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[PULL 02/14] os: add an ability to lock memory on_fault

Peter Xu posted 14 patches 1 month, 3 weeks ago
There is a newer version of this series
[PULL 02/14] os: add an ability to lock memory on_fault
Posted by Peter Xu 1 month, 3 weeks ago 
From: Daniil Tatianin <d-tatianin@yandex-team.ru>

This will be used in the following commits to make it possible to only
lock memory on fault instead of right away.

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
Link: https://lore.kernel.org/r/20250123131944.391886-2-d-tatianin@yandex-team.ru
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/system/os-posix.h |  2 +-
 include/system/os-win32.h |  3 ++-
 migration/postcopy-ram.c  |  2 +-
 os-posix.c                | 10 ++++++++--
 system/vl.c               |  2 +-
 5 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/include/system/os-posix.h b/include/system/os-posix.h
index b881ac6c6f..ce5b3bccf8 100644
--- a/include/system/os-posix.h
+++ b/include/system/os-posix.h
@@ -53,7 +53,7 @@ bool os_set_runas(const char *user_id);
 void os_set_chroot(const char *path);
 void os_setup_limits(void);
 void os_setup_post(void);
-int os_mlock(void);
+int os_mlock(bool on_fault);
 
 /**
  * qemu_alloc_stack:
diff --git a/include/system/os-win32.h b/include/system/os-win32.h
index b82a5d3ad9..cd61d69e10 100644
--- a/include/system/os-win32.h
+++ b/include/system/os-win32.h
@@ -123,8 +123,9 @@ static inline bool is_daemonized(void)
     return false;
 }
 
-static inline int os_mlock(void)
+static inline int os_mlock(bool on_fault)
 {
+    (void)on_fault;
     return -ENOSYS;
 }
 
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index 6a6da6ba7f..fc4d8a10df 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -652,7 +652,7 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
     }
 
     if (enable_mlock) {
-        if (os_mlock() < 0) {
+        if (os_mlock(false) < 0) {
             error_report("mlock: %s", strerror(errno));
             /*
              * It doesn't feel right to fail at this point, we have a valid
diff --git a/os-posix.c b/os-posix.c
index 9cce55ff2f..48afb2990d 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -327,18 +327,24 @@ void os_set_line_buffering(void)
     setvbuf(stdout, NULL, _IOLBF, 0);
 }
 
-int os_mlock(void)
+int os_mlock(bool on_fault)
 {
 #ifdef HAVE_MLOCKALL
     int ret = 0;
+    int flags = MCL_CURRENT | MCL_FUTURE;
 
-    ret = mlockall(MCL_CURRENT | MCL_FUTURE);
+    if (on_fault) {
+        flags |= MCL_ONFAULT;
+    }
+
+    ret = mlockall(flags);
     if (ret < 0) {
         error_report("mlockall: %s", strerror(errno));
     }
 
     return ret;
 #else
+    (void)on_fault;
     return -ENOSYS;
 #endif
 }
diff --git a/system/vl.c b/system/vl.c
index 9c6942c6cf..e94fc7ea35 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -797,7 +797,7 @@ static QemuOptsList qemu_run_with_opts = {
 static void realtime_init(void)
 {
     if (enable_mlock) {
-        if (os_mlock() < 0) {
+        if (os_mlock(false) < 0) {
             error_report("locking memory failed");
             exit(1);
         }
-- 
2.47.0
Re: [PULL 02/14] os: add an ability to lock memory on_fault
Posted by Stefan Hajnoczi 1 month, 3 weeks ago 
On Tue, Feb 11, 2025 at 5:52 PM Peter Xu <peterx@redhat.com> wrote:
>
> From: Daniil Tatianin <d-tatianin@yandex-team.ru>
>
> This will be used in the following commits to make it possible to only
> lock memory on fault instead of right away.

