megasas: Rework frame queueing algorithm
Windows requires the frames to be unmapped, otherwise we run
into a race condition where the updated frame data is not
visible to the guest.
With that we can simplify the queue algorithm and use a bitmap
for tracking free frames.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/hw/scsi/megasas.c b/hw/scsi/megasas.c
index 3107445..c0d8215 100644
--- a/hw/scsi/megasas.c
+++ b/hw/scsi/megasas.c
@@ -115,7 +115,7 @@
uint64_t producer_pa;
MegasasCmd frames[MEGASAS_MAX_FRAMES];
-
+ DECLARE_BITMAP(frame_map, MEGASAS_MAX_FRAMES);
SCSIBus bus;
} MegasasState;
@@ -463,34 +463,20 @@
return cmd;
}
-static MegasasCmd *megasas_next_frame(MegasasState *s,
- hwaddr frame)
+static void megasas_unmap_frame(MegasasState *s, MegasasCmd *cmd)
{
- MegasasCmd *cmd = NULL;
- int num = 0, index;
+ PCIDevice *p = PCI_DEVICE(s);
- cmd = megasas_lookup_frame(s, frame);
- if (cmd) {
- trace_megasas_qf_found(cmd->index, cmd->pa);
- return cmd;
- }
- index = s->reply_queue_head;
- num = 0;
- while (num < s->fw_cmds) {
- if (!s->frames[index].pa) {
- cmd = &s->frames[index];
- break;
- }
- index = megasas_next_index(s, index, s->fw_cmds);
- num++;
- }
- if (!cmd) {
- trace_megasas_qf_failed(frame);
- }
- trace_megasas_qf_new(index, cmd);
- return cmd;
+ pci_dma_unmap(p, cmd->frame, cmd->pa_size, 0, 0);
+ cmd->frame = NULL;
+ cmd->pa = 0;
+ clear_bit(cmd->index, s->frame_map);
}
+/*
+ * This absolutely needs to be locked if
+ * qemu ever goes multithreaded.
+ */
static MegasasCmd *megasas_enqueue_frame(MegasasState *s,
hwaddr frame, uint64_t context, int count)
{
@@ -498,31 +484,40 @@
MegasasCmd *cmd = NULL;
int frame_size = MFI_FRAME_SIZE * 16;
hwaddr frame_size_p = frame_size;
+ unsigned long index;
- cmd = megasas_next_frame(s, frame);
- /* All frames busy */
- if (!cmd) {
+ index = 0;
+ while (index < s->fw_cmds) {
+ index = find_next_zero_bit(s->frame_map, s->fw_cmds, index);
+ if (!s->frames[index].pa)
+ break;
+ /* Busy frame found */
+ trace_megasas_qf_mapped(index);
+ }
+ if (index >= s->fw_cmds) {
+ /* All frames busy */
+ trace_megasas_qf_busy(frame);
return NULL;
}
- if (!cmd->pa) {
- cmd->pa = frame;
- /* Map all possible frames */
- cmd->frame = pci_dma_map(pcid, frame, &frame_size_p, 0);
- if (frame_size_p != frame_size) {
- trace_megasas_qf_map_failed(cmd->index, (unsigned long)frame);
- if (cmd->frame) {
- pci_dma_unmap(pcid, cmd->frame, frame_size_p, 0, 0);
- cmd->frame = NULL;
- cmd->pa = 0;
- }
- s->event_count++;
- return NULL;
+ cmd = &s->frames[index];
+ set_bit(index, s->frame_map);
+ trace_megasas_qf_new(index, frame);
+
+ cmd->pa = frame;
+ /* Map all possible frames */
+ cmd->frame = pci_dma_map(pcid, frame, &frame_size_p, 0);
+ if (frame_size_p != frame_size) {
+ trace_megasas_qf_map_failed(cmd->index, (unsigned long)frame);
+ if (cmd->frame) {
+ megasas_unmap_frame(s, cmd);
}
- cmd->pa_size = frame_size_p;
- cmd->context = context;
- if (!megasas_use_queue64(s)) {
- cmd->context &= (uint64_t)0xFFFFFFFF;
- }
+ s->event_count++;
+ return NULL;
+ }
+ cmd->pa_size = frame_size_p;
+ cmd->context = context;
+ if (!megasas_use_queue64(s)) {
+ cmd->context &= (uint64_t)0xFFFFFFFF;
}
cmd->count = count;
s->busy++;
@@ -544,7 +539,6 @@
/* Decrement busy count */
s->busy--;
-
if (s->reply_queue_pa) {
/*
* Put command on the reply queue.
@@ -590,18 +584,16 @@
static void megasas_reset_frames(MegasasState *s)
{
- PCIDevice *pcid = PCI_DEVICE(s);
int i;
MegasasCmd *cmd;
for (i = 0; i < s->fw_cmds; i++) {
cmd = &s->frames[i];
if (cmd->pa) {
- pci_dma_unmap(pcid, cmd->frame, cmd->pa_size, 0, 0);
- cmd->frame = NULL;
- cmd->pa = 0;
+ megasas_unmap_frame(s, cmd);
}
}
+ bitmap_zero(s->frame_map, MEGASAS_MAX_FRAMES);
}
static void megasas_abort_command(MegasasCmd *cmd)
@@ -1894,6 +1886,7 @@
cmd->req = NULL;
}
cmd->frame->header.cmd_status = cmd_status;
+ megasas_unmap_frame(cmd->state, cmd);
megasas_complete_frame(cmd->state, cmd->context);
}
@@ -1997,6 +1990,7 @@
} else {
megasas_frame_set_cmd_status(frame_addr, frame_status);
}
+ megasas_unmap_frame(s, cmd);
megasas_complete_frame(s, cmd->context);
}
}
diff --git a/trace-events b/trace-events
index 3399219..24df190 100644
--- a/trace-events
+++ b/trace-events
@@ -699,9 +699,9 @@
megasas_initq_map_failed(int frame) "scmd %d: failed to map queue"
megasas_initq_mapped(uint64_t pa) "queue already mapped at %" PRIx64 ""
megasas_initq_mismatch(int queue_len, int fw_cmds) "queue size %d max fw cmds %d"
-megasas_qf_found(unsigned int index, uint64_t pa) "mapped frame %x pa %" PRIx64 ""
-megasas_qf_new(unsigned int index, void *cmd) "return new frame %x cmd %p"
-megasas_qf_failed(unsigned long pa) "all frames busy for frame %lx"
+megasas_qf_mapped(unsigned int index) "skip mapped frame %x"
+megasas_qf_new(unsigned int index, uint64_t frame) "frame %x addr %" PRIx64 ""
+megasas_qf_busy(unsigned long pa) "all frames busy for frame %lx"
megasas_qf_enqueue(unsigned int index, unsigned int count, uint64_t context, unsigned int head, unsigned int tail, int busy) "frame %x count %d context %" PRIx64 " head %x tail %x busy %d"
megasas_qf_update(unsigned int head, unsigned int tail, unsigned int busy) "head %x tail %x busy %d"
megasas_qf_map_failed(int cmd, unsigned long frame) "scmd %d: frame %lu"