[PATCHv3,12/17] x86/mm: Allow to disable MKTME after enumeration

Commit Message

[e-mail] June 12, 2018, 2:39 p.m. UTC

Separate MKTME enumaration from enabling. We need to postpone enabling
until initialization is complete.

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

Signed-off-by: Kirill A. Shutemov <[e-mail]>
---
 arch/x86/include/asm/mktme.h | 12 ++++++++++++
 arch/x86/kernel/cpu/intel.c  | 15 ++++-----------
 arch/x86/mm/mktme.c          |  9 +++++++++
 3 files changed, 25 insertions(+), 11 deletions(-)

Comments

Dave Hansen June 13, 2018, 6:30 p.m. UTC | #1

On 06/12/2018 07:39 AM, Kirill A. Shutemov wrote:
> Separate MKTME enumaration from enabling. We need to postpone enabling
> until initialization is complete.

	         ^ enumeration

> The new helper mktme_disable() allows to disable MKTME even if it's

s/to disable/disabling/

> enumerated successfully. MKTME initialization may fail and this
> functionallity allows system to boot regardless of the failure.

What can make it fail?

[e-mail] June 18, 2018, 10:59 a.m. UTC | #2

On Wed, Jun 13, 2018 at 06:30:02PM +0000, Dave Hansen wrote:
> On 06/12/2018 07:39 AM, Kirill A. Shutemov wrote:
> > Separate MKTME enumaration from enabling. We need to postpone enabling
> > until initialization is complete.
> 
> 	         ^ enumeration

Nope.

I want to differentiate enumeration in detect_tme() and the point where
MKTME is usable: after mktme_init().

> > The new helper mktme_disable() allows to disable MKTME even if it's
> 
> s/to disable/disabling/

> > enumerated successfully. MKTME initialization may fail and this
> > functionallity allows system to boot regardless of the failure.
> 
> What can make it fail?

I'll add this to commit message:

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.

Patch

diff --git a/arch/x86/include/asm/mktme.h b/arch/x86/include/asm/mktme.h
index ec7036abdb3f..9363b989a021 100644
--- a/arch/x86/include/asm/mktme.h
+++ b/arch/x86/include/asm/mktme.h
@@ -6,11 +6,21 @@ 
 
 struct vm_area_struct;
 
+/* Values for mktme_status */
+#define MKTME_DISABLED			0
+#define MKTME_ENUMERATED		1
+#define MKTME_ENABLED			2
+#define MKTME_UNINITIALIZED		3
+
+extern int mktme_status;
+
 #ifdef CONFIG_X86_INTEL_MKTME
 extern phys_addr_t mktme_keyid_mask;
 extern int mktme_nr_keyids;
 extern int mktme_keyid_shift;
 
+void mktme_disable(void);
+
 #define prep_encrypted_page prep_encrypted_page
 void prep_encrypted_page(struct page *page, int order, int keyid, bool zero);
 
@@ -28,6 +38,8 @@  extern struct page_ext_operations page_mktme_ops;
 #define page_keyid page_keyid
 int page_keyid(const struct page *page);
 
+void mktme_disable(void);
+
 #else
 #define mktme_keyid_mask	((phys_addr_t)0)
 #define mktme_nr_keyids		0
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index efc9e9fc47d4..fb58776513e6 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -508,11 +508,7 @@  static void detect_vmx_virtcap(struct cpuinfo_x86 *c)
 #define TME_ACTIVATE_CRYPTO_ALGS(x)	((x >> 48) & 0xffff)	/* Bits 63:48 */
 #define TME_ACTIVATE_CRYPTO_AES_XTS_128	1
 
-/* Values for mktme_status (SW only construct) */
-#define MKTME_ENABLED			0
-#define MKTME_DISABLED			1
-#define MKTME_UNINITIALIZED		2
-static int mktme_status = MKTME_UNINITIALIZED;
+int mktme_status __ro_after_init = MKTME_UNINITIALIZED;
 
 static void detect_tme(struct cpuinfo_x86 *c)
 {
@@ -568,11 +564,11 @@  static void detect_tme(struct cpuinfo_x86 *c)
 
 	if (mktme_status == MKTME_UNINITIALIZED) {
 		/* MKTME is usable */
-		mktme_status = MKTME_ENABLED;
+		mktme_status = MKTME_ENUMERATED;
 	}
 
 #ifdef CONFIG_X86_INTEL_MKTME
-	if (mktme_status == MKTME_ENABLED && nr_keyids) {
+	if (mktme_status == MKTME_ENUMERATED && nr_keyids) {
 		mktme_nr_keyids = nr_keyids;
 		mktme_keyid_shift = c->x86_phys_bits - keyid_bits;
 
@@ -591,10 +587,7 @@  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 1821b87abb2f..43a44f0f2a2d 100644
--- a/arch/x86/mm/mktme.c
+++ b/arch/x86/mm/mktme.c
@@ -6,6 +6,15 @@  phys_addr_t mktme_keyid_mask;
 int mktme_nr_keyids;
 int mktme_keyid_shift;
 
+void mktme_disable(void)
+{
+	physical_mask = (1ULL << __PHYSICAL_MASK_SHIFT) - 1;
+	mktme_keyid_mask = 0;
+	mktme_keyid_shift = 0;
+	mktme_nr_keyids = 0;
+	mktme_status = MKTME_DISABLED;
+}
+
 int page_keyid(const struct page *page)
 {
 	if (mktme_status != MKTME_ENABLED)