Re: [PATCH v7 1/3] mm: add new api to enable ksm per process

Re: [PATCH v7 1/3] mm: add new api to enable ksm per process

[David Hildenbrand]

Thanks!

In general,

Acked-by: David Hildenbrand <david@redhat.com>

Two nits below, after staring at some other prctl implementations.

> +#define PR_SET_MEMORY_MERGE		67
> +#define PR_GET_MEMORY_MERGE		68
>   #endif /* _LINUX_PRCTL_H */
> diff --git a/kernel/sys.c b/kernel/sys.c
> index 495cd87d9bf4..8c2e50edeb18 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -15,6 +15,7 @@
>   #include <linux/highuid.h>
>   #include <linux/fs.h>
>   #include <linux/kmod.h>
> +#include <linux/ksm.h>
>   #include <linux/perf_event.h>
>   #include <linux/resource.h>
>   #include <linux/kernel.h>
> @@ -2661,6 +2662,30 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
>   	case PR_SET_VMA:
>   		error = prctl_set_vma(arg2, arg3, arg4, arg5);
>   		break;
> +#ifdef CONFIG_KSM
> +	case PR_SET_MEMORY_MERGE:

Looking at some other code (PR_SET_NO_NEW_PRIVS/ PR_SET_THP_DISABLE) I 
wonder if we also want

if (arg3 || arg4 || arg5)
	return -EINVAL;

For PR_GET_MEMORY_MERGE it looks good already.

> +		if (mmap_write_lock_killable(me->mm))
> +			return -EINTR;
> +
> +		if (arg2) {
> +			error = ksm_enable_merge_any(me->mm);
> +		} else {
> +			/*
> +			 * TODO: we might want disable KSM on all VMAs and
> +			 * trigger unsharing to completely disable KSM.
> +			 */
> +			clear_bit(MMF_VM_MERGE_ANY, &me->mm->flags);
> +			error = 0;
> +		}
> +		mmap_write_unlock(me->mm);
> +		break;
> +	case PR_GET_MEMORY_MERGE:
> +		if (arg2 || arg3 || arg4 || arg5)
> +			return -EINVAL;
> +
> +		error = !!test_bit(MMF_VM_MERGE_ANY, &me->mm->flags);
> +		break;
> +#endif
>   	default:
>   		error = -EINVAL;
>   		break;

[...]

> +/**
> + * ksm_enable_merge_any - Add mm to mm ksm list and enable merging on all
> + *                        compatible VMA's
> + *
> + * @mm:  Pointer to mm
> + *
> + * Returns 0 on success, otherwise error code
> + */
> +int ksm_enable_merge_any(struct mm_struct *mm)
> +{
> +	int err;
> +
> +	if (test_bit(MMF_VM_MERGE_ANY, &mm->flags))
> +		return -EINVAL;


I'm curious, why is enabling the prctl() supposed to fail if already 
enabled? (it would not fail if disabling and already disabled)

For example, PR_SET_THP_DISABLE/PR_SET_NO_NEW_PRIVS doesn't fail if 
already set.

-- 
Thanks,

David / dhildenb

Re: [PATCH v7 3/3] selftests/mm: add new selftests for KSM

[David Hildenbrand]

Thanks for moving the functional tests. Some more feedback forksm_functional_tests change. Writing tests in the
ksft testing framework can be a bit "special".


I'm seeing some weird test failures due to

prctl(PR_GET_MEMORY_MERGE, 0)

Apparently, these go away when using

prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0)

to explicitly force the other values to 0. Most probably, we should do that
for PR_SET_MEMORY_MERGE as well (especially if we check for the arguments as
well).

[...]

> @@ -15,8 +15,10 @@
>   #include <errno.h>
>   #include <fcntl.h>
>   #include <sys/mman.h>
> +#include <sys/prctl.h>
>   #include <sys/syscall.h>
>   #include <sys/ioctl.h>
> +#include <sys/wait.h>
>   #include <linux/userfaultfd.h>
>   
>   #include "../kselftest.h"
> @@ -326,9 +328,80 @@ static void test_unmerge_uffd_wp(void)
>   }
>   #endif
>   
> +/* Verify that KSM can be enabled / queried with prctl. */
> +static void test_ksm_prctl(void)

Maybe call this "test_prctl", because after all, these are all KSM tests.

