[tip:x86/mm] x86/mm: Update comment in detect_tme() regarding x86_phys_bits

[tip-bot for Kirill A. Shutemov]

Commit-ID:  547edaca247abf910e32f0cd883ba83b8fc6d0ed
Gitweb:     https://git.kernel.org/tip/547edaca247abf910e32f0cd883ba83b8fc6d0ed
Author:     Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
AuthorDate: Thu, 15 Mar 2018 16:49:06 +0300
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Tue, 27 Mar 2018 11:49:58 +0200

x86/mm: Update comment in detect_tme() regarding x86_phys_bits

As Kai pointed out, the primary reason for adjusting x86_phys_bits is to
reflect that the the address space is reduced and not the ability to
communicate the available physical address space to virtual machines.

Suggested-by: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Link: https://lkml.kernel.org/r/20180315134907.9311-2-kirill.shutemov@xxxxxxxxxxxxxxx

---
 arch/x86/kernel/cpu/intel.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 3f8d7a3b6447..6106d11ceb6b 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -587,11 +587,8 @@ detect_keyid_bits:
 	}
 
 	/*
-	 * Exclude KeyID bits from physical address bits.
-	 *
-	 * We have to do this even if we are not going to use KeyID bits
-	 * ourself. VM guests still have to know that these bits are not usable
-	 * for physical address.
+	 * KeyID bits effectively lower the number of physical address
+	 * bits.  Update cpuinfo_x86::x86_phys_bits accordingly.
 	 */
 	c->x86_phys_bits -= keyid_bits;
 }