qemu/system-physmem-Per-AddressSpace-bounce-buffering.patch

From dcab52cf7a81db32d744aae81888a3ed1d3a9efa Mon Sep 17 00:00:00 2001
From: Mattias Nissler <mnissler@rivosinc.com>
Date: Thu, 7 Sep 2023 06:04:23 -0700
Subject: [PATCH] system/physmem: Per-AddressSpace bounce buffering
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cherry-pick 69e78f1b3484e429274352a464a94fa1d78be339

Instead of using a single global bounce buffer, give each AddressSpace
its own bounce buffer. The MapClient callback mechanism moves to
AddressSpace accordingly.

This is in preparation for generalizing bounce buffer handling further
to allow multiple bounce buffers, with a total allocation limit
configured per AddressSpace.

Reviewed-by: Peter Xu <peterx@redhat.com>
Tested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Mattias Nissler <mnissler@rivosinc.com>
Message-ID: <20240507094210.300566-2-mnissler@rivosinc.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
[PMD: Split patch, part 2/2]
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/exec/memory.h | 19 +++++++++++
 softmmu/memory.c      |  7 ++++
 softmmu/physmem.c     | 79 ++++++++++++++++---------------------------
 3 files changed, 56 insertions(+), 49 deletions(-)

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 859e3da182..f6bde44ecf 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -1035,6 +1035,19 @@ struct MemoryListener {
     QTAILQ_ENTRY(MemoryListener) link_as;
 };
 
+typedef struct AddressSpaceMapClient {
+    QEMUBH *bh;
+    QLIST_ENTRY(AddressSpaceMapClient) link;
+} AddressSpaceMapClient;
+
+typedef struct {
+    MemoryRegion *mr;
+    void *buffer;
+    hwaddr addr;
+    hwaddr len;
+    bool in_use;
+} BounceBuffer;
+
 /**
  * struct AddressSpace: describes a mapping of addresses to #MemoryRegion objects
  */
@@ -1051,6 +1064,12 @@ struct AddressSpace {
     struct MemoryRegionIoeventfd *ioeventfds;
     QTAILQ_HEAD(, MemoryListener) listeners;
     QTAILQ_ENTRY(AddressSpace) address_spaces_link;
+
+    /* Bounce buffer to use for this address space. */
+    BounceBuffer bounce;
+    /* List of callbacks to invoke when buffers free up */
+    QemuMutex map_client_list_lock;
+    QLIST_HEAD(, AddressSpaceMapClient) map_client_list;
 };
 
 typedef struct AddressSpaceDispatch AddressSpaceDispatch;
diff --git a/softmmu/memory.c b/softmmu/memory.c
index 0bf37f11aa..3ab6a58902 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -2946,6 +2946,9 @@ void address_space_init(AddressSpace *as, MemoryRegion *root, const char *name)
     as->ioeventfds = NULL;
     QTAILQ_INIT(&as->listeners);
     QTAILQ_INSERT_TAIL(&address_spaces, as, address_spaces_link);
+    as->bounce.in_use = false;
+    qemu_mutex_init(&as->map_client_list_lock);
+    QLIST_INIT(&as->map_client_list);
     as->name = g_strdup(name ? name : "anonymous");
     address_space_update_topology(as);
     address_space_update_ioeventfds(as);
@@ -2953,6 +2956,10 @@ void address_space_init(AddressSpace *as, MemoryRegion *root, const char *name)
 
 static void do_address_space_destroy(AddressSpace *as)
 {
+    assert(!qatomic_read(&as->bounce.in_use));
+    assert(QLIST_EMPTY(&as->map_client_list));
+    qemu_mutex_destroy(&as->map_client_list_lock);
+
     assert(QTAILQ_EMPTY(&as->listeners));
 
     flatview_unref(as->current_map);
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index b86d7a0cf4..9905d55c67 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -3081,26 +3081,8 @@ void cpu_flush_icache_range(hwaddr start, hwaddr len)
                                      NULL, len, FLUSH_CACHE);
 }
 
-typedef struct {
-    MemoryRegion *mr;
-    void *buffer;
-    hwaddr addr;
-    hwaddr len;
-    bool in_use;
-} BounceBuffer;
-
-static BounceBuffer bounce;
-
-typedef struct MapClient {
-    QEMUBH *bh;
-    QLIST_ENTRY(MapClient) link;
-} MapClient;
-
-QemuMutex map_client_list_lock;
-static QLIST_HEAD(, MapClient) map_client_list
-    = QLIST_HEAD_INITIALIZER(map_client_list);
-
-static void address_space_unregister_map_client_do(MapClient *client)
+static void
+address_space_unregister_map_client_do(AddressSpaceMapClient *client)
 {
     QLIST_REMOVE(client, link);
     g_free(client);
@@ -3108,10 +3090,10 @@ static void address_space_unregister_map_client_do(MapClient *client)
 
 static void address_space_notify_map_clients_locked(AddressSpace *as)
 {
-    MapClient *client;
+    AddressSpaceMapClient *client;
 
