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Date: Wed, 24 Aug 2022 21:27:55 +0200 From: Borislav Petkov <bp@...en8.de> To: Ashok Raj <ashok.raj@...el.com> Cc: Thomas Gleixner <tglx@...utronix.de>, Tony Luck <tony.luck@...el.com>, Dave Hansen <dave.hansen@...el.com>, LKML Mailing List <linux-kernel@...r.kernel.org>, X86-kernel <x86@...nel.org>, Andy Lutomirski <luto@...capital.net>, Tom Lendacky <thomas.lendacky@....com>, Jacon Jun Pan <jacob.jun.pan@...el.com> Subject: Re: [PATCH v3 1/5] x86/microcode/intel: Check against CPU signature before saving microcode On Tue, Aug 23, 2022 at 11:13:13AM +0000, Ashok Raj wrote: > > > patch1: > > > fms3 <--- header FMS > > > ... > > > ext_sig: > > > fms1 > > > fms2 > > > > > > patch2: new > > > fms2 <--- header FMS > > > > > > Current code takes only fms3 and checks with patch2 fms2. > > > > So, find_matching_signature() does all the signatures matching and > > scanning already. If anything, that function should tell its callers > > whether the patch it is looking at - the fms2 one - should replace the > > current one or not. > > > > I.e., all the logic to say how strong a patch match is, should be > > concentrated there. And then the caller will do the according action. > > I updated the commit log accordingly. Basically find_matching_signature() > is only intended to find a CPU's sig/pf against a microcode image and not > intended to compare between two different images. Err, what? find_matching_signature() looks at fmt3 - your example above - and then goes and looks at ext_sig. Also your example above. So you can teach that function to say with a *separate* return value "replace current patch with this new patch because this new patch is a better fit." -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette
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