diff mbox series

[V2,4/4] arm64: mm: introduce 52-bit userspace support

Message ID 20181017163459.20175-5-steve.capper@arm.com (mailing list archive)
State Superseded, archived
Headers show
Series 52-bit userspace VAs | expand

Commit Message

Steve Capper Oct. 17, 2018, 4:34 p.m. UTC 
On arm64 there is optional support for a 52-bit virtual address space.
To exploit this one has to be running with a 64KB page size and be
running on hardware that supports this.

For an arm64 kernel supporting a 48 bit VA with a 64KB page size,
a few changes are needed to support a 52-bit userspace:
 * TCR_EL1.T0SZ needs to be 12 instead of 16,
 * pgd_offset needs to work with a different PTRS_PER_PGD,
 * PGD_SIZE needs to be increased,
 * TASK_SIZE needs to reflect the new size.

This patch implements the above when the support for 52-bit VAs is
detected at early boot time.

On arm64 userspace addresses translation is controlled by TTBR0_EL1. As
well as userspace, TTBR0_EL1 controls:
 * The identity mapping,
 * EFI runtime code.

It is possible to run a kernel with an identity mapping that has a
larger VA size than userspace (and for this case __cpu_set_tcr_t0sz()
would set TCR_EL1.T0SZ as appropriate). However, when the conditions for
52-bit userspace are met; it is possible to keep TCR_EL1.T0SZ fixed at
12. Thus in this patch, the TCR_EL1.T0SZ size changing logic is
disabled.

Signed-off-by: Steve Capper <steve.capper@arm.com>
---
Changed in V2: variable USER_DS limit dropped, this simplifies the
patch considerably. We check for userspace mappings with init_mm rather
than looking at the virtual address.
---
 arch/arm64/Kconfig                   |  4 ++++
 arch/arm64/include/asm/assembler.h   |  7 +++----
 arch/arm64/include/asm/mmu_context.h |  3 +++
 arch/arm64/include/asm/pgalloc.h     |  4 ++++
 arch/arm64/include/asm/pgtable.h     | 16 +++++++++++++---
 arch/arm64/include/asm/processor.h   | 13 ++++++++-----
 arch/arm64/kernel/head.S             | 13 +++++++++++++
 arch/arm64/mm/fault.c                |  2 +-
 arch/arm64/mm/mmu.c                  |  1 +
 arch/arm64/mm/proc.S                 | 10 +++++++++-
 10 files changed, 59 insertions(+), 14 deletions(-)

Comments

kernel test robot Oct. 18, 2018, 2:44 a.m. UTC | #1 
Hi Steve,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on arm64/for-next/core]
[also build test ERROR on v4.19-rc8]
[cannot apply to next-20181017]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Steve-Capper/52-bit-userspace-VAs/20181018-061652
base:   https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core
config: arm64-defconfig (attached as .config)
compiler: aarch64-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.2.0 make.cross ARCH=arm64 

All error/warnings (new ones prefixed by >>):

   In file included from include/linux/export.h:45:0,
                    from include/linux/linkage.h:7,
                    from include/linux/kernel.h:7,
                    from arch/arm64/mm/init.c:20:
   arch/arm64/mm/init.c: In function 'mem_init':
>> include/linux/compiler.h:358:38: error: call to '__compiletime_assert_613' declared with attribute error: BUILD_BUG_ON failed: TASK_SIZE_32 > TASK_SIZE_64
     _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
                                         ^
   include/linux/compiler.h:338:4: note: in definition of macro '__compiletime_assert'
       prefix ## suffix();    \
       ^~~~~~
   include/linux/compiler.h:358:2: note: in expansion of macro '_compiletime_assert'
     _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
     ^~~~~~~~~~~~~~~~~~~
   include/linux/build_bug.h:45:37: note: in expansion of macro 'compiletime_assert'
    #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
                                        ^~~~~~~~~~~~~~~~~~
   include/linux/build_bug.h:69:2: note: in expansion of macro 'BUILD_BUG_ON_MSG'
     BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
     ^~~~~~~~~~~~~~~~
>> arch/arm64/mm/init.c:613:2: note: in expansion of macro 'BUILD_BUG_ON'
     BUILD_BUG_ON(TASK_SIZE_32   > TASK_SIZE_64);
     ^~~~~~~~~~~~