> +{
> +	bool ret = false;
> +	int is_on;
> +	int is_off;
> +
> +	ksft_print_msg("[RUN] %s\n", __func__);
> +
> +	if (prctl(PR_SET_MEMORY_MERGE, 1)) {
> +		perror("prctl set");
> +		goto out;
> +	}
> +
> +	is_on = prctl(PR_GET_MEMORY_MERGE, 0);
> +	if (prctl(PR_SET_MEMORY_MERGE, 0)) {
> +		perror("prctl set");
> +		goto out;
> +	}
> +
> +	is_off = prctl(PR_GET_MEMORY_MERGE, 0);
> +	if (is_on && is_off)
> +		ret = true;
> +
> +out:
> +	ksft_test_result(ret, "prctl get / set\n");

The test fails if the kernel does not support PR_SET_MEMORY_MERGE.


I'd modify this test to:

(1) skip if the first PR_SET_MEMORY_MERGE=1 failed with EINVAL.
(2) distinguish for PR_GET_MEMORY_MERGE whether it returned an error or
     whether it returned a wrong value. Feel free to keep that as is, whatever
     you prefer.
(3) exit early for all failures, you get exactly one expected skip/pass/fail for the
     test and use specific test failure messages.
(4) Pass "0" for all other arguments of prctl.


Something like:

static void test_prctl(void)
{
	int ret;

	ksft_print_msg("[RUN] %s\n", __func__);

	ret = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);
	if (ret < 0 && errno == EINVAL){
		ksft_test_result_skip("PR_SET_MEMORY_MERGE not supported\n");
		return;
	} else if (ret) {
		ksft_test_result_fail("PR_SET_MEMORY_MERGE=1 failed\n");
		return;
	}

	ret = prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0);
	if (ret < 0) {
		ksft_test_result_fail("PR_GET_MEMORY_MERGE failed\n");
		return;
	} else if (ret != 1) {
		ksft_test_result_fail("PR_SET_MEMORY_MERGE=1 not effective\n");
		return;
	}

	ret = prctl(PR_SET_MEMORY_MERGE, 0, 0, 0, 0);
	if (ret){
		ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 failed\n");
		return;
	}

	ret = prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0);
	if (ret < 0) {
		ksft_test_result_fail("PR_GET_MEMORY_MERGE failed\n");
		return;
	} else if (ret != 0) {
		ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 not effective\n");
		return;
	}

	ksft_test_result_pass("Setting/clearing PR_SET_MEMORY_MERGE works\n");
}


> +}
> +
> +/* Verify that prctl ksm flag is inherited. */
> +static void test_ksm_fork(void)

Maybe call it "test_prctl_fork"

> +{
> +	int status;
> +	bool ret = false;
> +	pid_t child_pid;
> +
> +	ksft_print_msg("[RUN] %s\n", __func__);
> +
> +	if (prctl(PR_SET_MEMORY_MERGE, 1)) {
> +		ksft_test_result_fail("prctl failed\n");
> +		goto out;
> +	}
> +
> +	child_pid = fork();
> +	if (child_pid == 0) {
> +		int is_on = 
> +
> +		if (!is_on)
> +			exit(-1);
> +
> +		exit(0);
> +	}
> +
> +	if (child_pid < 0) {
> +		ksft_test_result_fail("child pid < 0\n");
> +		goto out;> +
> +	if (waitpid(child_pid, &status, 0) < 0 || WEXITSTATUS(status) != 0) {
> +		ksft_test_result_fail("wait pid < 0\n");
> +		goto out;
> +	}
> +
> +	if (prctl(PR_SET_MEMORY_MERGE, 0))
> +		ksft_test_result_fail("prctl 2 failed\n");
> +	else
> +		ret = true;
> +
> +out:
> +	ksft_test_result(ret, "ksm_flag is inherited\n");
> +}

Again, test fails if kernel support is not around.

I'd modify this test to:

(1) skip if the first PR_SET_MEMORY_MERGE=1 failed with EINVAL just as in the other test.
(2) Use a simple exit(prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0)); in the child.
(3) exit early for all failures, you get exactly one expected skip/pass/fail for the
     test and use specific test failure messages.
(4) Split up the waitpid() check to test what failed.
(5) Pass "0" for all other arguments of prctl.


