More microcode madness – VMware recommends NOT patching

Oy vey.

As a continuation to the Spectre/Meltdown situation VMware had pushed out an update identified as ESXi650-201801402-BG (for 6.5, ESXi600-201801402-BG for 6.0, and ESXi550-201801401-BG for 5.5) that included a VIB for “VMware_bootbank_cpu-microcode_6.5.0-1.38.7526125” which would address the speculative execution issues.

It turns out that in VMware KB 52345 “it has been recommended that VMware remove exposure of the speculative-execution mechanism to virtual machines on ESXi hosts using the affected Intel processors until Intel provides new microcode at a later date.”  Oh… why?  Not sure…

But, here’s something interesting.  Yesterday I posted a benchmark on a ZFS VM with and without this microcode patch running on a (Dell R620 with E5-2640 v1 CPUs) in order to gauge the performance impact of a storage solution running the “fixed” microcode.  The benchmark ran fine with and without the code applied and I went on my way leaving my R620 running the microcode and my Supermicro X9DRI-LN4F+ system running without it.

I had shutdown the R620 as I was done testing only to return later and want to use it again.  I powered the host up and watched ESXi boot but it didn’t reconnect to vCenter.  It can take a bit sometimes so I wasn’t worried about it.  After about 5 minutes I logged into the iDRAC to find that the system was booting up and was just at POST.  Wait… I already booted the system up…

Turns out the machine experienced some fatal errors involving the PCI Express bus and power cycled:

Sigh.  The entry at on Jan 13 at 23:02:28 was the time that the power cycled.  The subsequent 4 errors were me trying the host again later (one boot yielded the 4 errors).

The only thing that changed was the Intel Microcode update via VMware.

Now, that’s not to say I didn’t experience some sort of super coincidental issue, but I did just get done doing decently strenuous benchmarking and everything was fine and this system has been rock solid for about a year.  I looked into it some and identified my LSI 9211-8i as being in slot 1 which it seems the iDRAC system logs are pointing to as having an issue.  Again, nothing was moved or bumped or anything – the server has been in the rack and never touched.  I cleared the logs then removed power from the system for 5 minutes and tried again – so far so good.  The system has been up for 18 – 20 hours now without issue.

I am not sure if this is coincidental or not, but I’ve heard of some reports of issues with the new microcode (though it’s traditionally been in Haswell and Broadwell machines) – for now, you can be I’m not applying microcode updates in production until this is all ironed out.

What a whirlwind!  Thanks for reading!

Author: Jon

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  1. So far the microcode updates seem to be only for gen4 and newer CPUs. Sandy bridge came out in 2011 so Intel might not even release updates for it

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    • Yep that’s what it’s all saying – it’s just extremely odd that I had issues literally after the first reboot and applying the microcode vib… eek!

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  2. That’s pretty interesting. Thanks for sharing. I wonder if something was cached and cold boot cleared it? I’m not a big fan of “coincidence”.

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    • CPU cache is volatile, so it shouldn’t have mattered. It is somewhat concerning… I don’t like coincidence either!

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