diff options
Diffstat (limited to 'sys/dev/hyperv/vmbus/hv_ring_buffer.c')
| -rw-r--r-- | sys/dev/hyperv/vmbus/hv_ring_buffer.c | 78 |
1 files changed, 75 insertions, 3 deletions
diff --git a/sys/dev/hyperv/vmbus/hv_ring_buffer.c b/sys/dev/hyperv/vmbus/hv_ring_buffer.c index f7c1965..0e51ef7 100644 --- a/sys/dev/hyperv/vmbus/hv_ring_buffer.c +++ b/sys/dev/hyperv/vmbus/hv_ring_buffer.c @@ -26,6 +26,8 @@ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); #include <sys/param.h> #include <sys/lock.h> @@ -144,6 +146,69 @@ get_ring_buffer_indices(hv_vmbus_ring_buffer_info* ring_info) return (uint64_t) ring_info->ring_buffer->write_index << 32; } +void +hv_ring_buffer_read_begin( + hv_vmbus_ring_buffer_info* ring_info) +{ + ring_info->ring_buffer->interrupt_mask = 1; + mb(); +} + +uint32_t +hv_ring_buffer_read_end( + hv_vmbus_ring_buffer_info* ring_info) +{ + uint32_t read, write; + + ring_info->ring_buffer->interrupt_mask = 0; + mb(); + + /* + * Now check to see if the ring buffer is still empty. + * If it is not, we raced and we need to process new + * incoming messages. + */ + get_ring_buffer_avail_bytes(ring_info, &read, &write); + + return (read); +} + +/* + * When we write to the ring buffer, check if the host needs to + * be signaled. Here is the details of this protocol: + * + * 1. The host guarantees that while it is draining the + * ring buffer, it will set the interrupt_mask to + * indicate it does not need to be interrupted when + * new data is placed. + * + * 2. The host guarantees that it will completely drain + * the ring buffer before exiting the read loop. Further, + * once the ring buffer is empty, it will clear the + * interrupt_mask and re-check to see if new data has + * arrived. + */ +static boolean_t +hv_ring_buffer_needsig_on_write( + uint32_t old_write_location, + hv_vmbus_ring_buffer_info* rbi) +{ + mb(); + if (rbi->ring_buffer->interrupt_mask) + return (FALSE); + + /* Read memory barrier */ + rmb(); + /* + * This is the only case we need to signal when the + * ring transitions from being empty to non-empty. + */ + if (old_write_location == rbi->ring_buffer->read_index) + return (TRUE); + + return (FALSE); +} + static uint32_t copy_to_ring_buffer( hv_vmbus_ring_buffer_info* ring_info, uint32_t start_write_offset, @@ -204,11 +269,13 @@ int hv_ring_buffer_write( hv_vmbus_ring_buffer_info* out_ring_info, hv_vmbus_sg_buffer_list sg_buffers[], - uint32_t sg_buffer_count) + uint32_t sg_buffer_count, + boolean_t *need_sig) { int i = 0; uint32_t byte_avail_to_write; uint32_t byte_avail_to_read; + uint32_t old_write_location; uint32_t total_bytes_to_write = 0; volatile uint32_t next_write_location; @@ -242,6 +309,8 @@ hv_ring_buffer_write( */ next_write_location = get_next_write_location(out_ring_info); + old_write_location = next_write_location; + for (i = 0; i < sg_buffer_count; i++) { next_write_location = copy_to_ring_buffer(out_ring_info, next_write_location, (char *) sg_buffers[i].data, @@ -258,9 +327,9 @@ hv_ring_buffer_write( (char *) &prev_indices, sizeof(uint64_t)); /* - * Make sure we flush all writes before updating the writeIndex + * Full memory barrier before upding the write index. */ - wmb(); + mb(); /* * Now, update the write location @@ -269,6 +338,9 @@ hv_ring_buffer_write( mtx_unlock_spin(&out_ring_info->ring_lock); + *need_sig = hv_ring_buffer_needsig_on_write(old_write_location, + out_ring_info); + return (0); } |