Something like:

static void test_prctl_fork(void)
{
	int ret, status;
	pid_t child_pid;

	ksft_print_msg("[RUN] %s\n", __func__);

	ret = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);
	if (ret < 0 && errno == EINVAL){
		ksft_test_result_skip("PR_SET_MEMORY_MERGE not supported\n");
		return;
	} else if (ret) {
		ksft_test_result_fail("PR_SET_MEMORY_MERGE=1 failed\n");
		return;
	}

	child_pid = fork();
	if (!child_pid) {
		exit(prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0));
	} else if (child_pid < 0) {
		ksft_test_result_fail("fork() failed\n");
		return;
	}

	if (waitpid(child_pid, &status, 0) < 0) {
		ksft_test_result_fail("waitpid() failed\n");
		return;
	} else if (WEXITSTATUS(status) != 1) {
		ksft_test_result_fail("unexpected PR_GET_MEMORY_MERGE result in child\n");
		return;
	}

	if (prctl(PR_SET_MEMORY_MERGE, 0, 0, 0, 0)) {
		ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 failed\n");
		return;
	}

	ksft_test_result_pass("PR_SET_MEMORY_MERGE value is inherited\n");
}



> +
>   int main(int argc, char **argv)
>   {
> -	unsigned int tests = 2;
> +	unsigned int tests = 6;

Assuming you execute exactly one ksft_test_result_skip/fail/pass on every path of your two
test, this would become "4".

>   	int err;
>   
>   #ifdef __NR_userfaultfd
> @@ -358,6 +431,8 @@ int main(int argc, char **argv)
>   #ifdef __NR_userfaultfd
>   	test_unmerge_uffd_wp();
>   #endif
> +	test_ksm_prctl();
> +	test_ksm_fork();
>   


With above outlined changes (feel free to integrate what you consider valuable),
on an older kernel I get:

$ sudo ./ksm_functional_tests
TAP version 13
1..5
# [RUN] test_unmerge
ok 1 Pages were unmerged
# [RUN] test_unmerge_discarded
ok 2 Pages were unmerged
# [RUN] test_unmerge_uffd_wp
ok 3 Pages were unmerged
# [RUN] test_prctl
ok 4 # SKIP PR_SET_MEMORY_MERGE not supported
# [RUN] test_prctl_fork
ok 5 # SKIP PR_SET_MEMORY_MERGE not supported
# Totals: pass:3 fail:0 xfail:0 xpass:0 skip:2 error:0


On a kernel with your patch #1:

# ./ksm_functional_tests
TAP version 13
1..5
# [RUN] test_unmerge
ok 1 Pages were unmerged
# [RUN] test_unmerge_discarded
ok 2 Pages were unmerged
# [RUN] test_unmerge_uffd_wp
ok 3 Pages were unmerged
# [RUN] test_prctl
ok 4 Setting/clearing PR_SET_MEMORY_MERGE works
# [RUN] test_prctl_fork
ok 5 PR_SET_MEMORY_MERGE value is inherited
# Totals: pass:5 fail:0 xfail:0 xpass:0 skip:0 error:0




>   	err = ksft_get_fail_cnt();
>   	if (err)
> diff --git a/tools/testing/selftests/mm/ksm_tests.c b/tools/testing/selftests/mm/ksm_tests.c
> index f9eb4d67e0dd..35b3828d44b4 100644
> --- a/tools/testing/selftests/mm/ksm_tests.c
> +++ b/tools/testing/selftests/mm/ksm_tests.c
> @@ -1,6 +1,8 @@
>   // SPDX-License-Identifier: GPL-2.0

[...]


Changes to ksm_tests mostly look good. Two comments:


> -	if (ksm_merge_pages(map_ptr, page_size * page_count, start_time, timeout))
> +	if (ksm_merge_pages(merge_type, map_ptr, page_size * page_count, start_time, timeout))
>   		goto err_out;
>   
>   	/* verify that the right number of pages are merged */
>   	if (assert_ksm_pages_count(page_count)) {
>   		printf("OK\n");
> -		munmap(map_ptr, page_size * page_count);
> +		if (merge_type == KSM_MERGE_MADVISE)
> +			munmap(map_ptr, page_size * page_count);
> +		else if (merge_type == KSM_MERGE_PRCTL)
> +			prctl(PR_SET_MEMORY_MERGE, 0);

Are you sure that we don't want to unmap here? I'd assume we want to unmap in either way.

