the-new-qemu-website-is-up/>`_ A 'git-publish' utility was created to make above process less cumbersome, and is highly recommended for making regular contributions, or even just for sending consecutive patch series revisions. It also requires a working 'git send-email' setup, and by default doesn't automate everything, so you may want to go through the above steps manually for once. For installation instructions, please go to * `<https://github.com/stefanha/git-publish>`_ The workflow with 'git-publish' is: .. code-block:: shell $ git checkout master -b my-feature $ # work on new commits, add your 'Signed-off-by' lines to each $ git publish Your patch series will be sent and tagged as my-feature-v1 if you need to refer back to it in the future. Sending v2: .. code-block:: shell $ git checkout my-feature # same topic branch $ # making changes to the commits (using 'git rebase', for example) $ git publish Your patch series will be sent with 'v2' tag in the subject and the git tip will be tagged as my-feature-v2. Bug reporting ============= The QEMU project uses Launchpad as its primary upstream bug tracker. Bugs found when running code built from QEMU git or upstream released sources should be reported via: * `<https://bugs.launchpad.net/qemu/>`_ If using QEMU via an operating system vendor pre-built binary package, it is preferable to report bugs to the vendor's own bug tracker first. If the bug is also known to affect latest upstream code, it can also be reported via launchpad. For additional information on bug reporting consult: * `<https://qemu.org/Contribute/ReportABug>`_ ChangeLog ========= For version history and release notes, please visit `<https://wiki.qemu.org/ChangeLog/>`_ or look at the git history for more detailed information. Contact ======= The QEMU community can be contacted in a number of ways, with the two main methods being email and IRC * `<mailto:qemu-devel@nongnu.org>`_ * `<https://lists.nongnu.org/mailman/listinfo/qemu-devel>`_ * #qemu on irc.oftc.net Information on additional methods of contacting the community can be found online via the QEMU website: * `<https://qemu.org/Contribute/StartHere>`_