mirror of https://github.com/xemu-project/xemu.git
e2a5d9b3d9
The AHCI spec states that: For NCQ, PxCI is cleared on command queued successfully. For non-NCQ, PxCI is cleared on command completed successfully. (A non-NCQ command that completes with error does not clear PxCI.) The current QEMU implementation either clears PxCI in check_cmd(), or in ahci_cmd_done(). check_cmd() will clear PxCI for a command if handle_cmd() returns 0. handle_cmd() will return -1 if BUSY or DRQ is set. The QEMU implementation for NCQ commands will currently not set BUSY or DRQ, so they will always have PxCI cleared by handle_cmd(). ahci_cmd_done() will never even get called for NCQ commands. Non-NCQ commands are executed by ide_bus_exec_cmd(). Non-NCQ commands in QEMU are implemented either in a sync or in an async way. For non-NCQ commands implemented in a sync way, the command handler will return true, and when ide_bus_exec_cmd() sees that a command handler returns true, it will call ide_cmd_done() (which will call ahci_cmd_done()). For a command implemented in a sync way, ahci_cmd_done() will do nothing (since busy_slot is not set). Instead, after ide_bus_exec_cmd() has finished, check_cmd() will clear PxCI for these commands. For non-NCQ commands implemented in an async way (using either aiocb or pio_aiocb), the command handler will return false, ide_bus_exec_cmd() will not call ide_cmd_done(), instead it is expected that the async callback function will call ide_cmd_done() once the async command is done. handle_cmd() will set busy_slot, if and only if BUSY or DRQ is set, and this is checked _after_ ide_bus_exec_cmd() has returned. handle_cmd() will return -1, so check_cmd() will not clear PxCI. When the async callback calls ide_cmd_done() (which will call ahci_cmd_done()), it will see that busy_slot is set, and ahci_cmd_done() will clear PxCI. This seems racy, since busy_slot is set _after_ ide_bus_exec_cmd() has returned. The callback might come before busy_slot gets set. And it is quite confusing that ahci_cmd_done() will be called for all non-NCQ commands when the command is done, but will only clear PxCI in certain cases, even though it will always write a D2H FIS and raise an IRQ. Even worse, in the case where ahci_cmd_done() does not clear PxCI, it still raises an IRQ. Host software might thus read an old PxCI value, since PxCI is cleared (by check_cmd()) after the IRQ has been raised. Try to simplify this by always setting busy_slot for non-NCQ commands, such that ahci_cmd_done() will always be responsible for clearing PxCI for non-NCQ commands. For NCQ commands, clear PxCI when we receive the D2H FIS, but before raising the IRQ, see AHCI 1.3.1, section 5.3.8, states RegFIS:Entry and RegFIS:ClearCI. Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com> Message-id: 20230609140844.202795-5-nks@flawful.org Signed-off-by: John Snow <jsnow@redhat.com> |
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| authz | ||
| backends | ||
| block | ||
| bsd-user | ||
| chardev | ||
| common-user | ||
| configs | ||
| contrib | ||
| crypto | ||
| disas | ||
| docs | ||
| dump | ||
| ebpf | ||
| fpu | ||
| fsdev | ||
| gdb-xml | ||
| gdbstub | ||
| host/include | ||
| hw | ||
| include | ||
| io | ||
| libdecnumber | ||
| linux-headers | ||
| linux-user | ||
| migration | ||
| monitor | ||
| nbd | ||
| net | ||
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| python | ||
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| softmmu | ||
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| ui | ||
| util | ||
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| COPYING | ||
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| Kconfig | ||
| Kconfig.host | ||
| LICENSE | ||
| MAINTAINERS | ||
| Makefile | ||
| README.rst | ||
| VERSION | ||
| block.c | ||
| blockdev-nbd.c | ||
| blockdev.c | ||
| blockjob.c | ||
| configure | ||
| cpu.c | ||
| cpus-common.c | ||
| event-loop-base.c | ||
| gitdm.config | ||
| hmp-commands-info.hx | ||
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| iothread.c | ||
| job-qmp.c | ||
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| memory_ldst.c.inc | ||
| meson.build | ||
| meson_options.txt | ||
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| os-win32.c | ||
| page-vary-common.c | ||
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| pythondeps.toml | ||
| 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 | ||
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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. 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://wiki.qemu.org/Hosts/Linux>`_ * `<https://wiki.qemu.org/Hosts/Mac>`_ * `<https://wiki.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://wiki.qemu.org/Contribute/SubmitAPatch>`_ * `<https://wiki.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 GitLab issues to track bugs. Bugs found when running code built from QEMU git or upstream released sources should be reported via: * `<https://gitlab.com/qemu-project/qemu/-/issues>`_ 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 GitLab. For additional information on bug reporting consult: * `<https://wiki.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://wiki.qemu.org/Contribute/StartHere>`_