Clang's integrated assembler does not allow symbols with non-absolute
values to be reassigned. Modify the interrupt entry loop macro to be
compatible with IAS by using a label and an offset.
Cc: Jian Cai <caij2003(a)gmail.com>
Signed-off-by: Bill Wendling <morbo(a)google.com>
References: https://lore.kernel.org/lkml/20200714233024.1789985-1-caij2003@gmail.com/
---
tools/testing/selftests/kvm/lib/x86_64/handlers.S | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/kvm/lib/x86_64/handlers.S b/tools/testing/selftests/kvm/lib/x86_64/handlers.S
index aaf7bc7d2ce1..3f9181e9a0a7 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/handlers.S
+++ b/tools/testing/selftests/kvm/lib/x86_64/handlers.S
@@ -54,9 +54,9 @@ idt_handlers:
.align 8
/* Fetch current address and append it to idt_handlers. */
- current_handler = .
+0 :
.pushsection .rodata
-.quad current_handler
+ .quad 0b
.popsection
.if ! \has_error
--
2.29.2.576.ga3fc446d84-goog
I'm just starting my learning curve on SGX, so I don't know if I've missed
some setup for the SGX device entries. After looking at arch/x86/kernel/cpu/sgx/driver.c
I see that there is no mode value for either sgx_dev_enclave or sgx_dev_provision.
With this patch I can get the SGX self test to complete:
sudo ./test_sgx
Warning: no execute permissions on device file /dev/sgx_enclave
0x0000000000000000 0x0000000000002000 0x03
0x0000000000002000 0x0000000000001000 0x05
0x0000000000003000 0x0000000000003000 0x03
SUCCESS
Is the warning even necessary ?
Tim
Functionally, this just means that the test output will be slightly
changed and it'll now depend on CONFIG_KUNIT=y/m.
It'll still run at boot time and can still be built as a loadable
module.
There was a pre-existing patch to convert this test that I found later,
here [1]. Compared to [1], this patch doesn't rename files and uses
KUnit features more heavily (i.e. does more than converting pr_err()
calls to KUNIT_FAIL()).
What this conversion gives us:
* a shorter test thanks to KUnit's macros
* a way to run this a bit more easily via kunit.py (and
CONFIG_KUNIT_ALL_TESTS=y) [2]
* a structured way of reporting pass/fail
* uses kunit-managed allocations to avoid the risk of memory leaks
* more descriptive error messages:
* i.e. it prints out which fields are invalid, what the expected
values are, etc.
What this conversion does not do:
* change the name of the file (and thus the name of the module)
* change the name of the config option
Leaving these as-is for now to minimize the impact to people wanting to
run this test. IMO, that concern trumps following KUnit's style guide
for both names, at least for now.
[1] https://lore.kernel.org/linux-kselftest/20201015014616.309000-1-vitor@massa…
[2] Can be run via
$ ./tools/testing/kunit/kunit.py run --kunitconfig /dev/stdin <<EOF
CONFIG_KUNIT=y
CONFIG_TEST_LIST_SORT=y
EOF
[16:55:56] Configuring KUnit Kernel ...
[16:55:56] Building KUnit Kernel ...
[16:56:29] Starting KUnit Kernel ...
[16:56:32] ============================================================
[16:56:32] ======== [PASSED] list_sort ========
[16:56:32] [PASSED] list_sort_test
[16:56:32] ============================================================
[16:56:32] Testing complete. 1 tests run. 0 failed. 0 crashed.
[16:56:32] Elapsed time: 35.668s total, 0.001s configuring, 32.725s building, 0.000s running
Note: the build time is as after a `make mrproper`.
