tools/objtool: Check for use of the ENQCMD instruction in the kernel

mainline inclusion
from mainline-v5.18
commit 6e3133d9
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I596WO


CVE: NA

Intel-SIG: commit 6e3133d9 tools/objtool: Check for use of the ENQCMD instruction in the kernel.
Incremental backporting patches for DSA/IAA on Intel Xeon platform.

--------------------------------

The ENQCMD instruction implicitly accesses the PASID_MSR to fill in the
pasid field of the descriptor being submitted to an accelerator. But
there is no precise (and stable across kernel changes) point at which
the PASID_MSR is updated from the value for one task to the next.

Kernel code that uses accelerators must always use the ENQCMDS instruction
which does not access the PASID_MSR.

Check for use of the ENQCMD instruction in the kernel and warn on its
usage.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Xiaochen Shen <xiaochen.shen@intel.com>