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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>
This commit is contained in:
Hannes Reinecke 2014-10-29 13:00:15 +01:00 committed by Paolo Bonzini
parent aaf2a859b6
commit 6df5718bd3
2 changed files with 48 additions and 54 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

68
hw/scsi/megasas.c
View File

@ -115,7 +115,7 @@ typedef struct MegasasState {
uint64_t producer_pa;
MegasasCmd frames[MEGASAS_MAX_FRAMES];
DECLARE_BITMAP(frame_map, MEGASAS_MAX_FRAMES);
SCSIBus bus;
} MegasasState;
@ -463,34 +463,20 @@ static MegasasCmd *megasas_lookup_frame(MegasasState *s,
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)
{
@ -498,22 +484,32 @@ static MegasasCmd *megasas_enqueue_frame(MegasasState *s,
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);
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 */
if (!cmd) {
trace_megasas_qf_busy(frame);
return NULL;
}
if (!cmd->pa) {
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) {
pci_dma_unmap(pcid, cmd->frame, frame_size_p, 0, 0);
cmd->frame = NULL;
cmd->pa = 0;
megasas_unmap_frame(s, cmd);
}
s->event_count++;
return NULL;
@ -523,7 +519,6 @@ static MegasasCmd *megasas_enqueue_frame(MegasasState *s,
if (!megasas_use_queue64(s)) {
cmd->context &= (uint64_t)0xFFFFFFFF;
}
}
cmd->count = count;
s->busy++;
@ -544,7 +539,6 @@ static void megasas_complete_frame(MegasasState *s, uint64_t context)
/* Decrement busy count */
s->busy--;
if (s->reply_queue_pa) {
/*
* Put command on the reply queue.
@ -590,18 +584,16 @@ static void megasas_complete_frame(MegasasState *s, uint64_t context)
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 @@ static void megasas_command_complete(SCSIRequest *req, uint32_t status,
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 @@ static void megasas_handle_frame(MegasasState *s, uint64_t frame_addr,
} else {
megasas_frame_set_cmd_status(frame_addr, frame_status);
}
megasas_unmap_frame(s, cmd);
megasas_complete_frame(s, cmd->context);
}
}

6
trace-events
View File

@ -699,9 +699,9 @@ megasas_init_queue(uint64_t queue_pa, int queue_len, uint64_t head, uint64_t tai
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"