Signed-off-by: Daniel Latypov <dlatypov(a)google.com>
---
lib/Kconfig.debug | 5 +-
lib/test_list_sort.c | 128 +++++++++++++++++--------------------------
2 files changed, 54 insertions(+), 79 deletions(-)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 417c3d3e521b..09a0cc8a55cc 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1999,8 +1999,9 @@ config LKDTM
Documentation/fault-injection/provoke-crashes.rst
config TEST_LIST_SORT
- tristate "Linked list sorting test"
- depends on DEBUG_KERNEL || m
+ tristate "Linked list sorting test" if !KUNIT_ALL_TESTS
+ depends on KUNIT
+ default KUNIT_ALL_TESTS
help
Enable this to turn on 'list_sort()' function test. This test is
executed only once during system boot (so affects only boot time),
diff --git a/lib/test_list_sort.c b/lib/test_list_sort.c
index 1f017d3b610e..ccfd98dbf57c 100644
--- a/lib/test_list_sort.c
+++ b/lib/test_list_sort.c
@@ -1,5 +1,5 @@
// SPDX-License-Identifier: GPL-2.0-only
-#define pr_fmt(fmt) "list_sort_test: " fmt
+#include <kunit/test.h>
#include <linux/kernel.h>
#include <linux/list_sort.h>
@@ -23,67 +23,52 @@ struct debug_el {
struct list_head list;
unsigned int poison2;
int value;
- unsigned serial;
+ unsigned int serial;
};
-/* Array, containing pointers to all elements in the test list */
-static struct debug_el **elts __initdata;
-
-static int __init check(struct debug_el *ela, struct debug_el *elb)
+static void check(struct kunit *test, struct debug_el *ela, struct debug_el *elb)
{
- if (ela->serial >= TEST_LIST_LEN) {
- pr_err("error: incorrect serial %d\n", ela->serial);
- return -EINVAL;
- }
- if (elb->serial >= TEST_LIST_LEN) {
- pr_err("error: incorrect serial %d\n", elb->serial);
- return -EINVAL;
- }
- if (elts[ela->serial] != ela || elts[elb->serial] != elb) {
- pr_err("error: phantom element\n");
- return -EINVAL;
- }
- if (ela->poison1 != TEST_POISON1 || ela->poison2 != TEST_POISON2) {
- pr_err("error: bad poison: %#x/%#x\n",
- ela->poison1, ela->poison2);
- return -EINVAL;
- }
- if (elb->poison1 != TEST_POISON1 || elb->poison2 != TEST_POISON2) {
- pr_err("error: bad poison: %#x/%#x\n",
- elb->poison1, elb->poison2);
- return -EINVAL;
- }
- return 0;
+ struct debug_el **elts = test->priv;
+
+ KUNIT_EXPECT_LT_MSG(test, ela->serial, (unsigned int)TEST_LIST_LEN, "incorrect serial");
+ KUNIT_EXPECT_LT_MSG(test, elb->serial, (unsigned int)TEST_LIST_LEN, "incorrect serial");
+
+ KUNIT_EXPECT_PTR_EQ_MSG(test, elts[ela->serial], ela, "phantom element");
+ KUNIT_EXPECT_PTR_EQ_MSG(test, elts[elb->serial], elb, "phantom element");
+
+ KUNIT_EXPECT_EQ_MSG(test, ela->poison1, TEST_POISON1, "bad poison");
+ KUNIT_EXPECT_EQ_MSG(test, ela->poison2, TEST_POISON2, "bad poison");
+
+ KUNIT_EXPECT_EQ_MSG(test, elb->poison1, TEST_POISON1, "bad poison");
+ KUNIT_EXPECT_EQ_MSG(test, elb->poison2, TEST_POISON2, "bad poison");
}
-static int __init cmp(void *priv, struct list_head *a, struct list_head *b)
+/* `priv` is the test pointer so check() can fail the test if the list is invalid. */
+static int cmp(void *priv, struct list_head *a, struct list_head *b)
{
struct debug_el *ela, *elb;
ela = container_of(a, struct debug_el, list);
elb = container_of(b, struct debug_el, list);
- check(ela, elb);
+ check(priv, ela, elb);
return ela->value - elb->value;
