linux-kernel - [RFC PATCH v4 04/28] x86: Handle reduction in physical address size with SME

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Date:   Thu, 16 Feb 2017 09:42:54 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     <linux-arch@...r.kernel.org>, <linux-efi@...r.kernel.org>,
        <kvm@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
        <kasan-dev@...glegroups.com>, <linux-mm@...ck.org>,
        <iommu@...ts.linux-foundation.org>
CC:     Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Larry Woodman <lwoodman@...hat.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: [RFC PATCH v4 04/28] x86: Handle reduction in physical address size
 with SME

When System Memory Encryption (SME) is enabled, the physical address
space is reduced. Adjust the x86_phys_bits value to reflect this
reduction.

Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
---
 arch/x86/kernel/cpu/common.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index b33bc06..358208d7 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -771,11 +771,15 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
 			u64 msr;
 
 			/*
-			 * For SME, BIOS support is required. If BIOS has not
-			 * enabled SME don't advertise the feature.
+			 * For SME, BIOS support is required. If BIOS has
+			 * enabled SME adjust x86_phys_bits by the SME
+			 * physical address space reduction value. If BIOS
+			 * has not enabled SME don't advertise the feature.
 			 */
 			rdmsrl(MSR_K8_SYSCFG, msr);
-			if (!(msr & MSR_K8_SYSCFG_MEM_ENCRYPT))
+			if (msr & MSR_K8_SYSCFG_MEM_ENCRYPT)
+				c->x86_phys_bits -= (ebx >> 6) & 0x3f;
+			else
 				eax &= ~0x01;
 		}