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Wed, 1 Jul 2026 19:02:50 +0000 Message-ID: <03e30d36-1960-4f36-a058-98ce58923344@intel.com> Date: Wed, 1 Jul 2026 12:02:48 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/microcode/intel: Panic on partial microcode update To: Dave Hansen , CC: , , , , , References: <20260630191350.3837-1-chang.seok.bae@intel.com> <4f2a4841-0a73-4f44-aec8-890734660a9c@intel.com> Content-Language: en-US From: "Chang S. 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They also know when it is dangerous to keep the > CPU running. They obviously don't think that this partial update thing > is *THAT* dangerous or they wouldn't have even let the CPU keep > churning. Right? A revision of the spec doc adds some description of the severity, which looks worth referencing here for the review / decision. Spec - https://cdrdv2.intel.com/v1/dl/getContent/782715 There are two bits in MSR_IA32_MCU_STATUS: * Bit 0 indicates a partial update occured * Bit 1 indicates authentication failed _after_ the update was committed and the revision ID was updated. Section 2.7 summarizes the implications: +----------------+----------------+--------------------------+ | partial update | authentication | note / recommendation | +----------------+----------------+--------------------------+ | no | fail | impossible | |----------------+----------------+--------------------------| | yes | success | log the error | |----------------+----------------+--------------------------| | yes | fail | raise a fatal error | +----------------+----------------+--------------------------+ It could be an option to handle those cases separately. But yes, a sane ucode can escalate an unrecoverable condition via #MC. I'll revise V2 to simply taint the kernel (TAINT_WARN) on any of those. Thanks, Chang