Hi Peter and Daniil,
Please take a look at this CI failure:
https://gitlab.com/qemu-project/qemu/-/jobs/9117106042#L3603

Thanks,
Stefan

>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> Reviewed-by: Peter Xu <peterx@redhat.com>
> Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
> Link: https://lore.kernel.org/r/20250123131944.391886-2-d-tatianin@yandex-team.ru
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  include/system/os-posix.h |  2 +-
>  include/system/os-win32.h |  3 ++-
>  migration/postcopy-ram.c  |  2 +-
>  os-posix.c                | 10 ++++++++--
>  system/vl.c               |  2 +-
>  5 files changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/include/system/os-posix.h b/include/system/os-posix.h
> index b881ac6c6f..ce5b3bccf8 100644
> --- a/include/system/os-posix.h
> +++ b/include/system/os-posix.h
> @@ -53,7 +53,7 @@ bool os_set_runas(const char *user_id);
>  void os_set_chroot(const char *path);
>  void os_setup_limits(void);
>  void os_setup_post(void);
> -int os_mlock(void);
> +int os_mlock(bool on_fault);
>
>  /**
>   * qemu_alloc_stack:
> diff --git a/include/system/os-win32.h b/include/system/os-win32.h
> index b82a5d3ad9..cd61d69e10 100644
> --- a/include/system/os-win32.h
> +++ b/include/system/os-win32.h
> @@ -123,8 +123,9 @@ static inline bool is_daemonized(void)
>      return false;
>  }
>
> -static inline int os_mlock(void)
> +static inline int os_mlock(bool on_fault)
>  {
> +    (void)on_fault;
>      return -ENOSYS;
>  }
>
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index 6a6da6ba7f..fc4d8a10df 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -652,7 +652,7 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
>      }
>
>      if (enable_mlock) {
> -        if (os_mlock() < 0) {
> +        if (os_mlock(false) < 0) {
>              error_report("mlock: %s", strerror(errno));
>              /*
>               * It doesn't feel right to fail at this point, we have a valid
> diff --git a/os-posix.c b/os-posix.c
> index 9cce55ff2f..48afb2990d 100644
> --- a/os-posix.c
> +++ b/os-posix.c
> @@ -327,18 +327,24 @@ void os_set_line_buffering(void)
>      setvbuf(stdout, NULL, _IOLBF, 0);
>  }
>
> -int os_mlock(void)
> +int os_mlock(bool on_fault)
>  {
>  #ifdef HAVE_MLOCKALL
>      int ret = 0;
> +    int flags = MCL_CURRENT | MCL_FUTURE;
>
> -    ret = mlockall(MCL_CURRENT | MCL_FUTURE);
> +    if (on_fault) {
> +        flags |= MCL_ONFAULT;
> +    }
> +
> +    ret = mlockall(flags);
>      if (ret < 0) {
>          error_report("mlockall: %s", strerror(errno));
>      }
>
>      return ret;
>  #else
> +    (void)on_fault;
>      return -ENOSYS;
>  #endif
>  }
> diff --git a/system/vl.c b/system/vl.c
> index 9c6942c6cf..e94fc7ea35 100644
> --- a/system/vl.c
> +++ b/system/vl.c
> @@ -797,7 +797,7 @@ static QemuOptsList qemu_run_with_opts = {
>  static void realtime_init(void)
>  {
>      if (enable_mlock) {
> -        if (os_mlock() < 0) {
> +        if (os_mlock(false) < 0) {
>              error_report("locking memory failed");
>              exit(1);
>          }
> --
> 2.47.0
>
>
Re: [PULL 02/14] os: add an ability to lock memory on_fault
Posted by Daniil Tatianin 1 month, 3 weeks ago 
On 2/12/25 5:13 PM, Stefan Hajnoczi wrote:
> On Tue, Feb 11, 2025 at 5:52 PM Peter Xu <peterx@redhat.com> wrote:
>> From: Daniil Tatianin <d-tatianin@yandex-team.ru>
>>
>> This will be used in the following commits to make it possible to only
>> lock memory on fault instead of right away.
> Hi Peter and Daniil,
> Please take a look at this CI failure:
> https://gitlab.com/qemu-project/qemu/-/jobs/9117106042#L3603
>
> Thanks,
> Stefan

Looks like MCL_ONFAULT is linux-only, I guess I'll have to have add 
something similar to HAVE_MLOCKALL and put this under an ifdef.