[...]

> +		case 'd':
> +			debug = 1;
> +			break;
>   		case 's':
>   			size_MB = atoi(optarg);
>   			if (size_MB <= 0) {
>   				printf("Size must be greater than 0\n");
>   				return KSFT_FAIL;
>   			}
> +		case 't':
> +			{
> +				int tmp = atoi(optarg);
> +
> +				if (tmp < 0 || tmp > KSM_MERGE_LAST) {
> +					printf("Invalid merge type\n");
> +					return KSFT_FAIL;
> +				}
> +				merge_type = atoi(optarg);

You can simply reuse tmp

merge_type = tmp;




-- 
Thanks,

David / dhildenb

Re: [PATCH v7 1/3] mm: add new api to enable ksm per process

[Stefan Roesch]

David Hildenbrand <david@redhat.com> writes:

> Thanks!
>
> In general,
>
> Acked-by: David Hildenbrand <david@redhat.com>
>
> Two nits below, after staring at some other prctl implementations.
>
>> +#define PR_SET_MEMORY_MERGE		67
>> +#define PR_GET_MEMORY_MERGE		68
>>   #endif /* _LINUX_PRCTL_H */
>> diff --git a/kernel/sys.c b/kernel/sys.c
>> index 495cd87d9bf4..8c2e50edeb18 100644
>> --- a/kernel/sys.c
>> +++ b/kernel/sys.c
>> @@ -15,6 +15,7 @@
>>   #include <linux/highuid.h>
>>   #include <linux/fs.h>
>>   #include <linux/kmod.h>
>> +#include <linux/ksm.h>
>>   #include <linux/perf_event.h>
>>   #include <linux/resource.h>
>>   #include <linux/kernel.h>
>> @@ -2661,6 +2662,30 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
>>   	case PR_SET_VMA:
>>   		error = prctl_set_vma(arg2, arg3, arg4, arg5);
>>   		break;
>> +#ifdef CONFIG_KSM
>> +	case PR_SET_MEMORY_MERGE:
>
> Looking at some other code (PR_SET_NO_NEW_PRIVS/ PR_SET_THP_DISABLE) I wonder if
> we also want
>
> if (arg3 || arg4 || arg5)
> 	return -EINVAL;
>
I added the above check. It requires that we always specify all
parameters in the test programs. I also changed them accordingly.

> For PR_GET_MEMORY_MERGE it looks good already.
>
>> +		if (mmap_write_lock_killable(me->mm))
>> +			return -EINTR;
>> +
>> +		if (arg2) {
>> +			error = ksm_enable_merge_any(me->mm);
>> +		} else {
>> +			/*
>> +			 * TODO: we might want disable KSM on all VMAs and
>> +			 * trigger unsharing to completely disable KSM.
>> +			 */
>> +			clear_bit(MMF_VM_MERGE_ANY, &me->mm->flags);
>> +			error = 0;
>> +		}
>> +		mmap_write_unlock(me->mm);
>> +		break;
>> +	case PR_GET_MEMORY_MERGE:
>> +		if (arg2 || arg3 || arg4 || arg5)
>> +			return -EINVAL;
>> +
>> +		error = !!test_bit(MMF_VM_MERGE_ANY, &me->mm->flags);
>> +		break;
>> +#endif
>>   	default:
>>   		error = -EINVAL;
>>   		break;
>
> [...]
>
>> +/**
>> + * ksm_enable_merge_any - Add mm to mm ksm list and enable merging on all
>> + *                        compatible VMA's
>> + *
>> + * @mm:  Pointer to mm
>> + *
>> + * Returns 0 on success, otherwise error code
>> + */
>> +int ksm_enable_merge_any(struct mm_struct *mm)
>> +{
>> +	int err;
>> +
>> +	if (test_bit(MMF_VM_MERGE_ANY, &mm->flags))
>> +		return -EINVAL;
>
>
> I'm curious, why is enabling the prctl() supposed to fail if already enabled?
> (it would not fail if disabling and already disabled)
>

I changed that to not return an error in that case.
>
> For example, PR_SET_THP_DISABLE/PR_SET_NO_NEW_PRIVS doesn't fail if already set.

