[RFC PATCH 08/47] mm: asi: Add basic infrastructure for global non-sensitive mappings

Junaid Shahid
2022-02-23T05:24:34Z

A pseudo-PGD is added to store global non-sensitive ASI mappings.
Actual ASI PGDs copy entries from this pseudo-PGD during asi_init().

Memory can be mapped as globally non-sensitive by calling asi_map()
with ASI_GLOBAL_NONSENSITIVE.

Page tables allocated for global non-sensitive mappings are never
freed.

Signed-off-by: Junaid Shahid <junaids@google.com>

---
arch/x86/include/asm/asi.h | 12 ++++++++++++
arch/x86/mm/asi.c | 36 +++++++++++++++++++++++++++++++++++-
arch/x86/mm/init_64.c | 26 +++++++++++++++++---------
arch/x86/mm/mm_internal.h | 3 +++
include/asm-generic/asi.h | 5 +++++
mm/init-mm.c | 2 ++
6 files changed, 74 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/asi.h b/arch/x86/include/asm/asi.h
index 521b40d1864b..64c2b4d1dba2 100644
--- a/arch/x86/include/asm/asi.h
+++ b/arch/x86/include/asm/asi.h
@@ -15,6 +15,8 @@
#define ASI_MAX_NUM_ORDER 2
#define ASI_MAX_NUM (1 << ASI_MAX_NUM_ORDER)

+#define ASI_GLOBAL_NONSENSITIVE (&init_mm.asi[0])
+
struct asi_state {
struct asi *curr_asi;
struct asi *target_asi;
@@ -41,6 +43,8 @@ struct asi {

DECLARE_PER_CPU_ALIGNED(struct asi_state, asi_cpu_state);

+extern pgd_t asi_global_nonsensitive_pgd[];
+
void asi_init_mm_state(struct mm_struct *mm);

int asi_register_class(const char *name, uint flags,
@@ -117,6 +121,14 @@ static inline void asi_intr_exit(void)
}
}

+#define INIT_MM_ASI(init_mm) \
+ .asi = { \
+ [0] = { \
+ .pgd = asi_global_nonsensitive_pgd, \
+ .mm = &init_mm \
+ } \
+ },
+
static inline pgd_t *asi_pgd(struct asi *asi)
{
return asi->pgd;
diff --git a/arch/x86/mm/asi.c b/arch/x86/mm/asi.c
index 84d220cbdcfc..d381ae573af9 100644
--- a/arch/x86/mm/asi.c
+++ b/arch/x86/mm/asi.c
@@ -1,11 +1,13 @@
// SPDX-License-Identifier: GPL-2.0

#include <linux/init.h>
+#include <linux/memblock.h>

#include <asm/asi.h>
#include <asm/pgalloc.h>
#include <asm/mmu_context.h>

+#include "mm_internal.h"
#include "../../../mm/internal.h"

#undef pr_fmt
@@ -17,6 +19,8 @@ static DEFINE_SPINLOCK(asi_class_lock);
DEFINE_PER_CPU_ALIGNED(struct asi_state, asi_cpu_state);
EXPORT_PER_CPU_SYMBOL_GPL(asi_cpu_state);

+__aligned(PAGE_SIZE) pgd_t asi_global_nonsensitive_pgd[PTRS_PER_PGD];
+
int asi_register_class(const char *name, uint flags,
const struct asi_hooks *ops)
{
@@ -160,12 +164,17 @@ static void asi_free_pgd_range(struct asi *asi, uint start, uint end)
* Free the page tables allocated for the given ASI instance.
* The caller must ensure that all the mappings have already been cleared
* and appropriate TLB flushes have been issued before calling this function.
+ *
+ * For standard non-sensitive ASI classes, the page tables shared with the
+ * master pseudo-PGD are not freed.
*/
static void asi_free_pgd(struct asi *asi)
{
VM_BUG_ON(asi->mm == &init_mm);

- asi_free_pgd_range(asi, KERNEL_PGD_BOUNDARY, PTRS_PER_PGD);
+ if (!(asi->class->flags & ASI_MAP_STANDARD_NONSENSITIVE))
+ asi_free_pgd_range(asi, KERNEL_PGD_BOUNDARY, PTRS_PER_PGD);
+
free_pages((ulong)asi->pgd, PGD_ALLOCATION_ORDER);
}

@@ -178,6 +187,24 @@ static int __init set_asi_param(char *str)
}
early_param("asi", set_asi_param);

+static int __init asi_global_init(void)
+{
+ if (!boot_cpu_has(X86_FEATURE_ASI))
+ return 0;
+
+ preallocate_toplevel_pgtbls(asi_global_nonsensitive_pgd,
+ PAGE_OFFSET,
+ PAGE_OFFSET + PFN_PHYS(max_possible_pfn) - 1,
+ "ASI Global Non-sensitive direct map");
+
+ preallocate_toplevel_pgtbls(asi_global_nonsensitive_pgd,
+ VMALLOC_START, VMALLOC_END,
+ "ASI Global Non-sensitive vmalloc");
+
+ return 0;
+}
+subsys_initcall(asi_global_init)
+
int asi_init(struct mm_struct *mm, int asi_index)
{
struct asi *asi = &mm->asi[asi_index];
@@ -202,6 +229,13 @@ int asi_init(struct mm_struct *mm, int asi_index)
asi->class = &asi_class[asi_index];
asi->mm = mm;

