doc: clarify CS.base restriction for KVM

Clarify that the CS.base restriction is a prescription of
compatibility, and not something that the ABI handles transparently.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

diff --git a/doc/comboot.txt b/doc/comboot.txt
index 68f1e7e..cf18b2b 100644 (file)
--- a/doc/comboot.txt
+++ b/doc/comboot.txt
@@ -948,8 +948,8 @@ AX=0024h [3.80] Cleanup, shuffle and boot, raw version
        For mode 0 (16-bit real mode), EAX will contain CR0 with bit 0
        masked out, suitable for loading into CR0 to immediately enter
        real mode.  Note: if real-mode entry is planned,
-       (CS.base & 0xfff0000f) == 0 for compatibility with KVM, and
-       possibly other virtualization solutions.
+       (CS.base & 0xfff0000f) should == 0 for compatibility with KVM,
+       and possibly other virtualization solutions.
 
        In both mode 0 and mode 1, the data segments will be loaded
        with base-zero read/write segments.  For mode 0, B=0 and the