[PATCHv2 12/59] x86/mm: Add a helper to retrieve KeyID for a page

Kirill A. Shutemov
2019-07-31T15:09:47Z

page_ext allows to store additional per-page information without growing
main struct page. The additional space can be requested at boot time.

Store KeyID in bits 31:16 of extended page flags. These bits are unused.

page_keyid() returns zero until page_ext is ready. page_ext initializer
enables a static branch to indicate that page_keyid() can use page_ext.
The same static branch will gate MKTME readiness in general.

We don't yet set KeyID for the page. It will come in the following
patch that implements prep_encrypted_page(). All pages have KeyID-0 for
now.

page_keyid() will be used by KVM which can be built as a module. We need
to export mktme_enabled_key to be able to inline page_keyid().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
arch/x86/include/asm/mktme.h | 26 ++++++++++++++++++++++++++
arch/x86/include/asm/page.h | 1 +
arch/x86/mm/mktme.c | 21 +++++++++++++++++++++
include/linux/mm.h | 2 +-
include/linux/page_ext.h | 11 ++++++++++-
mm/page_ext.c | 3 +++
6 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/mktme.h b/arch/x86/include/asm/mktme.h
index 42a3b1b44669..46041075f617 100644
--- a/arch/x86/include/asm/mktme.h
+++ b/arch/x86/include/asm/mktme.h
@@ -2,6 +2,8 @@
#define _ASM_X86_MKTME_H

#include <linux/types.h>
+#include <linux/page_ext.h>
+#include <linux/jump_label.h>

#ifdef CONFIG_X86_INTEL_MKTME
extern phys_addr_t __mktme_keyid_mask;
@@ -12,10 +14,34 @@ extern int __mktme_nr_keyids;
extern int mktme_nr_keyids(void);
extern unsigned int mktme_algs;

+DECLARE_STATIC_KEY_FALSE(mktme_enabled_key);
+static inline bool mktme_enabled(void)
+{
+ return static_branch_unlikely(&mktme_enabled_key);
+}
+
+extern struct page_ext_operations page_mktme_ops;
+
+#define page_keyid page_keyid
+static inline int page_keyid(const struct page *page)
+{
+ if (!mktme_enabled())
+ return 0;
+
+ return lookup_page_ext(page)->keyid;
+}
+
#else
#define mktme_keyid_mask() ((phys_addr_t)0)
#define mktme_nr_keyids() 0
#define mktme_keyid_shift() 0
+
+#define page_keyid(page) 0
+
+static inline bool mktme_enabled(void)
+{
+ return false;
+}
#endif

#endif
diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h
index 7555b48803a8..39af59487d5f 100644
--- a/arch/x86/include/asm/page.h
+++ b/arch/x86/include/asm/page.h
@@ -19,6 +19,7 @@
struct page;

#include <linux/range.h>
+#include <asm/mktme.h>
extern struct range pfn_mapped[];
extern int nr_pfn_mapped;

diff --git a/arch/x86/mm/mktme.c b/arch/x86/mm/mktme.c
index 755afc6935b5..48c2d4c97356 100644
--- a/arch/x86/mm/mktme.c
+++ b/arch/x86/mm/mktme.c
@@ -27,3 +27,24 @@ int mktme_nr_keyids(void)
}

unsigned int mktme_algs;
+
+DEFINE_STATIC_KEY_FALSE(mktme_enabled_key);
+EXPORT_SYMBOL_GPL(mktme_enabled_key);
+
+static bool need_page_mktme(void)
+{
+ /* Make sure keyid doesn't collide with extended page flags */
+ BUILD_BUG_ON(__NR_PAGE_EXT_FLAGS > 16);
+
+ return !!mktme_nr_keyids();
+}
+
+static void init_page_mktme(void)
+{
+ static_branch_enable(&mktme_enabled_key);
+}
+
+struct page_ext_operations page_mktme_ops = {
+ .need = need_page_mktme,
+ .init = init_page_mktme,
+};
diff --git a/include/linux/mm.h b/include/linux/mm.h
index af1a56ff6764..3f9640f388ac 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1645,7 +1645,7 @@ static inline int vma_keyid(struct vm_area_struct *vma)
#endif

#ifndef page_keyid
-static inline int page_keyid(struct page *page)
+static inline int page_keyid(const struct page *page)
{
return 0;
}
diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h
index 09592951725c..a9fa95ae9847 100644
--- a/include/linux/page_ext.h
+++ b/include/linux/page_ext.h
@@ -22,6 +22,7 @@ enum page_ext_flags {
PAGE_EXT_YOUNG,
PAGE_EXT_IDLE,
#endif
+ __NR_PAGE_EXT_FLAGS
};

/*
@@ -32,7 +33,15 @@ enum page_ext_flags {
* then the page_ext for pfn always exists.
*/
struct page_ext {
- unsigned long flags;
+ union {
+ unsigned long flags;
+#ifdef CONFIG_X86_INTEL_MKTME
+ struct {
+ unsigned short __pad;
+ unsigned short keyid;
+ };
+#endif
+ };
};

extern void pgdat_page_ext_init(struct pglist_data *pgdat);
diff --git a/mm/page_ext.c b/mm/page_ext.c
index 5f5769c7db3b..c52b77c13cd9 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -65,6 +65,9 @@ static struct page_ext_operations *page_ext_ops[] = {
#if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
&page_idle_ops,
#endif
+#ifdef CONFIG_X86_INTEL_MKTME
+ &page_mktme_ops,
+#endif
};

static unsigned long total_usage;
--
2.21.0