PCID Bit Flag CR4 - Need Someone to Test on a Intel CPU

x BlueRobot · Dec 19, 2013

I'm currently writing another blog post about the TLB, and came across a Intel instruction for invalidating specific TLB entries based upon the current PCID (Process Context Identifier) if the bit was enabled in the CR4 register. I've read that PCID is supported by Intel, but need to check for AMD.

Here's my output from WinDbg with a AMD CPU, and the bit doesn't seem to be enabled or isn't supported.

Code:

0: kd> .formats @cr4
Evaluate expression:
  Hex:     000006f9
  Decimal: 1785
  Octal:   00000003371
  Binary:  00000000 00000000 00000110 11111001 <-- 17th Bit
  Chars:   ....
  Time:    Thu Jan 01 00:29:45 1970
  Float:   low 2.50132e-042 high 0
  Double:  8.81907e-321

This command should also work:

Code:

0: kd> j ((@cr4 & 0y00000000000000010000000000000000) != 0)'.echo PCID Flag Enabled';'.echo PCID Flag Disabled'

The current output:

Code:

PCID Flag Disabled

Thanks for any feedback!

Search

Search

PCID Bit Flag CR4 - Need Someone to Test on a Intel CPU

x BlueRobot

Administrator