Messages in this thread | | | Date | Sat, 17 Feb 2018 08:50:53 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86/microcode/intel: Check microcode revision before updating sibling threads |
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* Ashok Raj <ashok.raj@intel.com> wrote:
> After updating microcode on one of the threads in the core, the > thread sibling automatically gets the update since the microcode > resources are shared. Check the ucode revision on the cpu before > performing a ucode update.
s/cpu/CPU
> > Signed-off-by: Ashok Raj <ashok.raj@intel.com> > Cc: X86 ML <x86@kernel.org> > Cc: LKML <linux-kernel@vger.kernel.org> > --- > arch/x86/kernel/cpu/microcode/intel.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c > index 09b95a7..036d1db 100644 > --- a/arch/x86/kernel/cpu/microcode/intel.c > +++ b/arch/x86/kernel/cpu/microcode/intel.c > @@ -776,7 +776,7 @@ static enum ucode_state apply_microcode_intel(int cpu) > { > struct microcode_intel *mc; > struct ucode_cpu_info *uci; > - struct cpuinfo_x86 *c; > + struct cpuinfo_x86 *c = &cpu_data(cpu); > static int prev_rev; > u32 rev; > > @@ -793,6 +793,18 @@ static enum ucode_state apply_microcode_intel(int cpu) > return UCODE_NFOUND; > } > > + rev = intel_get_microcode_revision(); > + /* > + * Its possible the microcode got udpated > + * because its sibling update was done earlier. > + * Skip the udpate in that case. > + */ > + if (rev >= mc->hdr.rev) { > + uci->cpu_sig.rev = rev; > + c->microcode = rev; > + return UCODE_OK; > + }
s/udpate /update
Also, more fundamentally, during microcode early testing, isn't it possible for internal iterations of the microcode to have the same revision, but be different?
This patch would prevent re-loading it - for a seemingly minimal benefit.
Thanks,
Ingo
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