On riscv, mmap currently returns an address from the largest address
space that can fit entirely inside of the hint address. This makes it
such that the hint address is almost never returned. This patch raises
the mappable area up to and including the hint address. This allows mmap
to often return the hint address, which allows a performance improvement
over searching for a valid address as well as making the behavior more
similar to other architectures.
Note that a previous patch introduced stronger semantics compared to
other architectures for riscv mmap. On riscv, mmap will not use bits in
the upper bits of the virtual address depending on the hint address. On
other architectures, a random address is returned in the address space
requested. On all architectures the hint address will be returned if it
is available. This allows riscv applications to configure how many bits
in the virtual address should be left empty. This has the two benefits
of being able to request address spaces that are smaller than the
default and doesn't require the application to know the page table
layout of riscv.
Signed-off-by: Charlie Jenkins <[email protected]>
---
Changes in v3:
- Add back forgotten semi-colon
- Fix test cases
- Add support for rv32
- Change cover letter name so it's not the same as patch 1
- Link to v2: https://lore.kernel.org/r/[email protected]
Changes in v2:
- Add back forgotten "mmap_end = STACK_TOP_MAX"
- Link to v1: https://lore.kernel.org/r/[email protected]
---
Charlie Jenkins (3):
riscv: mm: Use hint address in mmap if available
selftests: riscv: Generalize mm selftests
docs: riscv: Define behavior of mmap
Documentation/arch/riscv/vm-layout.rst | 16 ++--
arch/riscv/include/asm/processor.h | 27 +++---
tools/testing/selftests/riscv/mm/mmap_bottomup.c | 23 +----
tools/testing/selftests/riscv/mm/mmap_default.c | 23 +----
tools/testing/selftests/riscv/mm/mmap_test.h | 107 ++++++++++++++---------
5 files changed, 83 insertions(+), 113 deletions(-)
---
base-commit: 556e2d17cae620d549c5474b1ece053430cd50bc
change-id: 20240119-use_mmap_hint_address-f9f4b1b6f5f1
--
- Charlie
The behavior of mmap on riscv is defined to not provide an address that
uses more bits than the hint address, if provided. Make the tests
reflect that.
Signed-off-by: Charlie Jenkins <[email protected]>
---
tools/testing/selftests/riscv/mm/mmap_bottomup.c | 23 +----
tools/testing/selftests/riscv/mm/mmap_default.c | 23 +----
tools/testing/selftests/riscv/mm/mmap_test.h | 107 ++++++++++++++---------
3 files changed, 67 insertions(+), 86 deletions(-)
diff --git a/tools/testing/selftests/riscv/mm/mmap_bottomup.c b/tools/testing/selftests/riscv/mm/mmap_bottomup.c
index 1757d19ca89b..7f7d3eb8b9c9 100644
--- a/tools/testing/selftests/riscv/mm/mmap_bottomup.c
+++ b/tools/testing/selftests/riscv/mm/mmap_bottomup.c
@@ -6,30 +6,9 @@
TEST(infinite_rlimit)
{
-// Only works on 64 bit
-#if __riscv_xlen == 64
- struct addresses mmap_addresses;
-
EXPECT_EQ(BOTTOM_UP, memory_layout());
- do_mmaps(&mmap_addresses);
-
- EXPECT_NE(MAP_FAILED, mmap_addresses.no_hint);
- EXPECT_NE(MAP_FAILED, mmap_addresses.on_37_addr);
- EXPECT_NE(MAP_FAILED, mmap_addresses.on_38_addr);
- EXPECT_NE(MAP_FAILED, mmap_addresses.on_46_addr);
- EXPECT_NE(MAP_FAILED, mmap_addresses.on_47_addr);
