Messages in this thread | | | From | Piotr Dąbrowski <> | Date | Tue, 5 Jan 2016 01:27:21 +0100 | Subject | Re: new cmdline parameter disable_cpu_features= (microcode update?) |
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Thank you for your reply.
> You cannot change the microcode patches - they're supplied by the CPU > vendors as is and are signed/encrypted.
Is the microcode's header encrypted too? I thought there are two Processor Flags fields ('pf') available [1]. Are they what I think they are? Is the header signed too, or only the actual microcode blob below the headers is? Sorry if I get it all wrong and there is no use for further discussion.
Do you think there is any point in actually implementing the kernel-only disable_cpu_features= option upstream and then somehow convince the userland to respect flags reported by the kernel instead of those from the CPU?
[1] arch/x86/include/asm/microcode_intel.h: struct microcode_header_intel { unsigned int hdrver; unsigned int rev; unsigned int date; unsigned int sig; unsigned int cksum; unsigned int ldrver; unsigned int pf; unsigned int datasize; unsigned int totalsize; unsigned int reserved[3]; }; [...] /* microcode format is extended from prescott processors */ struct extended_signature { unsigned int sig; unsigned int pf; unsigned int cksum; };
Best Regards, Piotr Dąbrowski
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