Messages in this thread | | | Date | Wed, 7 Dec 2022 16:05:19 -0800 | From | Ashok Raj <> | Subject | Re: [Patch V1 4/7] x86/microcode/core: Take a snapshot before and after applying microcode |
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On Wed, Dec 07, 2022 at 09:25:54PM +0100, Borislav Petkov wrote: > On Tue, Nov 29, 2022 at 01:08:29PM -0800, Ashok Raj wrote: > > The kernel caches features about each CPU's features at boot in an > > x86_capability[] structure. The microcode update takes one snapshot and > > compares it with the saved copy at boot. > > > > However, the capabilities in the boot copy can be turned off as a result of > > certain command line parameters or configuration restrictions. This can > > cause a mismatch when comparing the values before and after the microcode > > update. > > Hmm, but if that has happened, the capabilities will be turned off in > your @orig argument below? > > Or are you saying that this copy_cpu_caps() read before the update will > overwrite the cleared bits with the their actual values from CPUID so > that what you really wanna compare here is *hardware* CPUID bits before > and after and not our potentially modified copy? > > I.e., some bit in CPUID is 1 and we have cleared it in our copy. > > Close?
Correct.
> > If so, then this should be specifically called out in the commit > message.
Sounds good, I can certainly add it when I repost.
> > > +static void copy_cpu_caps(struct cpuinfo_x86 *info) > > If anything, that function should be called > > store_cpu_caps() > The names sounds more fitting, I can change it as suggested.
Cheers, Ashok
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