vim +/__compiletime_assert_613 +358 include/linux/compiler.h

9a8ab1c3 Daniel Santos 2013-02-21  344  
9a8ab1c3 Daniel Santos 2013-02-21  345  #define _compiletime_assert(condition, msg, prefix, suffix) \
9a8ab1c3 Daniel Santos 2013-02-21  346  	__compiletime_assert(condition, msg, prefix, suffix)
9a8ab1c3 Daniel Santos 2013-02-21  347  
9a8ab1c3 Daniel Santos 2013-02-21  348  /**
9a8ab1c3 Daniel Santos 2013-02-21  349   * compiletime_assert - break build and emit msg if condition is false
9a8ab1c3 Daniel Santos 2013-02-21  350   * @condition: a compile-time constant condition to check
9a8ab1c3 Daniel Santos 2013-02-21  351   * @msg:       a message to emit if condition is false
9a8ab1c3 Daniel Santos 2013-02-21  352   *
9a8ab1c3 Daniel Santos 2013-02-21  353   * In tradition of POSIX assert, this macro will break the build if the
9a8ab1c3 Daniel Santos 2013-02-21  354   * supplied condition is *false*, emitting the supplied error message if the
9a8ab1c3 Daniel Santos 2013-02-21  355   * compiler has support to do so.
9a8ab1c3 Daniel Santos 2013-02-21  356   */
9a8ab1c3 Daniel Santos 2013-02-21  357  #define compiletime_assert(condition, msg) \
9a8ab1c3 Daniel Santos 2013-02-21 @358  	_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
9a8ab1c3 Daniel Santos 2013-02-21  359  

:::::: The code at line 358 was first introduced by commit
:::::: 9a8ab1c39970a4938a72d94e6fd13be88a797590 bug.h, compiler.h: introduce compiletime_assert & BUILD_BUG_ON_MSG

:::::: TO: Daniel Santos <daniel.santos@pobox.com>
:::::: CC: Linus Torvalds <torvalds@linux-foundation.org>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
diff mbox series

Patch

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1b1a0e95c751..ce6ebba101de 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -691,6 +691,10 @@  config ARM64_PA_BITS_52
 
 endchoice
 
+config ARM64_52BIT_VA
+	def_bool y
+	depends on ARM64_VA_BITS_48 && ARM64_64K_PAGES
+
 config ARM64_PA_BITS
 	int
 	default 48 if ARM64_PA_BITS_48
diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 0bcc98dbba56..8c8ed20beca9 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -343,11 +343,10 @@  alternative_endif
 	.endm
 
 /*
- * tcr_set_idmap_t0sz - update TCR.T0SZ so that we can load the ID map
+ * tcr_set_t0sz - update TCR.T0SZ so that we can load the ID map
  */
-	.macro	tcr_set_idmap_t0sz, valreg, tmpreg
-	ldr_l	\tmpreg, idmap_t0sz
-	bfi	\valreg, \tmpreg, #TCR_T0SZ_OFFSET, #TCR_TxSZ_WIDTH
+	.macro	tcr_set_t0sz, valreg, t0sz
+	bfi	\valreg, \t0sz, #TCR_T0SZ_OFFSET, #TCR_TxSZ_WIDTH
 	.endm
 
 /*
diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index 39ec0b8a689e..1b7408e8d794 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -72,6 +72,9 @@  extern u64 idmap_ptrs_per_pgd;
 
 static inline bool __cpu_uses_extended_idmap(void)
 {
+	if (IS_ENABLED(CONFIG_ARM64_52BIT_VA))
+		return false;
+
 	return unlikely(idmap_t0sz != TCR_T0SZ(VA_BITS));
 }
 
diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h
index 2e05bcd944c8..56c3ccabeffe 100644
--- a/arch/arm64/include/asm/pgalloc.h
+++ b/arch/arm64/include/asm/pgalloc.h
@@ -27,7 +27,11 @@ 
 #define check_pgt_cache()		do { } while (0)
 
 #define PGALLOC_GFP	(GFP_KERNEL | __GFP_ZERO)
+#ifdef CONFIG_ARM64_52BIT_VA
+#define PGD_SIZE	((1 << (52 - PGDIR_SHIFT)) * sizeof(pgd_t))
+#else
 #define PGD_SIZE	(PTRS_PER_PGD * sizeof(pgd_t))
+#endif
 
 #if CONFIG_PGTABLE_LEVELS > 2
 
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 1bdeca8918a6..b18df27b06e0 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -577,11 +577,21 @@  static inline phys_addr_t pgd_page_paddr(pgd_t pgd)
 #define pgd_ERROR(pgd)		__pgd_error(__FILE__, __LINE__, pgd_val(pgd))
 
 /* to find an entry in a page-table-directory */
-#define pgd_index(addr)		(((addr) >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1))
+#define pgd_index(addr, ptrs)		(((addr) >> PGDIR_SHIFT) & ((ptrs) - 1))
+#define _pgd_offset_raw(pgd, addr, ptrs) ((pgd) + pgd_index(addr, ptrs))
+#define pgd_offset_raw(pgd, addr)	(_pgd_offset_raw(pgd, addr, PTRS_PER_PGD))
 
