Messages in this thread | | | Date | Tue, 17 Nov 2020 10:25:18 +0800 | From | Chen Yu <> | Subject | Re: [PATCH][v2] x86/microcode/intel: check cpu stepping and processor flag before saving microcode |
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Hi Boris, thanks for taking a look, On Mon, Nov 16, 2020 at 01:27:35PM +0100, Borislav Petkov wrote: > ( drop stable@ from Cc because this is not how fixes get added to stable@ ) > > On Fri, Nov 13, 2020 at 09:59:23AM +0800, Chen Yu wrote: > > Currently scan_microcode() leverages microcode_matches() to check if the > > microcode matches the CPU by comparing the family and model. However before > > saving the microcode in scan_microcode(), the processor stepping and flag > > of the microcode signature should also be considered in order to avoid > > incompatible update and caused the failure of microcode update. > > This is going in the right direction but needs to take care of one > more angle. I've extended your fix to the version below. Lemme know if > something's not clear or still missing. > This patch works for me. Besides I have one question about adding the signature check in save_mc_for_early(): > --- > From: Chen Yu <yu.c.chen@intel.com> > Date: Fri, 13 Nov 2020 09:59:23 +0800 > Subject: [PATCH] x86/microcode/intel: Check patch signature before saving microcode for early loading > > Currently, scan_microcode() leverages microcode_matches() to check > if the microcode matches the CPU by comparing the family and model. > However, the processor stepping and flags of the microcode signature > should also be considered when saving a microcode patch for early > update. > > Use find_matching_signature() in scan_microcode() and get rid of the > now-unused microcode_matches() which is a good cleanup in itself. > > Complete the verification of the patch being saved for early loading in > save_microcode_patch() directly. This needs to be done there too because > save_mc_for_early() will call save_microcode_patch() too. > If I understand correctly, the only place that invokes save_mc_for_early() is in generic_load_microcode(). While in generic_load_microcode() only microcode has a newer version will be saved by checking has_newer_microcode(), and this function leverages find_matching_signature() to check if the candidate is of the same signature. So when it comes to save_microcode_patch(), the signature already matches. In case save_mc_for_early() will be invoked by other function in the future, it is okay to add this check too.
thanks, Chenyu
> > -- > Regards/Gruss, > Boris. > > https://people.kernel.org/tglx/notes-about-netiquette
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