x86: Secure Launch kernel late boot stub

The routine slaunch_setup() is called out of the x86 specific setup_arch()
routine during early kernel boot. After determining what platform is
present, various operations specific to that platform occur. This
includes finalizing setting for the platform late launch and verifying
that memory protections are in place.

Intel VT-d/IOMMU hardware provides special registers called Protected
Memory Regions (PMRs) that allow all memory to be protected from
DMA during a TXT DRTM launch. This coverage is validated during the
late setup process to ensure DMA protection is in place prior to
the IOMMUs being initialized and configured by the mainline kernel.
See the Intel Trusted Execution Technology - Measured Launch Environment
Developer's Guide for more details:

https://www.intel.com/content/dam/www/public/us/en/documents/guides/intel-txt-software-development-guide.pdf

In addition this routine reserves key memory regions used by Secure Launch
(e.g. the TXT heap, AP startup block etc) as well as fetching values needed
later from the TXT heap and SLRT.

Signed-off-by: Daniel P. Smith <dpsmith@apertussolutions.com>
Signed-off-by: Ross Philipson <ross.philipson@oracle.com>

Author: rossphilipson

arch/x86/kernel/Makefile

@@ -82,6 +82,7 @@ obj-$(CONFIG_X86_32)		+= tls.o
 obj-$(CONFIG_IA32_EMULATION)	+= tls.o
 obj-y				+= step.o
 obj-$(CONFIG_INTEL_TXT)		+= tboot.o
+obj-$(CONFIG_SECURE_LAUNCH)	+= slaunch.o
 obj-$(CONFIG_ISA_DMA_API)	+= i8237.o
 obj-y				+= stacktrace.o
 obj-y				+= cpu/

arch/x86/kernel/setup.c

@@ -24,6 +24,7 @@
 #include <linux/static_call.h>
 #include <linux/swiotlb.h>
 #include <linux/tboot.h>
+#include <linux/slaunch.h>
 #include <linux/usb/xhci-dbgp.h>
 #include <linux/vmalloc.h>
 
@@ -1025,6 +1026,8 @@ void __init setup_arch(char **cmdline_p)
 	early_gart_iommu_check();
 #endif
 
+	slaunch_setup();
+
 	/*
 	 * partially used pages are not usable - thus
 	 * we are rounding upwards: