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qemu-kvm/SOURCES/kvm-util-userfaultfd-Add-uf...

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From 80445fed73a7d1a87e8ce96f6cb7d505e437f845 Mon Sep 17 00:00:00 2001
From: Peter Xu <peterx@redhat.com>
Date: Wed, 1 Feb 2023 16:10:54 -0500
Subject: [PATCH 4/8] util/userfaultfd: Add uffd_open()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
RH-Author: Peter Xu <peterx@redhat.com>
RH-MergeRequest: 149: Support /dev/userfaultfd
RH-Bugzilla: 2158704
RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
RH-Acked-by: quintela1 <quintela@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Commit: [2/3] 4c81696314ab26db47c3415fa2c2501c6a572b5c (peterx/qemu-kvm)
Add a helper to create the uffd handle.
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
(cherry picked from commit d5890ea0722831eea76a0efd23a496b3e8815fe8)
Signed-off-by: Peter Xu <peterx@redhat.com>
---
include/qemu/userfaultfd.h | 12 ++++++++++++
migration/postcopy-ram.c | 11 +++++------
tests/qtest/migration-test.c | 4 ++--
util/userfaultfd.c | 13 +++++++++++--
4 files changed, 30 insertions(+), 10 deletions(-)
diff --git a/include/qemu/userfaultfd.h b/include/qemu/userfaultfd.h
index 6b74f92792..d764496f0b 100644
--- a/include/qemu/userfaultfd.h
+++ b/include/qemu/userfaultfd.h
@@ -13,10 +13,20 @@
#ifndef USERFAULTFD_H
#define USERFAULTFD_H
+#ifdef CONFIG_LINUX
+
#include "qemu/osdep.h"
#include "exec/hwaddr.h"
#include <linux/userfaultfd.h>
+/**
+ * uffd_open(): Open an userfaultfd handle for current context.
+ *
+ * @flags: The flags we want to pass in when creating the handle.
+ *
+ * Returns: the uffd handle if >=0, or <0 if error happens.
+ */
+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);
@@ -32,4 +42,6 @@ int uffd_wakeup(int uffd_fd, void *addr, uint64_t length);
int uffd_read_events(int uffd_fd, struct uffd_msg *msgs, int count);
bool uffd_poll_events(int uffd_fd, int tmo);
+#endif /* CONFIG_LINUX */
+
#endif /* USERFAULTFD_H */
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 dbde726adf..0100e1bdbc 100644
--- a/tests/qtest/migration-test.c
+++ b/tests/qtest/migration-test.c
@@ -61,14 +61,14 @@ static bool uffd_feature_thread_id;
#if defined(__linux__) && defined(__NR_userfaultfd) && defined(CONFIG_EVENTFD)
#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..4953b3137d 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(__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;
--
2.31.1
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