Re: [PATCH v7 3/3] selftests/mm: add new selftests for KSM

[Stefan Roesch]

David Hildenbrand <david@redhat.com> writes:

> Thanks for moving the functional tests. Some more feedback forksm_functional_tests change. Writing tests in the
> ksft testing framework can be a bit "special".
>
>
> I'm seeing some weird test failures due to
>
> prctl(PR_GET_MEMORY_MERGE, 0)
>
> Apparently, these go away when using
>
> prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0)
>

I changed the test programs to always specify all the 5 parameters.

> to explicitly force the other values to 0. Most probably, we should do that
> for PR_SET_MEMORY_MERGE as well (especially if we check for the arguments as
> well).
>
> [...]
>
>> @@ -15,8 +15,10 @@
>>   #include <errno.h>
>>   #include <fcntl.h>
>>   #include <sys/mman.h>
>> +#include <sys/prctl.h>
>>   #include <sys/syscall.h>
>>   #include <sys/ioctl.h>
>> +#include <sys/wait.h>
>>   #include <linux/userfaultfd.h>
>>     #include "../kselftest.h"
>> @@ -326,9 +328,80 @@ static void test_unmerge_uffd_wp(void)
>>   }
>>   #endif
>>   +/* Verify that KSM can be enabled / queried with prctl. */
>> +static void test_ksm_prctl(void)
>
> Maybe call this "test_prctl", because after all, these are all KSM tests.
>

I renamed it to test_prctl in the next version.

>> +{
>> +	bool ret = false;
>> +	int is_on;
>> +	int is_off;
>> +
>> +	ksft_print_msg("[RUN] %s\n", __func__);
>> +
>> +	if (prctl(PR_SET_MEMORY_MERGE, 1)) {
>> +		perror("prctl set");
>> +		goto out;
>> +	}
>> +
>> +	is_on = prctl(PR_GET_MEMORY_MERGE, 0);
>> +	if (prctl(PR_SET_MEMORY_MERGE, 0)) {
>> +		perror("prctl set");
>> +		goto out;
>> +	}
>> +
>> +	is_off = prctl(PR_GET_MEMORY_MERGE, 0);
>> +	if (is_on && is_off)
>> +		ret = true;
>> +
>> +out:
>> +	ksft_test_result(ret, "prctl get / set\n");
>
> The test fails if the kernel does not support PR_SET_MEMORY_MERGE.
>
>
> I'd modify this test to:
>
> (1) skip if the first PR_SET_MEMORY_MERGE=1 failed with EINVAL.
> (2) distinguish for PR_GET_MEMORY_MERGE whether it returned an error or
>     whether it returned a wrong value. Feel free to keep that as is, whatever
>     you prefer.
> (3) exit early for all failures, you get exactly one expected skip/pass/fail for the
>     test and use specific test failure messages.
> (4) Pass "0" for all other arguments of prctl.
>
>
> Something like:
>
> static void test_prctl(void)
> {
> 	int ret;
>
> 	ksft_print_msg("[RUN] %s\n", __func__);
>
> 	ret = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);
> 	if (ret < 0 && errno == EINVAL){
> 		ksft_test_result_skip("PR_SET_MEMORY_MERGE not supported\n");
> 		return;
> 	} else if (ret) {
> 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=1 failed\n");
> 		return;
> 	}
>
> 	ret = prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0);
> 	if (ret < 0) {
> 		ksft_test_result_fail("PR_GET_MEMORY_MERGE failed\n");
> 		return;
> 	} else if (ret != 1) {
> 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=1 not effective\n");
> 		return;
> 	}
>
> 	ret = prctl(PR_SET_MEMORY_MERGE, 0, 0, 0, 0);
> 	if (ret){
> 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 failed\n");
> 		return;
> 	}
>
> 	ret = prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0);
> 	if (ret < 0) {
> 		ksft_test_result_fail("PR_GET_MEMORY_MERGE failed\n");
> 		return;
> 	} else if (ret != 0) {
> 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 not effective\n");
> 		return;
> 	}
>
> 	ksft_test_result_pass("Setting/clearing PR_SET_MEMORY_MERGE works\n");
> }
>
>

I made changes to the test program according to the code above.
>> +}
>> +
>> +/* Verify that prctl ksm flag is inherited. */
>> +static void test_ksm_fork(void)
>
> Maybe call it "test_prctl_fork"
>
I changed it to test_prctl_fork.