}
-static int __init list_sort_test(void)
+static void list_sort_test(struct kunit *test)
{
- int i, count = 1, err = -ENOMEM;
- struct debug_el *el;
+ int i, count = 1;
+ struct debug_el *el, **elts;
struct list_head *cur;
LIST_HEAD(head);
- pr_debug("start testing list_sort()\n");
-
- elts = kcalloc(TEST_LIST_LEN, sizeof(*elts), GFP_KERNEL);
- if (!elts)
- return err;
+ elts = kunit_kcalloc(test, TEST_LIST_LEN, sizeof(*elts), GFP_KERNEL);
+ KUNIT_ASSERT_NOT_ERR_OR_NULL(test, elts);
+ test->priv = elts;
for (i = 0; i < TEST_LIST_LEN; i++) {
- el = kmalloc(sizeof(*el), GFP_KERNEL);
- if (!el)
- goto exit;
+ el = kunit_kmalloc(test, sizeof(*el), GFP_KERNEL);
+ KUNIT_ASSERT_NOT_ERR_OR_NULL(test, el);
/* force some equivalencies */
el->value = prandom_u32() % (TEST_LIST_LEN / 3);
@@ -94,55 +79,44 @@ static int __init list_sort_test(void)
list_add_tail(&el->list, &head);
}
- list_sort(NULL, &head, cmp);
+ list_sort(test, &head, cmp);
- err = -EINVAL;
for (cur = head.next; cur->next != &head; cur = cur->next) {
struct debug_el *el1;
int cmp_result;
- if (cur->next->prev != cur) {
- pr_err("error: list is corrupted\n");
- goto exit;
- }
+ KUNIT_ASSERT_PTR_EQ_MSG(test, cur->next->prev, cur,
+ "list is corrupted");
- cmp_result = cmp(NULL, cur, cur->next);
- if (cmp_result > 0) {
- pr_err("error: list is not sorted\n");
- goto exit;
- }
+ cmp_result = cmp(test, cur, cur->next);
+ KUNIT_ASSERT_LE_MSG(test, cmp_result, 0, "list is not sorted");
el = container_of(cur, struct debug_el, list);
el1 = container_of(cur->next, struct debug_el, list);
- if (cmp_result == 0 && el->serial >= el1->serial) {
- pr_err("error: order of equivalent elements not "
- "preserved\n");
- goto exit;
+ if (cmp_result == 0) {
+ KUNIT_ASSERT_LE_MSG(test, el->serial, el1->serial,
+ "order of equivalent elements not preserved");
}
- if (check(el, el1)) {
- pr_err("error: element check failed\n");
- goto exit;
- }
+ check(test, el, el1);
count++;
}
- if (head.prev != cur) {
- pr_err("error: list is corrupted\n");
- goto exit;
- }
+ KUNIT_EXPECT_PTR_EQ_MSG(test, head.prev, cur, "list is corrupted");
+ KUNIT_EXPECT_EQ_MSG(test, count, TEST_LIST_LEN,
+ "list length changed after sorting!");
+}
- if (count != TEST_LIST_LEN) {
- pr_err("error: bad list length %d", count);
- goto exit;
- }
+static struct kunit_case list_sort_cases[] = {
+ KUNIT_CASE(list_sort_test),
+ {}
+};
+
+static struct kunit_suite list_sort_suite = {
+ .name = "list_sort",
+ .test_cases = list_sort_cases,
+};
+
+kunit_test_suites(&list_sort_suite);
- err = 0;
-exit:
- for (i = 0; i < TEST_LIST_LEN; i++)
- kfree(elts[i]);
- kfree(elts);
- return err;
-}
-module_init(list_sort_test);
MODULE_LICENSE("GPL");
--
2.31.1.498.g6c1eba8ee3d-goog
Add in:
* kunit_kmalloc_array() and wire up kunit_kmalloc() to be a special
case of it.
* kunit_kcalloc() for symmetry with kunit_kzalloc()
This should using KUnit more natural by making it more similar to the
existing *alloc() APIs.
And while we shouldn't necessarily be writing unit tests where overflow
should be a concern, it can't hurt to be safe.
Signed-off-by: Daniel Latypov <dlatypov(a)google.com>
Reviewed-by: David Gow <davidgow(a)google.com>
Reviewed-by: Brendan Higgins <brendanhiggins(a)google.com>
---
v1 -> v2: s/kzalloc/kcalloc in doc comment.
