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[PATCH v1 13/13] qemu-options: bring the kernel and image options togeth
From: |
Alex Bennée |
Subject: |
[PATCH v1 13/13] qemu-options: bring the kernel and image options together |
Date: |
Mon, 25 Jul 2022 15:05:20 +0100 |
How to control the booting of QEMU is often a source of confusion for
users. Bring the options that control this together in the manual
pages and add some verbiage to describe when each option is
appropriate. This attempts to codify some of the knowledge expressed
in:
https://stackoverflow.com/questions/58420670/qemu-bios-vs-kernel-vs-device-loader-file/58434837#58434837
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20220707151037.397324-1-alex.bennee@linaro.org>
---
qemu-options.hx | 96 +++++++++++++++++++++++++++++++++++++++----------
1 file changed, 78 insertions(+), 18 deletions(-)
diff --git a/qemu-options.hx b/qemu-options.hx
index 8e17c5064a..3f23a42fa8 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1585,13 +1585,6 @@ SRST
Use file as SecureDigital card image.
ERST
-DEF("pflash", HAS_ARG, QEMU_OPTION_pflash,
- "-pflash file use 'file' as a parallel flash image\n", QEMU_ARCH_ALL)
-SRST
-``-pflash file``
- Use file as a parallel flash image.
-ERST
-
DEF("snapshot", 0, QEMU_OPTION_snapshot,
"-snapshot write to temporary files instead of disk image files\n",
QEMU_ARCH_ALL)
@@ -3684,12 +3677,67 @@ DEFHEADING()
#endif
-DEFHEADING(Linux/Multiboot boot specific:)
+DEFHEADING(Boot Image or Kernel specific:)
+SRST
+There are broadly 4 ways you can boot a system with QEMU.
+
+ - specify a firmware and let it control finding a kernel
+ - specify a firmware and pass a hint to the kernel to boot
+ - direct kernel image boot
+ - manually load files into the guest's address space
+
+The third method is useful for quickly testing kernels but as there is
+no firmware to pass configuration information to the kernel the
+hardware must either be probeable, the kernel built for the exact
+configuration or passed some configuration data (e.g. a DTB blob)
+which tells the kernel what drivers it needs. This exact details are
+often hardware specific.
+
+The final method is the most generic way of loading images into the
+guest address space and used mostly for ``bare metal`` type
+development where the reset vectors of the processor are taken into
+account.
+
+ERST
+
SRST
-When using these options, you can use a given Linux or Multiboot kernel
-without installing it in the disk image. It can be useful for easier
-testing of various kernels.
+For x86 machines and some other architectures ``-bios`` will generally
+do the right thing with whatever it is given. For other machines the
+more strict ``-pflash`` option needs an image that is sized for the
+flash device for the given machine type.
+
+Please see the :ref:`system-targets-ref` section of the manual for
+more detailed documentation.
+
+ERST
+
+DEF("bios", HAS_ARG, QEMU_OPTION_bios, \
+ "-bios file set the filename for the BIOS\n", QEMU_ARCH_ALL)
+SRST
+``-bios file``
+ Set the filename for the BIOS.
+ERST
+
+DEF("pflash", HAS_ARG, QEMU_OPTION_pflash,
+ "-pflash file use 'file' as a parallel flash image\n", QEMU_ARCH_ALL)
+SRST
+``-pflash file``
+ Use file as a parallel flash image.
+ERST
+
+SRST
+
+The kernel options were designed to work with Linux kernels although
+other things (like hypervisors) can be packaged up as a kernel
+executable image. The exact format of a executable image is usually
+architecture specific.
+
+The way in which the kernel is started (what address it is loaded at,
+what if any information is passed to it via CPU registers, the state
+of the hardware when it is started, and so on) is also architecture
+specific. Typically it follows the specification laid down by the
+Linux kernel for how kernels for that architecture must be started.
ERST
@@ -3729,6 +3777,25 @@ SRST
kernel on boot.
ERST
+SRST
+
+Finally you can also manually load images directly into the address
+space of the guest. This is most useful for developers who already
+know the layout of their guest and take care to ensure something sane
+will happen when the reset vector executes.
+
+The generic loader can be invoked by using the loader device:
+
+``-device
loader,addr=<addr>,data=<data>,data-len=<data-len>[,data-be=<data-be>][,cpu-num=<cpu-num>]``
+
+there is also the guest loader which operates in a similar way but
+tweaks the DTB so a hypervisor loaded via ``-kernel`` can find where
+the guest image is:
+
+``-device
guest-loader,addr=<addr>[,kernel=<path>,[bootargs=<arguments>]][,initrd=<path>]``
+
+ERST
+
DEFHEADING()
DEFHEADING(Debug/Expert options:)
@@ -4179,13 +4246,6 @@ SRST
To list all the data directories, use ``-L help``.
ERST
-DEF("bios", HAS_ARG, QEMU_OPTION_bios, \
- "-bios file set the filename for the BIOS\n", QEMU_ARCH_ALL)
-SRST
-``-bios file``
- Set the filename for the BIOS.
-ERST
-
DEF("enable-kvm", 0, QEMU_OPTION_enable_kvm, \
"-enable-kvm enable KVM full virtualization support\n",
QEMU_ARCH_ARM | QEMU_ARCH_I386 | QEMU_ARCH_MIPS | QEMU_ARCH_PPC |
--
2.30.2
- [PATCH v1 02/13] gitlab: show testlog.txt contents when cirrus/custom-runner jobs fail, (continued)
- [PATCH v1 02/13] gitlab: show testlog.txt contents when cirrus/custom-runner jobs fail, Alex Bennée, 2022/07/25
- [PATCH v1 04/13] .cirrus.yml: Change winsymlinks to 'native', Alex Bennée, 2022/07/25
- [PATCH v1 05/13] .gitlab-ci.d/windows.yml: Enable native Windows symlink, Alex Bennée, 2022/07/25
- [PATCH v1 06/13] semihosting: Don't return negative values on qemu_semihosting_console_write() failure, Alex Bennée, 2022/07/25
- [PATCH v1 07/13] semihosting: Don't copy buffer after console_write(), Alex Bennée, 2022/07/25
- [PATCH v1 08/13] semihosting: Check for errors on SET_ARG(), Alex Bennée, 2022/07/25
- [PATCH v1 11/13] tests/tcg/s390x: Test unaligned accesses to lowcore, Alex Bennée, 2022/07/25
- [PATCH v1 10/13] qapi: Add exit-failure PanicAction, Alex Bennée, 2022/07/25
- [PATCH v1 13/13] qemu-options: bring the kernel and image options together,
Alex Bennée <=
- [PATCH v1 12/13] docs/devel: fix description of OBJECT_DECLARE_SIMPLE_TYPE, Alex Bennée, 2022/07/25
- [PATCH v1 03/13] gitlab: drop 'containers-layer2' stage, Alex Bennée, 2022/07/25
- [PATCH v1 09/13] semihosting: Fix handling of buffer in TARGET_SYS_TMPNAM, Alex Bennée, 2022/07/25