>> +{
>> +	int status;
>> +	bool ret = false;
>> +	pid_t child_pid;
>> +
>> +	ksft_print_msg("[RUN] %s\n", __func__);
>> +
>> +	if (prctl(PR_SET_MEMORY_MERGE, 1)) {
>> +		ksft_test_result_fail("prctl failed\n");
>> +		goto out;
>> +	}
>> +
>> +	child_pid = fork();
>> +	if (child_pid == 0) {
>> +		int is_on = +
>> +		if (!is_on)
>> +			exit(-1);
>> +
>> +		exit(0);
>> +	}
>> +
>> +	if (child_pid < 0) {
>> +		ksft_test_result_fail("child pid < 0\n");
>> +		goto out;> +
>> +	if (waitpid(child_pid, &status, 0) < 0 || WEXITSTATUS(status) != 0) {
>> +		ksft_test_result_fail("wait pid < 0\n");
>> +		goto out;
>> +	}
>> +
>> +	if (prctl(PR_SET_MEMORY_MERGE, 0))
>> +		ksft_test_result_fail("prctl 2 failed\n");
>> +	else
>> +		ret = true;
>> +
>> +out:
>> +	ksft_test_result(ret, "ksm_flag is inherited\n");
>> +}
>
> Again, test fails if kernel support is not around.
>
> I'd modify this test to:
>
> (1) skip if the first PR_SET_MEMORY_MERGE=1 failed with EINVAL just as in the other test.
> (2) Use a simple exit(prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0)); in the child.
> (3) exit early for all failures, you get exactly one expected skip/pass/fail for the
>     test and use specific test failure messages.
> (4) Split up the waitpid() check to test what failed.
> (5) Pass "0" for all other arguments of prctl.
>
>
> Something like:
>
> static void test_prctl_fork(void)
> {
> 	int ret, status;
> 	pid_t child_pid;
>
> 	ksft_print_msg("[RUN] %s\n", __func__);
>
> 	ret = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);
> 	if (ret < 0 && errno == EINVAL){
> 		ksft_test_result_skip("PR_SET_MEMORY_MERGE not supported\n");
> 		return;
> 	} else if (ret) {
> 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=1 failed\n");
> 		return;
> 	}
>
> 	child_pid = fork();
> 	if (!child_pid) {
> 		exit(prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0));
> 	} else if (child_pid < 0) {
> 		ksft_test_result_fail("fork() failed\n");
> 		return;
> 	}
>
> 	if (waitpid(child_pid, &status, 0) < 0) {
> 		ksft_test_result_fail("waitpid() failed\n");
> 		return;
> 	} else if (WEXITSTATUS(status) != 1) {
> 		ksft_test_result_fail("unexpected PR_GET_MEMORY_MERGE result in child\n");
> 		return;
> 	}
>
> 	if (prctl(PR_SET_MEMORY_MERGE, 0, 0, 0, 0)) {
> 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 failed\n");
> 		return;
> 	}
>
> 	ksft_test_result_pass("PR_SET_MEMORY_MERGE value is inherited\n");
> }
>
>
>

