Merge remote-tracking branch 'remotes/stefanha-gitlab/tags/block-pull…

…-request' into staging

Pull request

This contains coroutine poll size scaling, virtiofsd rseq seccomp for new glibc
versions, and the QEMU C virtiofsd deprecation notice.

# gpg: Signature made Mon 14 Feb 2022 17:14:21 GMT
# gpg:                using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha-gitlab/tags/block-pull-request:
  util: adjust coroutine pool size to virtio block queue
  Deprecate C virtiofsd
  tools/virtiofsd: Add rseq syscall to the seccomp allowlist

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

docs/about/deprecated.rst

@@ -447,3 +447,20 @@ nanoMIPS ISA
 
 The ``nanoMIPS`` ISA has never been upstreamed to any compiler toolchain.
 As it is hard to generate binaries for it, declare it deprecated.
+
+Tools
+-----
+
+virtiofsd
+'''''''''
+
+There is a new Rust implementation of ``virtiofsd`` at
+``https://gitlab.com/virtio-fs/virtiofsd``;
+since this is now marked stable, new development should be done on that
+rather than the existing C version in the QEMU tree.
+The C version will still accept fixes and patches that
+are already in development for the moment, but will eventually
+be deleted from this tree.
+New deployments should use the Rust version, and existing systems
+should consider moving to it.  The command line and feature set
+is very close and moving should be simple.

hw/block/virtio-blk.c

@@ -32,6 +32,7 @@
 #include "hw/virtio/virtio-bus.h"
 #include "migration/qemu-file-types.h"
 #include "hw/virtio/virtio-access.h"
+#include "qemu/coroutine.h"
 
 /* Config size before the discard support (hide associated config fields) */
 #define VIRTIO_BLK_CFG_SIZE offsetof(struct virtio_blk_config, \
@@ -1214,6 +1215,8 @@ static void virtio_blk_device_realize(DeviceState *dev, Error **errp)
     for (i = 0; i < conf->num_queues; i++) {
         virtio_add_queue(vdev, conf->queue_size, virtio_blk_handle_output);
     }
+    qemu_coroutine_increase_pool_batch_size(conf->num_queues * conf->queue_size
+                                            / 2);
     virtio_blk_data_plane_create(vdev, conf, &s->dataplane, &err);
     if (err != NULL) {
         error_propagate(errp, err);
@@ -1250,6 +1253,8 @@ static void virtio_blk_device_unrealize(DeviceState *dev)
     for (i = 0; i < conf->num_queues; i++) {
         virtio_del_queue(vdev, i);
     }
+    qemu_coroutine_decrease_pool_batch_size(conf->num_queues * conf->queue_size
+                                            / 2);
     qemu_del_vm_change_state_handler(s->change);
     blockdev_mark_auto_del(s->blk);
     virtio_cleanup(vdev);

include/qemu/coroutine.h

@@ -331,6 +331,16 @@ void qemu_co_sleep_wake(QemuCoSleep *w);
  */
 void coroutine_fn yield_until_fd_readable(int fd);
 
+/**
+ * Increase coroutine pool size
+ */
+void qemu_coroutine_increase_pool_batch_size(unsigned int additional_pool_size);
+
+/**
+ * Devcrease coroutine pool size
+ */
+void qemu_coroutine_decrease_pool_batch_size(unsigned int additional_pool_size);
+
 #include "qemu/lockable.h"
 
 #endif /* QEMU_COROUTINE_H */

tools/virtiofsd/passthrough_seccomp.c

@@ -91,6 +91,9 @@ static const int syscall_allowlist[] = {
     SCMP_SYS(renameat2),
     SCMP_SYS(removexattr),
     SCMP_SYS(restart_syscall),
+#ifdef __NR_rseq
+    SCMP_SYS(rseq), /* required since glibc 2.35 */
+#endif
     SCMP_SYS(rt_sigaction),
     SCMP_SYS(rt_sigprocmask),
     SCMP_SYS(rt_sigreturn),

util/qemu-coroutine.c

@@ -20,12 +20,14 @@
 #include "qemu/coroutine_int.h"
 #include "block/aio.h"
 
+/** Initial batch size is 64, and is increased on demand */
 enum {
-    POOL_BATCH_SIZE = 64,
+    POOL_INITIAL_BATCH_SIZE = 64,
 };
 
 /** Free list to speed up creation */
 static QSLIST_HEAD(, Coroutine) release_pool = QSLIST_HEAD_INITIALIZER(pool);
+static unsigned int pool_batch_size = POOL_INITIAL_BATCH_SIZE;
 static unsigned int release_pool_size;
 static __thread QSLIST_HEAD(, Coroutine) alloc_pool = QSLIST_HEAD_INITIALIZER(pool);
 static __thread unsigned int alloc_pool_size;
@@ -49,7 +51,7 @@ Coroutine *qemu_coroutine_create(CoroutineEntry *entry, void *opaque)
     if (CONFIG_COROUTINE_POOL) {
         co = QSLIST_FIRST(&alloc_pool);
         if (!co) {
-            if (release_pool_size > POOL_BATCH_SIZE) {
+            if (release_pool_size > qatomic_read(&pool_batch_size)) {
                 /* Slow path; a good place to register the destructor, too.  */
                 if (!coroutine_pool_cleanup_notifier.notify) {
                     coroutine_pool_cleanup_notifier.notify = coroutine_pool_cleanup;
@@ -86,12 +88,12 @@ static void coroutine_delete(Coroutine *co)
     co->caller = NULL;
 
     if (CONFIG_COROUTINE_POOL) {
-        if (release_pool_size < POOL_BATCH_SIZE * 2) {
+        if (release_pool_size < qatomic_read(&pool_batch_size) * 2) {
             QSLIST_INSERT_HEAD_ATOMIC(&release_pool, co, pool_next);
             qatomic_inc(&release_pool_size);
             return;
         }
-        if (alloc_pool_size < POOL_BATCH_SIZE) {
+        if (alloc_pool_size < qatomic_read(&pool_batch_size)) {
             QSLIST_INSERT_HEAD(&alloc_pool, co, pool_next);
             alloc_pool_size++;
             return;
@@ -202,3 +204,13 @@ AioContext *coroutine_fn qemu_coroutine_get_aio_context(Coroutine *co)
 {
     return co->ctx;
 }
+
+void qemu_coroutine_increase_pool_batch_size(unsigned int additional_pool_size)
+{
+    qatomic_add(&pool_batch_size, additional_pool_size);
+}
+
+void qemu_coroutine_decrease_pool_batch_size(unsigned int removing_pool_size)
+{
+    qatomic_sub(&pool_batch_size, removing_pool_size);
+}