Intel TXT and UEFI compatibility

[agold]

Hi,

I've been working on a UEFI bootloader that leverages Intel TXT. So far I'm able to boot into my MLE without issue. However I need to be able to use UEFI's protocols and boot services within the MLE. This means I have to restore some of the UEFI machine state (GDT, IDT, Page Tables, etc.) after entering the MLE.

For the most part this seems to work fine up to the point where I need to call UEFI's ExitBootServices. Doing so causes the display to turn off and the machine to reset after a few seconds. It doesn't seem to cause any fault that I'm able to catch with exception handlers.

I've tried restoring additional machine state like other control registers and MSRs, VT-d settings, and using the DPR instead of PMRs but none of these seem to affect the behavior.

The processor is an Intel Core i5-8365U. The TXT device ID is 0x1B0088086 and I'm using the SINIT module loaded by the BIOS.

[AndrewG_Intel]

Hello @agold

Thank you for posting on the Intel® communities.

After checking this thread we noticed it seems to be related to Software Development so our recommendation is to review the Intel® Trusted Execution Technology (Intel® TXT) enabling guide:

https://software.intel.com/content/www/us/en/develop/articles/intel-trusted-execution-technology-intel-txt-enabling-guide.html 

If after reviewing the guide you still have questions then please post your inquiry on the Intel Software Development forum and similar ones:

• Software Products Forums >> https://community.intel.com/t5/Software-Products/ct-p/software-products
• Intel® Trusted Execution Technology (Intel® TXT) Forum >> https://community.intel.com/t5/Intel-Trusted-Execution/bd-p/trusted-execution-technology

Having said that, we will proceed to close this inquiry now. If you need any additional information, please submit a new question as this thread will no longer being monitored. Thank you for your understanding.

Best regards,

Andrew G.

Intel Customer Support Technician

[agold]

I've read both the TXT enabling guide and the TXT Software Development Guide but I wasn't able to find a solution to this issue. The SDG doesn't specify how TXT is affected by/affects a UEFI environment.

I'll move this question over to the Software Products board.

Thanks