diff options
Diffstat (limited to 'Documentation/x86')
| -rw-r--r-- | Documentation/x86/boot.txt | 41 | ||||
| -rw-r--r-- | Documentation/x86/early-microcode.txt | 43 | ||||
| -rw-r--r-- | Documentation/x86/x86_64/boot-options.txt | 4 |
3 files changed, 83 insertions, 5 deletions
diff --git a/Documentation/x86/boot.txt b/Documentation/x86/boot.txt index 3edb4c2887a..3840b6f28af 100644 --- a/Documentation/x86/boot.txt +++ b/Documentation/x86/boot.txt @@ -57,7 +57,7 @@ Protocol 2.10: (Kernel 2.6.31) Added a protocol for relaxed alignment Protocol 2.11: (Kernel 3.6) Added a field for offset of EFI handover protocol entry point. -Protocol 2.12: (Kernel 3.9) Added the xloadflags field and extension fields +Protocol 2.12: (Kernel 3.8) Added the xloadflags field and extension fields to struct boot_params for for loading bzImage and ramdisk above 4G in 64bit. @@ -390,6 +390,7 @@ Protocol: 2.00+ F Special (0xFF = undefined) 10 Reserved 11 Minimal Linux Bootloader <http://sebastian-plotz.blogspot.de> + 12 OVMF UEFI virtualization stack Please contact <hpa@zytor.com> if you need a bootloader ID value assigned. @@ -1054,6 +1055,44 @@ must have read/write permission; CS must be __BOOT_CS and DS, ES, SS must be __BOOT_DS; interrupt must be disabled; %esi must hold the base address of the struct boot_params; %ebp, %edi and %ebx must be zero. +**** 64-bit BOOT PROTOCOL + +For machine with 64bit cpus and 64bit kernel, we could use 64bit bootloader +and we need a 64-bit boot protocol. + +In 64-bit boot protocol, the first step in loading a Linux kernel +should be to setup the boot parameters (struct boot_params, +traditionally known as "zero page"). The memory for struct boot_params +could be allocated anywhere (even above 4G) and initialized to all zero. +Then, the setup header at offset 0x01f1 of kernel image on should be +loaded into struct boot_params and examined. The end of setup header +can be calculated as follows: + + 0x0202 + byte value at offset 0x0201 + +In addition to read/modify/write the setup header of the struct +boot_params as that of 16-bit boot protocol, the boot loader should +also fill the additional fields of the struct boot_params as described +in zero-page.txt. + +After setting up the struct boot_params, the boot loader can load +64-bit kernel in the same way as that of 16-bit boot protocol, but +kernel could be loaded above 4G. + +In 64-bit boot protocol, the kernel is started by jumping to the +64-bit kernel entry point, which is the start address of loaded +64-bit kernel plus 0x200. + +At entry, the CPU must be in 64-bit mode with paging enabled. +The range with setup_header.init_size from start address of loaded +kernel and zero page and command line buffer get ident mapping; +a GDT must be loaded with the descriptors for selectors +__BOOT_CS(0x10) and __BOOT_DS(0x18); both descriptors must be 4G flat +segment; __BOOT_CS must have execute/read permission, and __BOOT_DS +must have read/write permission; CS must be __BOOT_CS and DS, ES, SS +must be __BOOT_DS; interrupt must be disabled; %rsi must hold the base +address of the struct boot_params. + **** EFI HANDOVER PROTOCOL This protocol allows boot loaders to defer initialisation to the EFI diff --git a/Documentation/x86/early-microcode.txt b/Documentation/x86/early-microcode.txt new file mode 100644 index 00000000000..4aaf0dfb0cb --- /dev/null +++ b/Documentation/x86/early-microcode.txt @@ -0,0 +1,43 @@ +Early load microcode +==================== +By Fenghua Yu <fenghua.yu@intel.com> + +Kernel can update microcode in early phase of boot time. Loading microcode early +can fix CPU issues before they are observed during kernel boot time. + +Microcode is stored in an initrd file. The microcode is read from the initrd +file and loaded to CPUs during boot time. + +The format of the combined initrd image is microcode in cpio format followed by +the initrd image (maybe compressed). Kernel parses the combined initrd image +during boot time. The microcode file in cpio name space is: +kernel/x86/microcode/GenuineIntel.bin + +During BSP boot (before SMP starts), if the kernel finds the microcode file in +the initrd file, it parses the microcode and saves matching microcode in memory. +If matching microcode is found, it will be uploaded in BSP and later on in all +APs. + +The cached microcode patch is applied when CPUs resume from a sleep state. + +There are two legacy user space interfaces to load microcode, either through +/dev/cpu/microcode or through /sys/devices/system/cpu/microcode/reload file +in sysfs. + +In addition to these two legacy methods, the early loading method described +here is the third method with which microcode can be uploaded to a system's +CPUs. + +The following example script shows how to generate a new combined initrd file in +/boot/initrd-3.5.0.ucode.img with original microcode microcode.bin and +original initrd image /boot/initrd-3.5.0.img. + +mkdir initrd +cd initrd +mkdir kernel +mkdir kernel/x86 +mkdir kernel/x86/microcode +cp ../microcode.bin kernel/x86/microcode/GenuineIntel.bin +find .|cpio -oc >../ucode.cpio +cd .. +cat ucode.cpio /boot/initrd-3.5.0.img >/boot/initrd-3.5.0.ucode.img diff --git a/Documentation/x86/x86_64/boot-options.txt b/Documentation/x86/x86_64/boot-options.txt index de38429beb7..e015a83c399 100644 --- a/Documentation/x86/x86_64/boot-options.txt +++ b/Documentation/x86/x86_64/boot-options.txt @@ -112,10 +112,6 @@ Timing This can be used to work around timing problems on multiprocessor systems with not properly synchronized CPUs. - report_lost_ticks - Report when timer interrupts are lost because some code turned off - interrupts for too long. - nohpet Don't use the HPET timer. |