- EXPECT_NE(MAP_FAILED, mmap_addresses.on_55_addr);
- EXPECT_NE(MAP_FAILED, mmap_addresses.on_56_addr);
-
- EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.no_hint);
- EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_37_addr);
- EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_38_addr);
- EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_46_addr);
- EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.on_47_addr);
- EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.on_55_addr);
- EXPECT_GT(1UL << 56, (unsigned long)mmap_addresses.on_56_addr);
-#endif
+ TEST_MMAPS;
}
TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/riscv/mm/mmap_default.c b/tools/testing/selftests/riscv/mm/mmap_default.c
index c63c60b9397e..2ba3ec990006 100644
--- a/tools/testing/selftests/riscv/mm/mmap_default.c
+++ b/tools/testing/selftests/riscv/mm/mmap_default.c
@@ -6,30 +6,9 @@
TEST(default_rlimit)
{
-// Only works on 64 bit
-#if __riscv_xlen == 64
- struct addresses mmap_addresses;
-
EXPECT_EQ(TOP_DOWN, memory_layout());
- do_mmaps(&mmap_addresses);
-
- EXPECT_NE(MAP_FAILED, mmap_addresses.no_hint);
- EXPECT_NE(MAP_FAILED, mmap_addresses.on_37_addr);
- EXPECT_NE(MAP_FAILED, mmap_addresses.on_38_addr);
- EXPECT_NE(MAP_FAILED, mmap_addresses.on_46_addr);
- EXPECT_NE(MAP_FAILED, mmap_addresses.on_47_addr);
- EXPECT_NE(MAP_FAILED, mmap_addresses.on_55_addr);
- EXPECT_NE(MAP_FAILED, mmap_addresses.on_56_addr);
-
- EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.no_hint);
- EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_37_addr);
- EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_38_addr);
- EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_46_addr);
- EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.on_47_addr);
- EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.on_55_addr);
- EXPECT_GT(1UL << 56, (unsigned long)mmap_addresses.on_56_addr);
-#endif
+ TEST_MMAPS;
}
TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/riscv/mm/mmap_test.h b/tools/testing/selftests/riscv/mm/mmap_test.h
index 9b8434f62f57..36e78d991d5e 100644
--- a/tools/testing/selftests/riscv/mm/mmap_test.h
+++ b/tools/testing/selftests/riscv/mm/mmap_test.h
@@ -4,60 +4,83 @@
#include <sys/mman.h>
#include <sys/resource.h>
#include <stddef.h>
+#include <strings.h>
+#include "../../kselftest_harness.h"
#define TOP_DOWN 0
#define BOTTOM_UP 1
-struct addresses {
- int *no_hint;
- int *on_37_addr;
- int *on_38_addr;
- int *on_46_addr;
- int *on_47_addr;
- int *on_55_addr;
- int *on_56_addr;
+#if __riscv_xlen == 64
+uint64_t random_addresses[] = {
+ 0x19764f0d73b3a9f0, 0x016049584cecef59, 0x3580bdd3562f4acd,
+ 0x1164219f20b17da0, 0x07d97fcb40ff2373, 0x76ec528921272ee7,
+ 0x4dd48c38a3de3f70, 0x2e11415055f6997d, 0x14b43334ac476c02,
+ 0x375a60795aff19f6, 0x47f3051725b8ee1a, 0x4e697cf240494a9f,
+ 0x456b59b5c2f9e9d1, 0x101724379d63cb96, 0x7fe9ad31619528c1,
+ 0x2f417247c495c2ea, 0x329a5a5b82943a5e, 0x06d7a9d6adcd3827,
+ 0x327b0b9ee37f62d5, 0x17c7b1851dfd9b76, 0x006ebb6456ec2cd9,
+ 0x00836cd14146a134, 0x00e5c4dcde7126db, 0x004c29feadf75753,
+ 0x00d8b20149ed930c, 0x00d71574c269387a, 0x0006ebe4a82acb7a,
+ 0x0016135df51f471b, 0x00758bdb55455160, 0x00d0bdd949b13b32,
+ 0x00ecea01e7c5f54b, 0x00e37b071b9948b1, 0x0011fdd00ff57ab3,
+ 0x00e407294b52f5ea, 0x00567748c200ed20, 0x000d073084651046,