---
include/kunit/test.h | 36 ++++++++++++++++++++++++++++++++----
lib/kunit/test.c | 22 ++++++++++++----------
2 files changed, 44 insertions(+), 14 deletions(-)
diff --git a/include/kunit/test.h b/include/kunit/test.h
index 49601c4b98b8..e8ecb69dd567 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -577,16 +577,30 @@ static inline int kunit_destroy_named_resource(struct kunit *test,
void kunit_remove_resource(struct kunit *test, struct kunit_resource *res);
/**
- * kunit_kmalloc() - Like kmalloc() except the allocation is *test managed*.
+ * kunit_kmalloc_array() - Like kmalloc_array() except the allocation is *test managed*.
* @test: The test context object.
+ * @n: number of elements.
* @size: The size in bytes of the desired memory.
* @gfp: flags passed to underlying kmalloc().
*
- * Just like `kmalloc(...)`, except the allocation is managed by the test case
+ * Just like `kmalloc_array(...)`, except the allocation is managed by the test case
* and is automatically cleaned up after the test case concludes. See &struct
* kunit_resource for more information.
*/
-void *kunit_kmalloc(struct kunit *test, size_t size, gfp_t gfp);
+void *kunit_kmalloc_array(struct kunit *test, size_t n, size_t size, gfp_t flags);
+
+/**
+ * kunit_kmalloc() - Like kmalloc() except the allocation is *test managed*.
+ * @test: The test context object.
+ * @size: The size in bytes of the desired memory.
+ * @gfp: flags passed to underlying kmalloc().
+ *
+ * See kmalloc() and kunit_kmalloc_array() for more information.
+ */
+static inline void *kunit_kmalloc(struct kunit *test, size_t size, gfp_t gfp)
+{
+ return kunit_kmalloc_array(test, 1, size, gfp);
+}
/**
* kunit_kfree() - Like kfree except for allocations managed by KUnit.
@@ -601,13 +615,27 @@ void kunit_kfree(struct kunit *test, const void *ptr);
* @size: The size in bytes of the desired memory.
* @gfp: flags passed to underlying kmalloc().
*
- * See kzalloc() and kunit_kmalloc() for more information.
+ * See kzalloc() and kunit_kmalloc_array() for more information.
*/
static inline void *kunit_kzalloc(struct kunit *test, size_t size, gfp_t gfp)
{
return kunit_kmalloc(test, size, gfp | __GFP_ZERO);
}
+/**
+ * kunit_kcalloc() - Just like kunit_kmalloc_array(), but zeroes the allocation.
+ * @test: The test context object.
+ * @n: number of elements.
+ * @size: The size in bytes of the desired memory.
+ * @gfp: flags passed to underlying kmalloc().
+ *
+ * See kcalloc() and kunit_kmalloc_array() for more information.
+ */
+static inline void *kunit_kcalloc(struct kunit *test, size_t n, size_t size, gfp_t flags)
+{
+ return kunit_kmalloc_array(test, n, size, flags | __GFP_ZERO);
+}
+
void kunit_cleanup(struct kunit *test);
void kunit_log_append(char *log, const char *fmt, ...);
diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index 2f6cc0123232..41fa46b14c3b 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -573,41 +573,43 @@ int kunit_destroy_resource(struct kunit *test, kunit_resource_match_t match,
}
EXPORT_SYMBOL_GPL(kunit_destroy_resource);
-struct kunit_kmalloc_params {
+struct kunit_kmalloc_array_params {
+ size_t n;
size_t size;
gfp_t gfp;
};
-static int kunit_kmalloc_init(struct kunit_resource *res, void *context)
+static int kunit_kmalloc_array_init(struct kunit_resource *res, void *context)
{
- struct kunit_kmalloc_params *params = context;
+ struct kunit_kmalloc_array_params *params = context;
- res->data = kmalloc(params->size, params->gfp);
+ res->data = kmalloc_array(params->n, params->size, params->gfp);
if (!res->data)
return -ENOMEM;
return 0;
}
-static void kunit_kmalloc_free(struct kunit_resource *res)
+static void kunit_kmalloc_array_free(struct kunit_resource *res)
{
kfree(res->data);
}
-void *kunit_kmalloc(struct kunit *test, size_t size, gfp_t gfp)
+void *kunit_kmalloc_array(struct kunit *test, size_t n, size_t size, gfp_t gfp)
{
- struct kunit_kmalloc_params params = {
+ struct kunit_kmalloc_array_params params = {
.size = size,
+ .n = n,
.gfp = gfp
};
return kunit_alloc_resource(test,
- kunit_kmalloc_init,
- kunit_kmalloc_free,
+ kunit_kmalloc_array_init,
+ kunit_kmalloc_array_free,
gfp,
¶ms);
}
-EXPORT_SYMBOL_GPL(kunit_kmalloc);
+EXPORT_SYMBOL_GPL(kunit_kmalloc_array);
void kunit_kfree(struct kunit *test, const void *ptr)
{
base-commit: cda689f8708b6bef0b921c3a17fcdecbe959a079
--
2.31.1.527.g47e6f16901-goog
The readahead size used to be 2MB, thus it's reasonable to set the file
size as 4MB when checking check_file_mmap().
