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Aravind Gopalakrishnan
4c5e3a8e84
Some cleanups to the documentation- - Remove unnecessary steps listed to apply ucode using initrd. - Condense 'Misc notes' section as well Suggested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Signed-off-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@amd.com>
91 lines
3.6 KiB
Plaintext
91 lines
3.6 KiB
Plaintext
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AMD Microcode Container File format
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-------------------------------------------------
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Author:
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Aravind [dot] Gopalakrishnan [at] amd [dot] com
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Initial version:
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July 2014
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Updated:
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October 2014
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-------------------------------------------------
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Intro to AMD Container Files:
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-----------------------------
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* AMD provides microcode patch support for processors belonging to AMD
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processor families 10h, 11h, 12h, 14h, and 15h.
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* There is one single file (container file) containing all microcode patches
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for AMD families 10h - 14h processors. [microcode_amd.bin]
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* For AMD processor families 15h and later, there is a separate container file
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for each family. (e.g. microcode_amd_fam15h.bin)
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* Microcode patches are not incremental, therefore you only need to make
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sure you have the latest container file for your AMD processor family.
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* One can find the latest AMD microcode containers from [1], [2]
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Mutual Exclusivity Rule of AMD containers:
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* The patches for families 10h - 14h are guaranteed to be only on
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microcode_amd.bin
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* Similarly, patches for family 15h and later will only be on their respective
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family specific container file. (e.g. microcode_amd_fam15h.bin)
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* This is because, the processes and scripts used to create container files
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ensure that there is no mix-up
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Microcode patch header structure:
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---------------------------------
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struct __packed microcode_header_amd {
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uint32_t data_code;
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uint32_t patch_id;
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uint8_t mc_patch_data_id[2];
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uint8_t mc_patch_data_len;
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uint8_t init_flag;
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uint32_t mc_patch_data_checksum;
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uint32_t nb_dev_id;
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uint32_t sb_dev_id;
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uint16_t processor_rev_id;
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uint8_t nb_rev_id;
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uint8_t sb_rev_id;
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uint8_t bios_api_rev;
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uint8_t reserved1[3];
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uint32_t match_reg[8];
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}
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More details about microcode patch header are typically not exposed to public.
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Apply microcode updates using initrd:
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-------------------------------------
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Initrd images can be modified to contain AMD microcode containers in cpio
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format at the start of the image.
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Following example shows how to generate a combined initrd
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Note: initrd-<val> could be different on your machine. Substitute accordingly
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Example System base: Ubuntu 13.04 with 3.8.0-30-generic kernel
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1. mkdir initrd-for-xen-with_append
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2. cd initrd-for-xen-with_append
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3. mkdir -p kernel/x86/microcode
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4. cat /lib/firmware/amd-ucode/microcode_amd.bin \
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/lib/firmware/amd-ucode/microcode_amd_fam15h.bin > \
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kernel/x86/microcode/AuthenticAMD.bin
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5. find . | cpio -o -H newc > ucode.cpio
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6. cat ucode.cpio /boot/initrd.img-3.8.0-30-generic > /boot/initrd_for_xen_with_ucode
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7. On grub.cfg, provide the above initrd name as module.
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8. Use 'ucode=scan' option as Xen boot parameter.
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Misc Notes:
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-----------
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It is not recommended to concatenate two(or more) container files of
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the same kind. (e.g. two microcode_amd_fam15h.bin) since the hypervisor
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will apply a patch as and when it determines that it is a 'good fit'.
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Once the patch is applied, further parsing of the file is skipped.
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Therefore, if a subsequent container file has a newer/updated patch, that
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patch will be ignored.
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In cases where users are not sure about provenance of containers
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they should obtain a "good" set by downloading them from source links
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[1], [2] since it's not guaranteed that the latest patch will be applied.
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Reference(s):
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-------------
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[1] http://www.amd64.org/microcode.html
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[2] https://git.kernel.org/cgit/linux/kernel/git/firmware/linux-firmware.git/tree/amd-ucode
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[3] http://lxr.free-electrons.com/source/Documentation/x86/early-microcode.txt
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