+ if (asi->class->flags & ASI_MAP_STANDARD_NONSENSITIVE) {
+ uint i;
+
+ for (i = KERNEL_PGD_BOUNDARY; i < PTRS_PER_PGD; i++)
+ set_pgd(asi->pgd + i, asi_global_nonsensitive_pgd[i]);
+ }
+
return 0;
}
EXPORT_SYMBOL_GPL(asi_init);
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 36098226a957..ebd512c64ed0 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1277,18 +1277,15 @@ static void __init register_page_bootmem_info(void)
#endif
}

-/*
- * Pre-allocates page-table pages for the vmalloc area in the kernel page-table.
- * Only the level which needs to be synchronized between all page-tables is
- * allocated because the synchronization can be expensive.
- */
-static void __init preallocate_vmalloc_pages(void)
+void __init preallocate_toplevel_pgtbls(pgd_t *pgd_table,
+ ulong start, ulong end,
+ const char *name)
{
unsigned long addr;
const char *lvl;

- for (addr = VMALLOC_START; addr <= VMALLOC_END; addr = ALIGN(addr + 1, PGDIR_SIZE)) {
- pgd_t *pgd = pgd_offset_k(addr);
+ for (addr = start; addr <= end; addr = ALIGN(addr + 1, PGDIR_SIZE)) {
+ pgd_t *pgd = pgd_offset_pgd(pgd_table, addr);
p4d_t *p4d;
pud_t *pud;

@@ -1324,7 +1321,18 @@ static void __init preallocate_vmalloc_pages(void)
* The pages have to be there now or they will be missing in
* process page-tables later.
*/
- panic("Failed to pre-allocate %s pages for vmalloc area\n", lvl);
+ panic("Failed to pre-allocate %s pages for %s area\n", lvl, name);
+}
+
+/*
+ * Pre-allocates page-table pages for the vmalloc area in the kernel page-table.
+ * Only the level which needs to be synchronized between all page-tables is
+ * allocated because the synchronization can be expensive.
+ */
+static void __init preallocate_vmalloc_pages(void)
+{
+ preallocate_toplevel_pgtbls(init_mm.pgd, VMALLOC_START, VMALLOC_END,
+ "vmalloc");
}

void __init mem_init(void)
diff --git a/arch/x86/mm/mm_internal.h b/arch/x86/mm/mm_internal.h
index 3f37b5c80bb3..a1e8c523ab08 100644
--- a/arch/x86/mm/mm_internal.h
+++ b/arch/x86/mm/mm_internal.h
@@ -19,6 +19,9 @@ unsigned long kernel_physical_mapping_change(unsigned long start,
unsigned long page_size_mask);
void zone_sizes_init(void);

+void preallocate_toplevel_pgtbls(pgd_t *pgd_table, ulong start, ulong end,
+ const char *name);
+
extern int after_bootmem;

void update_cache_mode_entry(unsigned entry, enum page_cache_mode cache);
diff --git a/include/asm-generic/asi.h b/include/asm-generic/asi.h
index 7da91cbe075d..012691e29895 100644
--- a/include/asm-generic/asi.h
+++ b/include/asm-generic/asi.h
@@ -12,6 +12,8 @@
#define ASI_MAX_NUM_ORDER 0
#define ASI_MAX_NUM 0

+#define ASI_GLOBAL_NONSENSITIVE NULL
+
#ifndef _ASSEMBLY_

struct asi_hooks {};
@@ -63,8 +65,11 @@ void asi_unmap(struct asi *asi, void *addr, size_t len, bool flush_tlb) { }
static inline
void asi_flush_tlb_range(struct asi *asi, void *addr, size_t len) { }

+#define INIT_MM_ASI(init_mm)
+
#define static_asi_enabled() false

+
#endif /* !_ASSEMBLY_ */

#endif /* !CONFIG_ADDRESS_SPACE_ISOLATION */
diff --git a/mm/init-mm.c b/mm/init-mm.c
index b4a6f38fb51d..47a6a66610fb 100644
--- a/mm/init-mm.c
+++ b/mm/init-mm.c
@@ -11,6 +11,7 @@
#include <linux/atomic.h>
#include <linux/user_namespace.h>
#include <asm/mmu.h>
+#include <asm/asi.h>

#ifndef INIT_MM_CONTEXT
#define INIT_MM_CONTEXT(name)
@@ -38,6 +39,7 @@ struct mm_struct init_mm = {
.mmlist = LIST_HEAD_INIT(init_mm.mmlist),
.user_ns = &init_user_ns,
.cpu_bitmap = CPU_BITS_NONE,
+ INIT_MM_ASI(init_mm)
INIT_MM_CONTEXT(init_mm)
};

--
2.35.1.473.g83b2b277ed-goog