However since commit c2e4cd57cfa1 ("block: lift setting the readahead
size into the block layer"), readahead size could be as large as twice
the io_opt, and thus the hardcoded file size no longer works.
check_file_mmap() may report "Read-ahead pages reached the end of the
file" when the readahead size actually exceeds the file size in this
case.
To fix this issue, read the exact readahead window size via BLKRAGET
ioctl. Since now we have the readahead window size, take a more
fine-grained check. It is worth noting that this fine-grained check may
be broken as the sync readahead algorithm of kernel changes. It may be
acceptable since the algorithm of readahead ranging should be quite
stable, and we could tune the test case accorddingly if the algorithm
indeed changes.
Reported-by: James Wang <jnwang(a)linux.alibaba.com>
Acked-by: Ricardo Cañuelo <ricardo.canuelo(a)collabora.com>
Signed-off-by: Jeffle Xu <jefflexu(a)linux.alibaba.com>
---
changes since v3:
- make the check more fine-grained since we have the exact readahead
window size now, as suggested by Ricardo Cañuelo
chnages since v2:
- add 'Reported-by'
chnages since v1:
- add the test name "mincore" in the subject line
- add the error message in commit message
- rename @filesize to @file_size to keep a more consistent naming
convention
---
.../selftests/mincore/mincore_selftest.c | 96 +++++++++++++------
1 file changed, 68 insertions(+), 28 deletions(-)
diff --git a/tools/testing/selftests/mincore/mincore_selftest.c b/tools/testing/selftests/mincore/mincore_selftest.c
index 5a1e85ff5d32..369b35af4b4f 100644
--- a/tools/testing/selftests/mincore/mincore_selftest.c
+++ b/tools/testing/selftests/mincore/mincore_selftest.c
@@ -15,6 +15,11 @@
#include <string.h>
#include <fcntl.h>
#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/ioctl.h>
+#include <sys/sysmacros.h>
+#include <sys/mount.h>
#include "../kselftest.h"
#include "../kselftest_harness.h"
@@ -193,12 +198,44 @@ TEST(check_file_mmap)
int retval;
int page_size;
int fd;
- int i;
+ int i, start, end;
int ra_pages = 0;
+ long ra_size, file_size;
+ struct stat stats;
+ dev_t devt;
+ unsigned int major, minor;
+ char devpath[32];
+
+ retval = stat(".", &stats);
+ ASSERT_EQ(0, retval) {
+ TH_LOG("Can't stat pwd: %s", strerror(errno));
+ }
+
+ devt = stats.st_dev;
+ major = major(devt);
+ minor = minor(devt);
+ snprintf(devpath, sizeof(devpath), "/dev/block/%u:%u", major, minor);
+
+ fd = open(devpath, O_RDONLY);
+ ASSERT_NE(-1, fd) {
+ TH_LOG("Can't open underlying disk %s", strerror(errno));
+ }
+
+ retval = ioctl(fd, BLKRAGET, &ra_size);
+ ASSERT_EQ(0, retval) {
+ TH_LOG("Error ioctl with the underlying disk: %s", strerror(errno));
+ }
+
+ /*
+ * BLKRAGET ioctl returns the readahead size in sectors (512 bytes).
+ * Make file_size large enough to contain the readahead window.