Thank you

>> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
>> Reviewed-by: Peter Xu <peterx@redhat.com>
>> Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
>> Link: https://lore.kernel.org/r/20250123131944.391886-2-d-tatianin@yandex-team.ru
>> Signed-off-by: Peter Xu <peterx@redhat.com>
>> ---
>>   include/system/os-posix.h |  2 +-
>>   include/system/os-win32.h |  3 ++-
>>   migration/postcopy-ram.c  |  2 +-
>>   os-posix.c                | 10 ++++++++--
>>   system/vl.c               |  2 +-
>>   5 files changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/system/os-posix.h b/include/system/os-posix.h
>> index b881ac6c6f..ce5b3bccf8 100644
>> --- a/include/system/os-posix.h
>> +++ b/include/system/os-posix.h
>> @@ -53,7 +53,7 @@ bool os_set_runas(const char *user_id);
>>   void os_set_chroot(const char *path);
>>   void os_setup_limits(void);
>>   void os_setup_post(void);
>> -int os_mlock(void);
>> +int os_mlock(bool on_fault);
>>
>>   /**
>>    * qemu_alloc_stack:
>> diff --git a/include/system/os-win32.h b/include/system/os-win32.h
>> index b82a5d3ad9..cd61d69e10 100644
>> --- a/include/system/os-win32.h
>> +++ b/include/system/os-win32.h
>> @@ -123,8 +123,9 @@ static inline bool is_daemonized(void)
>>       return false;
>>   }
>>
>> -static inline int os_mlock(void)
>> +static inline int os_mlock(bool on_fault)
>>   {
>> +    (void)on_fault;
>>       return -ENOSYS;
>>   }
>>
>> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
>> index 6a6da6ba7f..fc4d8a10df 100644
>> --- a/migration/postcopy-ram.c
>> +++ b/migration/postcopy-ram.c
>> @@ -652,7 +652,7 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
>>       }
>>
>>       if (enable_mlock) {
>> -        if (os_mlock() < 0) {
>> +        if (os_mlock(false) < 0) {
>>               error_report("mlock: %s", strerror(errno));
>>               /*
>>                * It doesn't feel right to fail at this point, we have a valid
>> diff --git a/os-posix.c b/os-posix.c
>> index 9cce55ff2f..48afb2990d 100644
>> --- a/os-posix.c
>> +++ b/os-posix.c
>> @@ -327,18 +327,24 @@ void os_set_line_buffering(void)
>>       setvbuf(stdout, NULL, _IOLBF, 0);
>>   }
>>
>> -int os_mlock(void)
>> +int os_mlock(bool on_fault)
>>   {
>>   #ifdef HAVE_MLOCKALL
>>       int ret = 0;
>> +    int flags = MCL_CURRENT | MCL_FUTURE;
>>
>> -    ret = mlockall(MCL_CURRENT | MCL_FUTURE);
>> +    if (on_fault) {
>> +        flags |= MCL_ONFAULT;
>> +    }
>> +
>> +    ret = mlockall(flags);
>>       if (ret < 0) {
>>           error_report("mlockall: %s", strerror(errno));
>>       }
>>
>>       return ret;
>>   #else
>> +    (void)on_fault;
>>       return -ENOSYS;
>>   #endif
>>   }
>> diff --git a/system/vl.c b/system/vl.c
>> index 9c6942c6cf..e94fc7ea35 100644
>> --- a/system/vl.c
>> +++ b/system/vl.c
>> @@ -797,7 +797,7 @@ static QemuOptsList qemu_run_with_opts = {
>>   static void realtime_init(void)
>>   {
>>       if (enable_mlock) {
>> -        if (os_mlock() < 0) {
>> +        if (os_mlock(false) < 0) {
>>               error_report("locking memory failed");
>>               exit(1);
>>           }
>> --
>> 2.47.0
>>
>>

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