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ipc: add cache flushing and invalidation for IPC data #9630

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Nov 5, 2024
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ipc: add cache flushing and invalidation for IPC data #9630

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1 change: 1 addition & 0 deletions src/include/sof/ipc/msg.h
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@ struct ipc_msg {
uint32_t extension; /* extension specific to platform */
uint32_t tx_size; /* payload size in bytes */
void *tx_data; /* pointer to payload data */
bool is_shared; /* the message is shared cross-core */
struct list_item list;
};

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9 changes: 9 additions & 0 deletions src/ipc/ipc-common.c
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Expand Up @@ -214,6 +214,15 @@ void ipc_msg_send(struct ipc_msg *msg, void *data, bool high_priority)
msg->tx_data != data) {
ret = memcpy_s(msg->tx_data, msg->tx_size, data, msg->tx_size);
assert(!ret);
if (!cpu_is_primary(cpu_get_id())) {
/* Write back data to memory to maintain coherence between cores.
* The response was prepared on a secondary core but will be sent
* to the host from the primary core.
*/
dcache_writeback_region((__sparse_force void __sparse_cache *)msg->tx_data,
msg->tx_size);
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This is a good catch. I wonder if a better fix would be to just allocate tx_data as uncached.

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Possible, but it probably comes with a performance cost. It's hard for me to determine what is better. However, invalidating each message also seems problematic to me, and I considered adding some flag in the structure that would indicate that the payload should be invalidated before copying.

msg->is_shared = true;
}
}

/*
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19 changes: 16 additions & 3 deletions src/ipc/ipc4/handler.c
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Expand Up @@ -72,9 +72,9 @@ struct ipc4_msg_data {
static struct ipc4_msg_data msg_data;

/* fw sends a fw ipc message to send the status of the last host ipc message */
static struct ipc_msg msg_reply = {0, 0, 0, 0, LIST_INIT(msg_reply.list)};
static struct ipc_msg msg_reply = {0, 0, 0, 0, false, LIST_INIT(msg_reply.list)};
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are those static structures ever cleaned? If not, once is_shared is set to true it'll never be set to back false

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Thanks, that was a good catch. It seems to me that I managed to cover all cases now.


static struct ipc_msg msg_notify = {0, 0, 0, 0, LIST_INIT(msg_notify.list)};
static struct ipc_msg msg_notify = {0, 0, 0, 0, false, LIST_INIT(msg_notify.list)};

#if CONFIG_LIBRARY
static inline struct ipc4_message_request *ipc4_get_message_request(void)
Expand Down Expand Up @@ -1494,14 +1494,25 @@ struct ipc_cmd_hdr *ipc_prepare_to_send(const struct ipc_msg *msg)
msg_data.msg_out.pri = msg->header;
msg_data.msg_out.ext = msg->extension;

if (msg->tx_size)
if (msg->tx_size) {
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/* Invalidate cache to ensure we read the latest data from memory.
* The response was prepared on a secondary core but will be sent
* to the host from the primary core.
*/
if (msg->is_shared) {
dcache_invalidate_region((__sparse_force void __sparse_cache *)msg->tx_data,
msg->tx_size);
}

mailbox_dspbox_write(0, (uint32_t *)msg->tx_data, msg->tx_size);
}

/* free memory for get config function */
if (msg == &msg_reply && msg_reply.tx_size > 0) {
rfree(msg_reply.tx_data);
msg_reply.tx_data = NULL;
msg_reply.tx_size = 0;
msg_reply.is_shared = false;
}

return &msg_data.msg_out;
Expand Down Expand Up @@ -1535,6 +1546,7 @@ void ipc_send_panic_notification(void)
{
msg_notify.header = SOF_IPC4_NOTIF_HEADER(SOF_IPC4_EXCEPTION_CAUGHT);
msg_notify.extension = cpu_get_id();
msg_notify.is_shared = !cpu_is_primary(cpu_get_id());
msg_notify.tx_size = 0;
msg_notify.tx_data = NULL;
list_init(&msg_notify.list);
Expand Down Expand Up @@ -1567,6 +1579,7 @@ void ipc_send_buffer_status_notify(void)
msg_notify.header = SOF_IPC4_NOTIF_HEADER(SOF_IPC4_NOTIFY_LOG_BUFFER_STATUS);
msg_notify.extension = 0;
msg_notify.tx_size = 0;
msg_notify.is_shared = false;

tr_dbg(&ipc_tr, "tx-notify\t: %#x|%#x", msg_notify.header, msg_notify.extension);

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1 change: 1 addition & 0 deletions src/library_manager/lib_notification.c
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Expand Up @@ -73,6 +73,7 @@ struct ipc_msg *lib_notif_msg_init(uint32_t header, uint32_t size)
/* Update header and size, since message handle can be reused */
msg->header = header;
msg->tx_size = size;
msg->is_shared = !cpu_is_primary(cpu_get_id());
return msg;
}

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