diff mbox series

[2/3] util/userfaultfd: Add uffd_open()

Message ID 20230125224016.212529-3-peterx@redhat.com (mailing list archive)
State New, archived
Headers show
Series util/userfaultfd: Support /dev/userfaultfd | expand

Commit Message

Peter Xu Jan. 25, 2023, 10:40 p.m. UTC 
Add a helper to create the uffd handle.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/qemu/userfaultfd.h   |  1 +
 migration/postcopy-ram.c     | 11 +++++------
 tests/qtest/migration-test.c |  3 ++-
 util/userfaultfd.c           | 13 +++++++++++--
 4 files changed, 19 insertions(+), 9 deletions(-)

Comments

Philippe Mathieu-Daudé Jan. 25, 2023, 11:04 p.m. UTC | #1 
On 25/1/23 23:40, Peter Xu wrote:
> Add a helper to create the uffd handle.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>   include/qemu/userfaultfd.h   |  1 +
>   migration/postcopy-ram.c     | 11 +++++------
>   tests/qtest/migration-test.c |  3 ++-
>   util/userfaultfd.c           | 13 +++++++++++--
>   4 files changed, 19 insertions(+), 9 deletions(-)
> 
> diff --git a/include/qemu/userfaultfd.h b/include/qemu/userfaultfd.h
> index 6b74f92792..a19a05d5f7 100644
> --- a/include/qemu/userfaultfd.h
> +++ b/include/qemu/userfaultfd.h
> @@ -17,6 +17,7 @@
>   #include "exec/hwaddr.h"
>   #include <linux/userfaultfd.h>
>   
> +int uffd_open(int flags);

Preferably documenting what this function returns:
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Peter Xu Jan. 26, 2023, 3:58 p.m. UTC | #2 
On Thu, Jan 26, 2023 at 12:04:35AM +0100, Philippe Mathieu-Daudé wrote:
> On 25/1/23 23:40, Peter Xu wrote:
> > Add a helper to create the uffd handle.
> > 
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> >   include/qemu/userfaultfd.h   |  1 +
> >   migration/postcopy-ram.c     | 11 +++++------
> >   tests/qtest/migration-test.c |  3 ++-
> >   util/userfaultfd.c           | 13 +++++++++++--
> >   4 files changed, 19 insertions(+), 9 deletions(-)
> > 
> > diff --git a/include/qemu/userfaultfd.h b/include/qemu/userfaultfd.h
> > index 6b74f92792..a19a05d5f7 100644
> > --- a/include/qemu/userfaultfd.h
> > +++ b/include/qemu/userfaultfd.h
> > @@ -17,6 +17,7 @@
> >   #include "exec/hwaddr.h"
> >   #include <linux/userfaultfd.h>
> > +int uffd_open(int flags);
> 
> Preferably documenting what this function returns:

Sure thing.

> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Thanks,
diff mbox series

Patch

diff --git a/include/qemu/userfaultfd.h b/include/qemu/userfaultfd.h
index 6b74f92792..a19a05d5f7 100644
--- a/include/qemu/userfaultfd.h
+++ b/include/qemu/userfaultfd.h
@@ -17,6 +17,7 @@ 
 #include "exec/hwaddr.h"
 #include <linux/userfaultfd.h>
 
+int uffd_open(int flags);
 int uffd_query_features(uint64_t *features);
 int uffd_create_fd(uint64_t features, bool non_blocking);
 void uffd_close_fd(int uffd_fd);
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index b9a37ef255..0c55df0e52 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -37,6 +37,7 @@ 
 #include "qemu-file.h"
 #include "yank_functions.h"
 #include "tls.h"
+#include "qemu/userfaultfd.h"
 
 /* Arbitrary limit on size of each discard command,
  * keeps them around ~200 bytes
@@ -226,11 +227,9 @@  static bool receive_ufd_features(uint64_t *features)
     int ufd;
     bool ret = true;
 
-    /* if we are here __NR_userfaultfd should exists */
-    ufd = syscall(__NR_userfaultfd, O_CLOEXEC);
+    ufd = uffd_open(O_CLOEXEC);
     if (ufd == -1) {
-        error_report("%s: syscall __NR_userfaultfd failed: %s", __func__,
-                     strerror(errno));
+        error_report("%s: uffd_open() failed: %s", __func__, strerror(errno));
         return false;
     }
 
@@ -375,7 +374,7 @@  bool postcopy_ram_supported_by_host(MigrationIncomingState *mis)
         goto out;
     }
 
-    ufd = syscall(__NR_userfaultfd, O_CLOEXEC);
+    ufd = uffd_open(O_CLOEXEC);
     if (ufd == -1) {
         error_report("%s: userfaultfd not available: %s", __func__,
                      strerror(errno));
@@ -1160,7 +1159,7 @@  static int postcopy_temp_pages_setup(MigrationIncomingState *mis)
 int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
 {
     /* Open the fd for the kernel to give us userfaults */
-    mis->userfault_fd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
+    mis->userfault_fd = uffd_open(O_CLOEXEC | O_NONBLOCK);
     if (mis->userfault_fd == -1) {
         error_report("%s: Failed to open userfault fd: %s", __func__,
                      strerror(errno));
diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
index 1dd32c9506..7a5d1922dd 100644
--- a/tests/qtest/migration-test.c
+++ b/tests/qtest/migration-test.c
@@ -62,13 +62,14 @@  static bool uffd_feature_thread_id;
 #include <sys/eventfd.h>
 #include <sys/ioctl.h>
 #include <linux/userfaultfd.h>
+#include "qemu/userfaultfd.h"
 
 static bool ufd_version_check(void)
 {
     struct uffdio_api api_struct;
     uint64_t ioctl_mask;
 
-    int ufd = syscall(__NR_userfaultfd, O_CLOEXEC);
+    int ufd = uffd_open(O_CLOEXEC);
 
     if (ufd == -1) {
         g_test_message("Skipping test: userfaultfd not available");
diff --git a/util/userfaultfd.c b/util/userfaultfd.c
index f1cd6af2b1..9845a2ec81 100644
--- a/util/userfaultfd.c
+++ b/util/userfaultfd.c
@@ -19,6 +19,15 @@ 
 #include <sys/syscall.h>
 #include <sys/ioctl.h>
 
+int uffd_open(int flags)
+{
+#if defined(__linux__) && defined(__NR_userfaultfd)
+    return syscall(__NR_userfaultfd, flags);
+#else
+    return -EINVAL;
+#endif
+}
+
 /**
  * uffd_query_features: query UFFD features
  *
@@ -32,7 +41,7 @@  int uffd_query_features(uint64_t *features)
     struct uffdio_api api_struct = { 0 };
     int ret = -1;
 
-    uffd_fd = syscall(__NR_userfaultfd, O_CLOEXEC);
+    uffd_fd = uffd_open(O_CLOEXEC);
     if (uffd_fd < 0) {
         trace_uffd_query_features_nosys(errno);
         return -1;
@@ -69,7 +78,7 @@  int uffd_create_fd(uint64_t features, bool non_blocking)
     uint64_t ioctl_mask = BIT(_UFFDIO_REGISTER) | BIT(_UFFDIO_UNREGISTER);
 
     flags = O_CLOEXEC | (non_blocking ? O_NONBLOCK : 0);
-    uffd_fd = syscall(__NR_userfaultfd, flags);
+    uffd_fd = uffd_open(flags);
     if (uffd_fd < 0) {
         trace_uffd_create_fd_nosys(errno);
         return -1;