-#define pgd_offset_raw(pgd, addr)	((pgd) + pgd_index(addr))
+static inline pgd_t *pgd_offset(const struct mm_struct *mm, unsigned long addr)
+{
+	pgd_t *ret;
+
+	if (IS_ENABLED(CONFIG_ARM64_52BIT_VA) && (mm != &init_mm))
+		ret = _pgd_offset_raw(mm->pgd, addr, 1ULL << (vabits_user - PGDIR_SHIFT));
+	else
+		ret = pgd_offset_raw(mm->pgd, addr);
 
-#define pgd_offset(mm, addr)	(pgd_offset_raw((mm)->pgd, (addr)))
+	return ret;
+}
 
 /* to find an entry in a kernel page-table-directory */
 #define pgd_offset_k(addr)	pgd_offset(&init_mm, addr)
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 5afc0c5eb1cb..886392ac38ff 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -19,13 +19,16 @@ 
 #ifndef __ASM_PROCESSOR_H
 #define __ASM_PROCESSOR_H
 
-#define TASK_SIZE_64		(UL(1) << VA_BITS)
-
-#define KERNEL_DS	UL(-1)
-#define USER_DS		(TASK_SIZE_64 - 1)
-
+#define KERNEL_DS		UL(-1)
+#ifdef CONFIG_ARM64_52BIT_VA
+#define USER_DS			((UL(1) << 52) - 1)
+#else
+#define USER_DS			((UL(1) << VA_BITS) - 1)
+#endif /* CONFIG_ARM64_52IT_VA */
 #ifndef __ASSEMBLY__
 
+extern u64 vabits_user;
+#define TASK_SIZE_64		(UL(1) << vabits_user)
 #define DEFAULT_MAP_WINDOW_64	(UL(1) << VA_BITS)
 
 /*
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index b0853069702f..796d119f2848 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -316,6 +316,19 @@  __create_page_tables:
 	adrp	x0, idmap_pg_dir
 	adrp	x3, __idmap_text_start		// __pa(__idmap_text_start)
 
+#ifdef CONFIG_ARM64_52BIT_VA
+	mrs_s	x6, SYS_ID_AA64MMFR2_EL1
+	and	x6, x6, #(0xf << ID_AA64MMFR2_LVA_SHIFT)
+	mov	x5, #52
+	cbnz	x6, 1f
+#endif
+	mov	x5, #VA_BITS
+1:
+	adr_l	x6, vabits_user
+	str	x5, [x6]
+	dmb	sy
+	dc	ivac, x6		// Invalidate potentially stale cache line
+
 	/*
 	 * VA_BITS may be too small to allow for an ID mapping to be created
 	 * that covers system RAM if that is located sufficiently high in the
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 50b30ff30de4..cbf14bc14aa3 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -153,7 +153,7 @@  void show_pte(unsigned long addr)
 
 	pr_alert("%s pgtable: %luk pages, %u-bit VAs, pgdp = %p\n",
 		 mm == &init_mm ? "swapper" : "user", PAGE_SIZE / SZ_1K,
-		 VA_BITS, mm->pgd);
+		 mm == &init_mm ? VA_BITS : (int) vabits_user, mm->pgd);
 	pgdp = pgd_offset(mm, addr);
 	pgd = READ_ONCE(*pgdp);
 	pr_alert("[%016lx] pgd=%016llx", addr, pgd_val(pgd));
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 8080c9f489c3..2aa9ea9bd2c2 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -52,6 +52,7 @@ 
 
 u64 idmap_t0sz = TCR_T0SZ(VA_BITS);
 u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
+u64 vabits_user __ro_after_init;
 
 u64 kimage_voffset __ro_after_init;
 EXPORT_SYMBOL(kimage_voffset);
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 03646e6a2ef4..bd01506a2555 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -441,7 +441,15 @@  ENTRY(__cpu_setup)
 	ldr	x10, =TCR_TxSZ(VA_BITS) | TCR_CACHE_FLAGS | TCR_SMP_FLAGS | \
 			TCR_TG_FLAGS | TCR_KASLR_FLAGS | TCR_ASID16 | \
 			TCR_TBI0 | TCR_A1
-	tcr_set_idmap_t0sz	x10, x9
+
+#ifdef CONFIG_ARM64_52BIT_VA
+	ldr_l 		x9, vabits_user
+	sub		x9, xzr, x9
+	add		x9, x9, #64
+#else
+	ldr_l		x9, idmap_t0sz
+#endif
+	tcr_set_t0sz	x10, x9
 
 	/*
 	 * Set the IPS bits in TCR_EL1.