util: Make qemu_prealloc_mem() optionally consume a ThreadContext

... and implement it under POSIX. When a ThreadContext is provided,
create new threads via the context such that these new threads obtain a
properly configured CPU affinity.

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Message-Id: <20221014134720.168738-6-david@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>

backends/hostmem.c

@@ -232,7 +232,8 @@ static void host_memory_backend_set_prealloc(Object *obj, bool value,
         void *ptr = memory_region_get_ram_ptr(&backend->mr);
         uint64_t sz = memory_region_size(&backend->mr);
 
-        qemu_prealloc_mem(fd, ptr, sz, backend->prealloc_threads, &local_err);
+        qemu_prealloc_mem(fd, ptr, sz, backend->prealloc_threads, NULL,
+                          &local_err);
         if (local_err) {
             error_propagate(errp, local_err);
             return;
@@ -384,7 +385,7 @@ host_memory_backend_memory_complete(UserCreatable *uc, Error **errp)
          */
         if (backend->prealloc) {
             qemu_prealloc_mem(memory_region_get_fd(&backend->mr), ptr, sz,
-                              backend->prealloc_threads, &local_err);
+                              backend->prealloc_threads, NULL, &local_err);
             if (local_err) {
                 goto out;
             }

hw/virtio/virtio-mem.c

@@ -467,7 +467,7 @@ static int virtio_mem_set_block_state(VirtIOMEM *vmem, uint64_t start_gpa,
             int fd = memory_region_get_fd(&vmem->memdev->mr);
             Error *local_err = NULL;
 
-            qemu_prealloc_mem(fd, area, size, 1, &local_err);
+            qemu_prealloc_mem(fd, area, size, 1, NULL, &local_err);
             if (local_err) {
                 static bool warned;
 

include/qemu/osdep.h

@@ -568,6 +568,8 @@ unsigned long qemu_getauxval(unsigned long type);
 
 void qemu_set_tty_echo(int fd, bool echo);
 
+typedef struct ThreadContext ThreadContext;
+
 /**
  * qemu_prealloc_mem:
  * @fd: the fd mapped into the area, -1 for anonymous memory
@@ -582,7 +584,7 @@ void qemu_set_tty_echo(int fd, bool echo);
  * after allocating file blocks for mapped files.
  */
 void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
-                       Error **errp);
+                       ThreadContext *tc, Error **errp);
 
 /**
  * qemu_get_pid_name:

util/oslib-posix.c

@@ -419,7 +419,8 @@ static inline int get_memset_num_threads(size_t hpagesize, size_t numpages,
 }
 
 static int touch_all_pages(char *area, size_t hpagesize, size_t numpages,
-                           int max_threads, bool use_madv_populate_write)
+                           int max_threads, ThreadContext *tc,
+                           bool use_madv_populate_write)
 {
     static gsize initialized = 0;
     MemsetContext context = {
@@ -458,9 +459,16 @@ static int touch_all_pages(char *area, size_t hpagesize, size_t numpages,
         context.threads[i].numpages = numpages_per_thread + (i < leftover);
         context.threads[i].hpagesize = hpagesize;
         context.threads[i].context = &context;
+        if (tc) {
+            thread_context_create_thread(tc, &context.threads[i].pgthread,
+                                         "touch_pages",
+                                         touch_fn, &context.threads[i],
+                                         QEMU_THREAD_JOINABLE);
+        } else {
             qemu_thread_create(&context.threads[i].pgthread, "touch_pages",
                                touch_fn, &context.threads[i],
                                QEMU_THREAD_JOINABLE);
+        }
         addr += context.threads[i].numpages * hpagesize;
     }
 
@@ -496,7 +504,7 @@ static bool madv_populate_write_possible(char *area, size_t pagesize)
 }
 
 void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
-                       Error **errp)
+                       ThreadContext *tc, Error **errp)
 {
     static gsize initialized;
     int ret;
@@ -537,7 +545,7 @@ void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
     }
 
     /* touch pages simultaneously */
-    ret = touch_all_pages(area, hpagesize, numpages, max_threads,
+    ret = touch_all_pages(area, hpagesize, numpages, max_threads, tc,
                           use_madv_populate_write);
     if (ret) {
         error_setg_errno(errp, -ret,

util/oslib-win32.c

@@ -269,7 +269,7 @@ int getpagesize(void)
 }
 
 void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
-                       Error **errp)
+                       ThreadContext *tc, Error **errp)
 {
     int i;
     size_t pagesize = qemu_real_host_page_size();