+ 0x00ac896f4365463c, 0x00eb0d49a0b26216, 0x0066a2564a982a31,
+ 0x002e0d20237784ae, 0x0000554ff8a77a76, 0x00006ce07a54c012,
+ 0x000009570516d799, 0x00000954ca15b84d, 0x0000684f0d453379,
+ 0x00002ae5816302b5, 0x0000042403fb54bf, 0x00004bad7392bf30,
+ 0x00003e73bfa4b5e3, 0x00005442c29978e0, 0x00002803f11286b6,
+ 0x000073875d745fc6, 0x00007cede9cb8240, 0x000027df84cc6a4f,
+ 0x00006d7e0e74242a, 0x00004afd0b836e02, 0x000047d0e837cd82,
+ 0x00003b42405efeda, 0x00001531bafa4c95, 0x00007172cae34ac4,
};
+#else
+uint32_t random_addresses[] = {
+ 0x8dc302e0, 0x929ab1e0, 0xb47683ba, 0xea519c73, 0xa19f1c90, 0xc49ba213,
+ 0x8f57c625, 0xadfe5137, 0x874d4d95, 0xaa20f09d, 0xcf21ebfc, 0xda7737f1,
+ 0xcedf392a, 0x83026c14, 0xccedca52, 0xc6ccf826, 0xe0cd9415, 0x997472ca,
+ 0xa21a44c1, 0xe82196f5, 0xa23fd66b, 0xc28d5590, 0xd009cdce, 0xcf0be646,
+ 0x8fc8c7ff, 0xe2a85984, 0xa3d3236b, 0x89a0619d, 0xc03db924, 0xb5d4cc1b,
+ 0xb96ee04c, 0xd191da48, 0xb432a000, 0xaa2bebbc, 0xa2fcb289, 0xb0cca89b,
+ 0xb0c18d6a, 0x88f58deb, 0xa4d42d1c, 0xe4d74e86, 0x99902b09, 0x8f786d31,
+ 0xbec5e381, 0x9a727e65, 0xa9a65040, 0xa880d789, 0x8f1b335e, 0xfc821c1e,
+ 0x97e34be4, 0xbbef84ed, 0xf447d197, 0xfd7ceee2, 0xe632348d, 0xee4590f4,
+ 0x958992a5, 0xd57e05d6, 0xfd240970, 0xc5b0dcff, 0xd96da2c2, 0xa7ae041d,
+};
+#endif
-static inline void do_mmaps(struct addresses *mmap_addresses)
-{
- /*
- * Place all of the hint addresses on the boundaries of mmap
- * sv39, sv48, sv57
- * User addresses end at 1<<38, 1<<47, 1<<56 respectively
- */
- void *on_37_bits = (void *)(1UL << 37);
- void *on_38_bits = (void *)(1UL << 38);
- void *on_46_bits = (void *)(1UL << 46);
- void *on_47_bits = (void *)(1UL << 47);
- void *on_55_bits = (void *)(1UL << 55);
- void *on_56_bits = (void *)(1UL << 56);
+#define PROT (PROT_READ | PROT_WRITE)
+#define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS)
- int prot = PROT_READ | PROT_WRITE;
- int flags = MAP_PRIVATE | MAP_ANONYMOUS;
+/* mmap must return a value that doesn't use more bits than the hint address. */
+static inline unsigned long get_max_value(unsigned long input)
+{
+ unsigned long max_bit = (1UL << (((sizeof(unsigned long) * 8) - 1 -
+ __builtin_clzl(input))));
- mmap_addresses->no_hint =
- mmap(NULL, 5 * sizeof(int), prot, flags, 0, 0);
- mmap_addresses->on_37_addr =
- mmap(on_37_bits, 5 * sizeof(int), prot, flags, 0, 0);
- mmap_addresses->on_38_addr =
- mmap(on_38_bits, 5 * sizeof(int), prot, flags, 0, 0);
- mmap_addresses->on_46_addr =
- mmap(on_46_bits, 5 * sizeof(int), prot, flags, 0, 0);
- mmap_addresses->on_47_addr =
- mmap(on_47_bits, 5 * sizeof(int), prot, flags, 0, 0);
- mmap_addresses->on_55_addr =
- mmap(on_55_bits, 5 * sizeof(int), prot, flags, 0, 0);
- mmap_addresses->on_56_addr =
- mmap(on_56_bits, 5 * sizeof(int), prot, flags, 0, 0);
+ return max_bit + (max_bit - 1);
}
+#define TEST_MMAPS \
+ ({ \
+ void *mmap_addr; \
+ for (int i = 0; i < ARRAY_SIZE(random_addresses); i++) { \
+ mmap_addr = mmap((void *)random_addresses[i], \
+ 5 * sizeof(int), PROT, FLAGS, 0, 0); \
+ EXPECT_NE(MAP_FAILED, mmap_addr); \
+ EXPECT_GE((void *)get_max_value(random_addresses[i]), \
+ mmap_addr); \
+ mmap_addr = mmap((void *)random_addresses[i], \
+ 5 * sizeof(int), PROT, FLAGS, 0, 0); \
+ EXPECT_NE(MAP_FAILED, mmap_addr); \