+ */
+ ra_size *= 512;
+ file_size = ra_size * 2;
page_size = sysconf(_SC_PAGESIZE);
- vec_size = FILE_SIZE / page_size;
- if (FILE_SIZE % page_size)
+ vec_size = file_size / page_size;
+ if (file_size % page_size)
vec_size++;
vec = calloc(vec_size, sizeof(unsigned char));
@@ -213,7 +250,7 @@ TEST(check_file_mmap)
strerror(errno));
}
errno = 0;
- retval = fallocate(fd, 0, 0, FILE_SIZE);
+ retval = fallocate(fd, 0, 0, file_size);
ASSERT_EQ(0, retval) {
TH_LOG("Error allocating space for the temporary file: %s",
strerror(errno));
@@ -223,12 +260,12 @@ TEST(check_file_mmap)
* Map the whole file, the pages shouldn't be fetched yet.
*/
errno = 0;
- addr = mmap(NULL, FILE_SIZE, PROT_READ | PROT_WRITE,
+ addr = mmap(NULL, file_size, PROT_READ | PROT_WRITE,
MAP_SHARED, fd, 0);
ASSERT_NE(MAP_FAILED, addr) {
TH_LOG("mmap error: %s", strerror(errno));
}
- retval = mincore(addr, FILE_SIZE, vec);
+ retval = mincore(addr, file_size, vec);
ASSERT_EQ(0, retval);
for (i = 0; i < vec_size; i++) {
ASSERT_EQ(0, vec[i]) {
@@ -240,38 +277,41 @@ TEST(check_file_mmap)
* Touch a page in the middle of the mapping. We expect the next
* few pages (the readahead window) to be populated too.
*/
- addr[FILE_SIZE / 2] = 1;
- retval = mincore(addr, FILE_SIZE, vec);
+ addr[file_size / 2] = 1;
+ retval = mincore(addr, file_size, vec);
ASSERT_EQ(0, retval);
- ASSERT_EQ(1, vec[FILE_SIZE / 2 / page_size]) {
- TH_LOG("Page not found in memory after use");
- }
- i = FILE_SIZE / 2 / page_size + 1;
- while (i < vec_size && vec[i]) {
- ra_pages++;
- i++;
- }
- EXPECT_GT(ra_pages, 0) {
- TH_LOG("No read-ahead pages found in memory");
- }
+ /*
+ * Readahead window is [start, end). So far the sync readahead
+ * algorithm takes the page that triggers the page fault as the
+ * midpoint.
+ */
+ ra_pages = ra_size / page_size;
+ start = file_size / 2 / page_size - ra_pages / 2;
+ end = start + ra_pages;
- EXPECT_LT(i, vec_size) {
- TH_LOG("Read-ahead pages reached the end of the file");
+ /*
+ * Check there's no hole in the readahead window.
+ */
+ for (i = start; i < end; i++) {
+ ASSERT_EQ(1, vec[i]) {
+ TH_LOG("Hole found in read-ahead window");
+ }
}
+
/*
- * End of the readahead window. The rest of the pages shouldn't
- * be in memory.
+ * Check there's no page beyond the readahead window.
*/
- if (i < vec_size) {
- while (i < vec_size && !vec[i])
- i++;
- EXPECT_EQ(vec_size, i) {
+ for (i = 0; i < vec_size; i++) {
+ if (i == start)
+ i = end;
+
+ EXPECT_EQ(0, vec[i]) {
TH_LOG("Unexpected page in memory beyond readahead window");
}
}
- munmap(addr, FILE_SIZE);
+ munmap(addr, file_size);
close(fd);
free(vec);
}
--
2.27.0
It is documented in Documentation/admin-guide/hw-vuln/spectre.rst, that
disabling indirect branch speculation for a user-space process creates
more overhead and cause it to run slower. The performance hit varies by
CPU, but on the AMD A4-9120C and A6-9220C CPUs, a simple ping-pong using
pipes between two processes runs ~10x slower when disabling IB
speculation.