I made changes to the test program according to the code above.
>> +
>>   int main(int argc, char **argv)
>>   {
>> -	unsigned int tests = 2;
>> +	unsigned int tests = 6;
>
> Assuming you execute exactly one ksft_test_result_skip/fail/pass on every path of your two
> test, this would become "4".
>
Changed it to 4.
>>   	int err;
>>     #ifdef __NR_userfaultfd
>> @@ -358,6 +431,8 @@ int main(int argc, char **argv)
>>   #ifdef __NR_userfaultfd
>>   	test_unmerge_uffd_wp();
>>   #endif
>> +	test_ksm_prctl();
>> +	test_ksm_fork();
>>
>
>
> With above outlined changes (feel free to integrate what you consider valuable),
> on an older kernel I get:
>
> $ sudo ./ksm_functional_tests
> TAP version 13
> 1..5
> # [RUN] test_unmerge
> ok 1 Pages were unmerged
> # [RUN] test_unmerge_discarded
> ok 2 Pages were unmerged
> # [RUN] test_unmerge_uffd_wp
> ok 3 Pages were unmerged
> # [RUN] test_prctl
> ok 4 # SKIP PR_SET_MEMORY_MERGE not supported
> # [RUN] test_prctl_fork
> ok 5 # SKIP PR_SET_MEMORY_MERGE not supported
> # Totals: pass:3 fail:0 xfail:0 xpass:0 skip:2 error:0
>
>
> On a kernel with your patch #1:
>
> # ./ksm_functional_tests
> TAP version 13
> 1..5
> # [RUN] test_unmerge
> ok 1 Pages were unmerged
> # [RUN] test_unmerge_discarded
> ok 2 Pages were unmerged
> # [RUN] test_unmerge_uffd_wp
> ok 3 Pages were unmerged
> # [RUN] test_prctl
> ok 4 Setting/clearing PR_SET_MEMORY_MERGE works
> # [RUN] test_prctl_fork
> ok 5 PR_SET_MEMORY_MERGE value is inherited
> # Totals: pass:5 fail:0 xfail:0 xpass:0 skip:0 error:0
>
>
>
>
>>   	err = ksft_get_fail_cnt();
>>   	if (err)
>> diff --git a/tools/testing/selftests/mm/ksm_tests.c b/tools/testing/selftests/mm/ksm_tests.c
>> index f9eb4d67e0dd..35b3828d44b4 100644
>> --- a/tools/testing/selftests/mm/ksm_tests.c
>> +++ b/tools/testing/selftests/mm/ksm_tests.c
>> @@ -1,6 +1,8 @@
>>   // SPDX-License-Identifier: GPL-2.0
>
> [...]
>
>
> Changes to ksm_tests mostly look good. Two comments:
>
>
>> -	if (ksm_merge_pages(map_ptr, page_size * page_count, start_time, timeout))
>> +	if (ksm_merge_pages(merge_type, map_ptr, page_size * page_count, start_time, timeout))
>>   		goto err_out;
>>     	/* verify that the right number of pages are merged */
>>   	if (assert_ksm_pages_count(page_count)) {
>>   		printf("OK\n");
>> -		munmap(map_ptr, page_size * page_count);
>> +		if (merge_type == KSM_MERGE_MADVISE)
>> +			munmap(map_ptr, page_size * page_count);
>> +		else if (merge_type == KSM_MERGE_PRCTL)
>> +			prctl(PR_SET_MEMORY_MERGE, 0);
>
> Are you sure that we don't want to unmap here? I'd assume we want to unmap in either way.
>
> [...]
>
I changed it to always unmap.

>> +		case 'd':
>> +			debug = 1;
>> +			break;
>>   		case 's':
>>   			size_MB = atoi(optarg);
>>   			if (size_MB <= 0) {
>>   				printf("Size must be greater than 0\n");
>>   				return KSFT_FAIL;
>>   			}
>> +		case 't':
>> +			{
>> +				int tmp = atoi(optarg);
>> +
>> +				if (tmp < 0 || tmp > KSM_MERGE_LAST) {
>> +					printf("Invalid merge type\n");
>> +					return KSFT_FAIL;
>> +				}
>> +				merge_type = atoi(optarg);
>
> You can simply reuse tmp
>
> merge_type = tmp;

Changed it.

Re: [PATCH v7 3/3] selftests/mm: add new selftests for KSM

[David Hildenbrand]

On 14.04.23 22:54, Stefan Roesch wrote:
> 
> David Hildenbrand <david@redhat.com> writes:
> 
>> Thanks for moving the functional tests. Some more feedback forksm_functional_tests change. Writing tests in the
>> ksft testing framework can be a bit "special".
>>
>>
>> I'm seeing some weird test failures due to
>>
>> prctl(PR_GET_MEMORY_MERGE, 0)
>>
>> Apparently, these go away when using
>>
>> prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0)
>>
> 
> I changed the test programs to always specify all the 5 parameters.
> 

Thanks!

-- 
Thanks,

David / dhildenb