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On A-profile, PSR bits [15:10][26:25] are always the IT state bits. On M-profile, some of the reserved encodings of the IT state are used to instead indicate partial progress through instructions that were interrupted partway through by an exception and can be resumed. These resumable instructions fall into two categories: (1) load/store multiple instructions, where these bits are called "ICI" and specify the register in the ldm/stm list where execution should resume. (Specifically: LDM, STM, VLDM, VSTM, VLLDM, VLSTM, CLRM, VSCCLRM.) (2) MVE instructions subject to beatwise execution, where these bits are called "ECI" and specify which beats in this and possibly also the following MVE insn have been executed. There are also a few insns (LE, LETP, and BKPT) which do not use the ICI/ECI bits but must leave them alone. Otherwise, we should raise an INVSTATE UsageFault for any attempt to execute an insn with non-zero ICI/ECI bits. So far we have been able to ignore ECI/ICI, because the architecture allows the IMPDEF choice of "always restart load/store multiple from the beginning regardless of ICI state", so the only thing we have been missing is that we don't raise the INVSTATE fault for bad guest code. However, MVE requires that we honour ECI bits and do not rexecute beats of an insn that have already been executed. Add the support in the decoder for handling ECI/ICI: * identify the ECI/ICI case in the CONDEXEC TB flags * when a load/store multiple insn succeeds, it updates the ECI/ICI state (both in DisasContext and in the CPU state), and sets a flag to say that the ECI/ICI state was handled * if we find that the insn we just decoded did not handle the ECI/ICI state, we delete all the code that we just generated for it and instead emit the code to raise the INVFAULT. This allows us to avoid having to update every non-MVE non-LDM/STM insn to make it check for "is ECI/ICI set?". We continue with our existing IMPDEF choice of not caring about the ICI state for the load/store multiples and simply restarting them from the beginning. Because we don't allow interrupts in the middle of an insn, the only way we would see this state is if the guest set ICI manually on return from an exception handler, so it's a corner case which doesn't merit optimisation. ICI update for LDM/STM is simple -- it always zeroes the state. ECI update for MVE beatwise insns will be a little more complex, since the ECI state may include information for the following insn. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Message-id: 20210614151007.4545-5-peter.maydell@linaro.org
=========== 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. Documentation ============= Documentation can be found hosted online at `<https://www.qemu.org/documentation/>`_. The documentation for the current development version that is available at `<https://www.qemu.org/docs/master/>`_ is generated from the ``docs/`` folder in the source tree, and is built by `Sphinx <https://www.sphinx-doc.org/en/master/>_`. 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://gitlab.com/qemu-project/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 `style section <https://www.qemu.org/docs/master/devel/style.html>` of the Developers Guide. 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://gitlab.com/qemu-project/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>`_