Patch 2, included in this RFC but not intended for commit, is a simple
program that demonstrates this issue. Running on a A4-9120C without IB
speculation disabled, each process ping-pong takes ~7us:
localhost ~ # taskset 1 /usr/local/bin/test
...
iters: 262144, t: 1936300, iter/sec: 135383, us/iter: 7
But when IB speculation is disabled, that number increases
significantly:
localhost ~ # taskset 1 /usr/local/bin/test d
...
iters: 16384, t: 1500518, iter/sec: 10918, us/iter: 91
Although this test is a worst-case scenario, we can also consider a real
situation: an audio server (i.e. pulse). If we imagine a low-latency
capture, with 10ms packets and a concurrent task on the same CPU (i.e.
video encoding, for a video call), the audio server will preempt the
CPU at a rate of 100HZ. At 91us overhead per preemption (switching to
and from the audio process), that's 0.9% overhead for one process doing
preemption. In real-world testing (on a A4-9120C), I've seen 9% of CPU
used by IBPB when doing a 2-person video call.
With this patch, the number of IBPBs issued can be reduced to the
minimum necessary, only when there's a potential attacker->victim
process switch.
Running on the same A4-9120C device, this patch reduces the performance
hit of IBPB by ~half, as expected:
localhost ~ # taskset 1 /usr/local/bin/test ds
...
iters: 32768, t: 1824043, iter/sec: 17964, us/iter: 55
It should be noted, CPUs from multiple vendors experience a performance
hit due to IBPB. I also tested a Intel i3-8130U which sees a noticable
(~2x) increase in process switch time due to IBPB.
IB spec enabled:
localhost ~ # taskset 1 /usr/local/bin/test
...
iters: 262144, t: 1210821us, iter/sec: 216501, us/iter: 4
IB spec disabled:
localhost ~ # taskset 1 /usr/local/bin/test d
...
iters: 131072, t: 1257583us, iter/sec: 104225, us/iter: 9
Open questions:
- There are a significant number of task flags, which also now reaches the
limit of the 'long' on 32-bit systems. Should the 'mode' flags be
stored somewhere else?
- Having x86-specific flags in linux/sched.h feels wrong. However, this
is the mechanism for doing atomic flag updates. Is there an alternate
approach?
Open tasks:
- Documentation
- Naming
Changes in v2:
- Make flag per-process using prctl().
Anand K Mistry (2):
x86/speculation: Allow per-process control of when to issue IBPB
selftests: Benchmark for the cost of disabling IB speculation
arch/x86/include/asm/thread_info.h | 4 +
arch/x86/kernel/cpu/bugs.c | 56 +++++++++
arch/x86/kernel/process.c | 10 ++
arch/x86/mm/tlb.c | 51 ++++++--
include/linux/sched.h | 10 ++
include/uapi/linux/prctl.h | 5 +
.../testing/selftests/ib_spec/ib_spec_bench.c | 109 ++++++++++++++++++
7 files changed, 236 insertions(+), 9 deletions(-)
create mode 100644 tools/testing/selftests/ib_spec/ib_spec_bench.c
--
2.31.1.498.g6c1eba8ee3d-goog
Hi, a friend and I were chasing bug 205219 [1] listed in Bugzilla.
We step into something a little bit different when trying to reproduce
the buggy behavior. In our try, compilation failed with a message form
make asking us to clean the source tree. We couldn't run kunit_tool
after compiling the kernel for x86, as described by Ted in the
discussion pointed out by the bug report.
Steps to reproduce:
0) Run kunit_tool
$ ./tools/testing/kunit/kunit.py run
Works fine with a clean tree.
1) Compile the kernel for some architecture (we did it for x86_64).
2) Run kunit_tool again
$ ./tools/testing/kunit/kunit.py run
Fails with a message form make asking us to clean the source tree.
Removing the clean source tree check from the top-level Makefile gives
us a similar error to what was described in the bug report. We see that
after running `git clean -fdx` kunit_tool runs nicely again. However,
this is not a real solution since some kernel binaries are erased by git.
We also had a look into the commit messages of Masahiro Yamada but
couldn't quite grasp why the check for the tree to be clean was added.
We could invest more time in this issue but actually don't know how to
proceed. We'd be glad to receive any comment about it. We could also try
something else if it's a too hard issue for beginners.
[1]: https://bugzilla.kernel.org/show_bug.cgi?id=205219
Best Regards,
Marcelo