linux-kernel - [PATCH 1/2] x86/mm: Fix comment in detect_tme() regarding x86_phys

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Date:   Thu, 15 Mar 2018 16:49:06 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 1/2] x86/mm: Fix comment in detect_tme() regarding x86_phys_bits

As Kai pointed, we adjust x86_phys_bits not only to communicate
available physical address space to virtual machines, but mainly to
reflect the fact that the address space is reduced.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Suggested-by: Kai Huang <kai.huang@...ux.intel.com>
---
 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 f0481b85c39d..fd379358c58d 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -619,11 +619,8 @@ static void detect_tme(struct cpuinfo_x86 *c)
 #endif
 
 	/*
-	 * 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 number of physical address bits.
+	 * Let's update cpuinfo_x86::x86_phys_bits to reflect the fact.
 	 */
 	c->x86_phys_bits -= keyid_bits;
 }
-- 
2.16.1