x86: qemu: add documentaion for the fw_cfg interface

Document the usage of 'qfw' command Signed-off-by: Miao Yan <yanmiaobest@gmail.com> Reviewed-by: Simon Glass <sjg@chromium.org> Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

x86: qemu: add documentaion for the fw_cfg interface
Document the usage of 'qfw' command Signed-off-by: Miao Yan <yanmiaobest@gmail.com> Reviewed-by: Simon Glass <sjg@chromium.org> Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Miao Yan · Bin Meng
1 parent 3c30fd6ae2
Showing 1 changed file with 31 additions and 3 deletions Side-by-side Diff
doc/README.x86
@@ -295,9 +295,37 @@
 If you want to check both consoles, use '-serial stdio'.
  
 Multicore is also supported by QEMU via '-smp n' where n is the number of cores
-to instantiate. Currently the default U-Boot built for QEMU supports 2 cores.
-In order to support more cores, you need add additional cpu nodes in the device
-tree and change CONFIG_MAX_CPUS accordingly.
+to instantiate. Note, the maximum supported CPU number in QEMU is 255.
+
+The fw_cfg interface in QEMU also provides information about kernel data, initrd,
+command-line arguments and more. U-Boot supports directly accessing these informtion
+from fw_cfg interface, this saves the time of loading them from hard disk or
+network again, through emulated devices. To use it , simply providing them in
+QEMU command line:
+
+$ qemu-system-i386 -nographic -bios path/to/u-boot.rom -m 1024 -kernel /path/to/bzImage
+    -append 'root=/dev/ram console=ttyS0' -initrd /path/to/initrd -smp 8
+
+Note: -initrd and -smp are both optional
+
+Then start QEMU, in U-Boot command line use the following U-Boot command to setup kernel:
+
+ => qfw
+qfw - QEMU firmware interface
+
+Usage:
+qfw <command>
+    - list                             : print firmware(s) currently loaded
+    - cpus                             : print online cpu number
+    - load <kernel addr> <initrd addr> : load kernel and initrd (if any) and setup for zboot
+
+=> qfw load
+loading kernel to address 01000000 size 5d9d30 initrd 04000000 size 1b1ab50
+
+Here the kernel (bzImage) is loaded to 01000000 and initrd is to 04000000. Then, 'zboot'
+can be used to boot the kernel:
+
+=> zboot 02000000 - 04000000 1b1ab50
  
 CPU Microcode
 -------------
...	...	@@ -295,9 +295,37 @@
295	295	If you want to check both consoles, use '-serial stdio'.
296	296
297	297	Multicore is also supported by QEMU via '-smp n' where n is the number of cores
298		-to instantiate. Currently the default U-Boot built for QEMU supports 2 cores.
299		-In order to support more cores, you need add additional cpu nodes in the device
300		-tree and change CONFIG_MAX_CPUS accordingly.
	298	+to instantiate. Note, the maximum supported CPU number in QEMU is 255.
	299	+
	300	+The fw_cfg interface in QEMU also provides information about kernel data, initrd,
	301	+command-line arguments and more. U-Boot supports directly accessing these informtion
	302	+from fw_cfg interface, this saves the time of loading them from hard disk or
	303	+network again, through emulated devices. To use it , simply providing them in
	304	+QEMU command line:
	305	+
	306	+$ qemu-system-i386 -nographic -bios path/to/u-boot.rom -m 1024 -kernel /path/to/bzImage
	307	+ -append 'root=/dev/ram console=ttyS0' -initrd /path/to/initrd -smp 8
	308	+
	309	+Note: -initrd and -smp are both optional
	310	+
	311	+Then start QEMU, in U-Boot command line use the following U-Boot command to setup kernel:
	312	+
	313	+ => qfw
	314	+qfw - QEMU firmware interface
	315	+
	316	+Usage:
	317	+qfw <command>
	318	+ - list : print firmware(s) currently loaded
	319	+ - cpus : print online cpu number
	320	+ - load <kernel addr> <initrd addr> : load kernel and initrd (if any) and setup for zboot
	321	+
	322	+=> qfw load
	323	+loading kernel to address 01000000 size 5d9d30 initrd 04000000 size 1b1ab50
	324	+
	325	+Here the kernel (bzImage) is loaded to 01000000 and initrd is to 04000000. Then, 'zboot'
	326	+can be used to boot the kernel:
	327	+
	328	+=> zboot 02000000 - 04000000 1b1ab50
301	329
302	330	CPU Microcode
303	331	-------------