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The question on everyone's minds: Does MacOS fix the Intel #KPTI Issue? Why yes, yes it does. Say hello to the "Double Map" since 10.13.2 -- and with some surprises in 10.13.3 (under Developer NDA so can't talk/show you). cc @i0n1c @s1guza @patrickwardlepic.twitter.com/S1YJ9tMS63
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Thanks. Twitter will use this to make your timeline better. UndoUndo
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Haven’t noticed myself, or seen any reports of performance drops in 10.13.2 - does that mean that macOS works around the problem without penalty?
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The performance drop on a system with PCID is minimal. Most Macs have PCID.
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Pre-Haswell Macs don't have PCID.
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Westmere introduced PCID.
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But the KPTI fix for Linux at least doesn't use PCID pre Haswell because it adds an optimization. Lmk if you want the link explaining
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Please share the link.
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PCID only useful with (Haswell & later) INVPCID instruction to help flush individual PCIDs https://patchwork.kernel.org/patch/10078991/
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Is that right that there is need for 10.13.3 for full bug mitigation?
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No, sorry, did not mean to imply that. There are some changes in 10.13.3 but they shouldn't affect the quality of the mitigation _as far as I can see_
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Hi, what decompiler are you using there? Looks absolutely epic...
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Hex-Rays
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Hm, so did that show the processor slowdown?
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the processor doesn't slow down
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Just on macOS it doesn’t slow down? Why would that be? Moving instructions to the OS kernel has shown slowdown in every other patch for this.
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It will have a (not huge) perf impact on all operating systems. There is nothing magic about the Mac fix.
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That’s what I figured. Wonder if anyone noticed a small dip in some workloads. SQL can be down quite a bit here.
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Has anyone checked whether this fix was part of the recent security update for macOS Sierra (or even El Capitan) as well?
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This does NOT appear to be part of the Sierra fix, see e.g. (image) fully patched 10.12.6 _idt64_sysenter does not have the extra code. Time for stragglers to update I think.pic.twitter.com/sLnOUNW7Ow
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