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On Saturday, 13 July 2019 23:03:11 BST Mick wrote: |
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> Unlike my old Intel which lights up like a christmas tree with "Vulnerable, |
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> no microcode found" because Intel has thrown its users to the kerb, both |
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> AMDs show "Not Vulnerable" and for some of the vulnerabilities it reports: |
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> |
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> (your CPU vendor reported your CPU model as not vulnerable) |
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This last line made me think a bit more. Scratching around I see there are |
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separate patch files with AMD microcode updates offered for the various CPU |
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families. My simplistic assumption so far has been *all* CPUs of a certain |
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family will apply the corresponding patch file microcode update, either via a |
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new UEFI/BIOS firmware, or via the OS. |
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Clearly this is not so. If I remove 'amd-ucode/microcode_amd_fam15h.bin' from |
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my kernel firmware directive completely, or add amd-ucode/ patch files for |
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every family, or even try to manually reload the microcode: |
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echo 1 > /sys/devices/system/cpu/microcode/reload |
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there is no change in dmesg. Clearly my CPU does not load any microcode |
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update, other than what might be already available in the old UEFI MoBo |
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firmware and this is loaded before the OS starts booting. |
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|
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Then I came across this old message regarding Piledriver CPUs: |
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https://lists.debian.org/debian-security/2016/03/msg00084.html |
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The post refers to model 2 of cpu family 21. Not all models in the same |
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family, only model 2. So I am thinking although patch files are named per CPU |
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family, whether they are applicable and applied as an update to the CPU is |
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probably determined by the particular CPU *model*. Logically, errata in |
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previous CPU revisions may have been fixed in later models of the same family |
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and therefore such microcode updates would not be needed. When offered by the |
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OS the CPU won't select to have them applied. |
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This explains why my AMD models, which are later revisions of the same 15h |
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family do not apply any microcode updates - they don't need them. |
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Please share if you know differently and thank you all for your responses. |
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-- |
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Regards, |
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Mick |