linux-kernel - [PATCHv4 13/18] x86/mm: Allow to disable MKTME after enumeration

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Date:   Tue, 26 Jun 2018 17:22:40 +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>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCHv4 13/18] x86/mm: Allow to disable MKTME after enumeration

The new helper mktme_disable() allows to disable MKTME even if it's
enumerated successfully. MKTME initialization may fail and this
functionality allows system to boot regardless of the failure.

MKTME needs per-KeyID direct mapping. It requires a lot more virtual
address space which may be a problem in 4-level paging mode. If the
system has more physical memory than we can handle with MKTME.
The feature allows to fail MKTME, but boot the system successfully.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/include/asm/mktme.h | 2 ++
 arch/x86/kernel/cpu/intel.c  | 5 +----
 arch/x86/mm/mktme.c          | 9 +++++++++
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/mktme.h b/arch/x86/include/asm/mktme.h
index 44409b8bbaca..ebbee6a0c495 100644
--- a/arch/x86/include/asm/mktme.h
+++ b/arch/x86/include/asm/mktme.h
@@ -6,6 +6,8 @@
 
 struct vm_area_struct;
 
+void mktme_disable(void);
+
 #ifdef CONFIG_X86_INTEL_MKTME
 extern phys_addr_t mktme_keyid_mask;
 extern int mktme_nr_keyids;
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index efc9e9fc47d4..75e3b2602b4a 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -591,10 +591,7 @@ static void detect_tme(struct cpuinfo_x86 *c)
 		 * Maybe needed if there's inconsistent configuation
 		 * between CPUs.
 		 */
-		physical_mask = (1ULL << __PHYSICAL_MASK_SHIFT) - 1;
-		mktme_keyid_mask = 0;
-		mktme_keyid_shift = 0;
-		mktme_nr_keyids = 0;
+		mktme_disable();
 	}
 #endif
 
diff --git a/arch/x86/mm/mktme.c b/arch/x86/mm/mktme.c
index 1194496633ce..bb6210dbcf0e 100644
--- a/arch/x86/mm/mktme.c
+++ b/arch/x86/mm/mktme.c
@@ -13,6 +13,15 @@ static inline bool mktme_enabled(void)
 	return static_branch_unlikely(&mktme_enabled_key);
 }
 
+void mktme_disable(void)
+{
+	physical_mask = (1ULL << __PHYSICAL_MASK_SHIFT) - 1;
+	mktme_keyid_mask = 0;
+	mktme_keyid_shift = 0;
+	mktme_nr_keyids = 0;
+	static_branch_disable(&mktme_enabled_key);
+}
+
 int page_keyid(const struct page *page)
 {
 	if (!mktme_enabled())
-- 
2.18.0