Fix VMware esx problem hyperthreading unmitigated
2Here's how to Fix VMware esx problem hyperthreading unmitigated.
VMware esx problem hyperthreading unmitigated is a warning message that appears on ESXi hosts after installing patches to mitigate the L1 Terminal Fault (L1TF) vulnerability (CVE-2018-3646). This vulnerability affects Intel processors that support hyperthreading and can allow an attacker to access sensitive information from other virtual machines or the hypervisor. The patches provide a partial mitigation by isolating the logical processors of a hyperthreaded core from different security domains. However, this mitigation is not enabled by default and requires a manual configuration change and a host reboot. The warning message is intended to alert the users about the potential vulnerability and the available mitigation option.
To fix this warning message, you have two options:
- **Enable the full mitigation**: If you want to enable the full mitigation for the L1TF vulnerability, you need to set the ESXi advanced option VMkernel.Boot.hyperthreadingMitigation to true and reboot the host. This will prevent different security domains from sharing a hyperthreaded core and reduce the risk of information leakage. However, this option will also reduce the CPU capacity and performance of your host by up to 50%, depending on your workload.
- **Suppress the warning message**: If you do not want to enable the full mitigation or if you have other security measures in place, you can suppress the warning message by setting the ESXi advanced option UserVars.SuppressHyperthreadWarning to 1. This will hide the warning message from the vSphere Client and the ESXi Shell, but it will not change the security status of your host. You can still view the warning message by running esxcli system settings advanced list -o /UserVars/SuppressHyperthreadWarning in the ESXi Shell.
Note: Before applying any of these options, you need to make sure that your vCenter Server is updated to the latest version that supports the L1TF patches. Otherwise, you may encounter some issues with displaying or configuring the ESXi advanced options.
Source:
(1) Solved: XXX esx.problem.hyperthreading.unmitigated.formatO... - VMware. https://communities.vmware.com/t5/VMware-vSphere-Discussions/XXX-esx-problem-hyperthreading-unmitigated-formatOnHost-not/td-p/2757506.
(2) ESX.Problem.Hyperthreading.Unmitigated - VMware Technology Network VMTN. https://communities.vmware.com/t5/VMware-NSX-Discussions/ESX-Problem-Hyperthreading-Unmitigated/td-p/1396037.
(3) Solved: esx.problem.hyperthreading.unmitigated como resolv... - VMware .... https://communities.vmware.com/t5/Brazilian-Portuguese-Discussions/esx-problem-hyperthreading-unmitigated-como-resolver/td-p/1843101.
i. To enable hyperthreading on ESXi host, follow these steps:
1. Log in to the ESXi host using the vSphere Client.
2. Click on the host name in the left-hand pane.
3. Click on the **Configuration** tab.
4. Click on the **Processors** option under the **Hardware** section.
5. Check the **Enable Intel Hyperthreading Technology** checkbox.
6. Click on the **OK** button.
The ESXi host will now restart. Once the host has restarted, hyperthreading will be enabled.
Here are some things to keep in mind when enabling hyperthreading on ESXi host:
* Hyperthreading can improve performance by allowing each physical CPU core to run two threads simultaneously.
* Enabling hyperthreading can also increase power consumption and heat dissipation.
* Not all applications will benefit from hyperthreading.
It is important to test your applications after enabling hyperthreading to make sure that they are not adversely affected.
Here are some additional tips for enabling hyperthreading on ESXi host:
* Make sure that your CPU supports hyperthreading.
* Enable hyperthreading only if your applications will benefit from it.
* Monitor your power consumption and heat dissipation after enabling hyperthreading.
* Disable hyperthreading if your applications are not benefiting from it or if it is causing performance problems.
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