-    while (!QLIST_EMPTY(&map_client_list)) {
-        client = QLIST_FIRST(&map_client_list);
+    while (!QLIST_EMPTY(&as->map_client_list)) {
+        client = QLIST_FIRST(&as->map_client_list);
         qemu_bh_schedule(client->bh);
         address_space_unregister_map_client_do(client);
     }
@@ -3119,15 +3101,15 @@ static void address_space_notify_map_clients_locked(AddressSpace *as)
 
 void address_space_register_map_client(AddressSpace *as, QEMUBH *bh)
 {
-    MapClient *client = g_malloc(sizeof(*client));
+    AddressSpaceMapClient *client = g_malloc(sizeof(*client));
 
-    qemu_mutex_lock(&map_client_list_lock);
+    qemu_mutex_lock(&as->map_client_list_lock);
     client->bh = bh;
-    QLIST_INSERT_HEAD(&map_client_list, client, link);
-    if (!qatomic_read(&bounce.in_use)) {
+    QLIST_INSERT_HEAD(&as->map_client_list, client, link);
+    if (!qatomic_read(&as->bounce.in_use)) {
         address_space_notify_map_clients_locked(as);
     }
-    qemu_mutex_unlock(&map_client_list_lock);
+    qemu_mutex_unlock(&as->map_client_list_lock);
 }
 
 void cpu_exec_init_all(void)
@@ -3143,28 +3125,27 @@ void cpu_exec_init_all(void)
     finalize_target_page_bits();
     io_mem_init();
     memory_map_init();
-    qemu_mutex_init(&map_client_list_lock);
 }
 
 void address_space_unregister_map_client(AddressSpace *as, QEMUBH *bh)
 {
-    MapClient *client;
+    AddressSpaceMapClient *client;
 
-    qemu_mutex_lock(&map_client_list_lock);
-    QLIST_FOREACH(client, &map_client_list, link) {
+    qemu_mutex_lock(&as->map_client_list_lock);
+    QLIST_FOREACH(client, &as->map_client_list, link) {
         if (client->bh == bh) {
             address_space_unregister_map_client_do(client);
             break;
         }
     }
-    qemu_mutex_unlock(&map_client_list_lock);
+    qemu_mutex_unlock(&as->map_client_list_lock);
 }
 
 static void address_space_notify_map_clients(AddressSpace *as)
 {
-    qemu_mutex_lock(&map_client_list_lock);
+    qemu_mutex_lock(&as->map_client_list_lock);
     address_space_notify_map_clients_locked(as);
-    qemu_mutex_unlock(&map_client_list_lock);
+    qemu_mutex_unlock(&as->map_client_list_lock);
 }
 
 static bool flatview_access_valid(FlatView *fv, hwaddr addr, hwaddr len,
@@ -3256,25 +3237,25 @@ void *address_space_map(AddressSpace *as,
     mr = flatview_translate(fv, addr, &xlat, &l, is_write, attrs);
 
     if (!memory_access_is_direct(mr, is_write)) {
-        if (qatomic_xchg(&bounce.in_use, true)) {
+        if (qatomic_xchg(&as->bounce.in_use, true)) {
             *plen = 0;
             return NULL;
         }
         /* Avoid unbounded allocations */
         l = MIN(l, TARGET_PAGE_SIZE);
-        bounce.buffer = qemu_memalign(TARGET_PAGE_SIZE, l);
-        bounce.addr = addr;
-        bounce.len = l;
+        as->bounce.buffer = qemu_memalign(TARGET_PAGE_SIZE, l);
+        as->bounce.addr = addr;
+        as->bounce.len = l;
 
         memory_region_ref(mr);
-        bounce.mr = mr;
+        as->bounce.mr = mr;
         if (!is_write) {
             flatview_read(fv, addr, MEMTXATTRS_UNSPECIFIED,
-                               bounce.buffer, l);
+                          as->bounce.buffer, l);
         }
 
         *plen = l;
-        return bounce.buffer;
+        return as->bounce.buffer;
     }
 
 
@@ -3294,7 +3275,7 @@ void *address_space_map(AddressSpace *as,
 void address_space_unmap(AddressSpace *as, void *buffer, hwaddr len,
                          bool is_write, hwaddr access_len)
 {
-    if (buffer != bounce.buffer) {
+    if (buffer != as->bounce.buffer) {
         MemoryRegion *mr;
         ram_addr_t addr1;
 
@@ -3310,13 +3291,13 @@ void address_space_unmap(AddressSpace *as, void *buffer, hwaddr len,
         return;
     }
     if (is_write) {
-        address_space_write(as, bounce.addr, MEMTXATTRS_UNSPECIFIED,
-                            bounce.buffer, access_len);
+        address_space_write(as, as->bounce.addr, MEMTXATTRS_UNSPECIFIED,
+                            as->bounce.buffer, access_len);
     }
-    qemu_vfree(bounce.buffer);
-    bounce.buffer = NULL;
-    memory_region_unref(bounce.mr);
-    qatomic_mb_set(&bounce.in_use, false);
+    qemu_vfree(as->bounce.buffer);
+    as->bounce.buffer = NULL;
+    memory_region_unref(as->bounce.mr);
+    qatomic_mb_set(&as->bounce.in_use, false);
     address_space_notify_map_clients(as);
 }
 
-- 
2.45.1.windows.1