+ EXPECT_GE((void *)get_max_value(random_addresses[i]), \
+ mmap_addr); \
+ } \
+ })
+
static inline int memory_layout(void)
{
- int prot = PROT_READ | PROT_WRITE;
- int flags = MAP_PRIVATE | MAP_ANONYMOUS;
-
- void *value1 = mmap(NULL, sizeof(int), prot, flags, 0, 0);
- void *value2 = mmap(NULL, sizeof(int), prot, flags, 0, 0);
+ void *value1 = mmap(NULL, sizeof(int), PROT, FLAGS, 0, 0);
+ void *value2 = mmap(NULL, sizeof(int), PROT, FLAGS, 0, 0);
return value2 > value1;
}
--
2.43.0
Define mmap on riscv to not provide an address that uses more bits than
the hint address, if provided.
Signed-off-by: Charlie Jenkins <[email protected]>
---
Documentation/arch/riscv/vm-layout.rst | 16 +++++-----------
1 file changed, 5 insertions(+), 11 deletions(-)
diff --git a/Documentation/arch/riscv/vm-layout.rst b/Documentation/arch/riscv/vm-layout.rst
index 69ff6da1dbf8..e476b4386bd9 100644
--- a/Documentation/arch/riscv/vm-layout.rst
+++ b/Documentation/arch/riscv/vm-layout.rst
@@ -144,14 +144,8 @@ passing 0 into the hint address parameter of mmap. On CPUs with an address space
smaller than sv48, the CPU maximum supported address space will be the default.
Software can "opt-in" to receiving VAs from another VA space by providing
-a hint address to mmap. A hint address passed to mmap will cause the largest
-address space that fits entirely into the hint to be used, unless there is no
-space left in the address space. If there is no space available in the requested
-address space, an address in the next smallest available address space will be
-returned.
-
-For example, in order to obtain 48-bit VA space, a hint address greater than
-:code:`1 << 47` must be provided. Note that this is 47 due to sv48 userspace
-ending at :code:`1 << 47` and the addresses beyond this are reserved for the
-kernel. Similarly, to obtain 57-bit VA space addresses, a hint address greater
-than or equal to :code:`1 << 56` must be provided.
+a hint address to mmap. When a hint address is passed to mmap, the returned
+address will never use more bits than the hint address. For example, if a hint
+address of `1 << 40` is passed to mmap, a valid returned address will never use
+bits 41 through 63. If no mappable addresses are available in that range, mmap
+will return `MAP_FAILED`.
--
2.43.0
Hello:
This series was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <[email protected]>:
On Tue, 30 Jan 2024 17:06:59 -0800 you wrote:
> On riscv, mmap currently returns an address from the largest address
> space that can fit entirely inside of the hint address. This makes it
> such that the hint address is almost never returned. This patch raises
> the mappable area up to and including the hint address. This allows mmap
> to often return the hint address, which allows a performance improvement
> over searching for a valid address as well as making the behavior more
> similar to other architectures.
>
> [...]
Here is the summary with links:
- [v3,1/3] riscv: mm: Use hint address in mmap if available
https://git.kernel.org/riscv/c/b5b4287accd7
- [v3,2/3] selftests: riscv: Generalize mm selftests
https://git.kernel.org/riscv/c/73d05262a2ca
- [v3,3/3] docs: riscv: Define behavior of mmap
https://git.kernel.org/riscv/c/371a3c2055db
You are awesome, thank you!
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