pvrdma: wean code off pvrdma_ring.h kernel header

The pvrdma code relies on the pvrdma_ring.h kernel header for some
basic ring buffer handling. The content of that header isn't very
exciting, but contains some (q)atomic_*() invocations that (a)
cause manual massaging when doing a headers update, and (b) are
an indication that we probably should not be importing that header
at all.

Let's reimplement the ring buffer handling directly in the pvrdma
code instead. This arguably also improves readability of the code.

Importing the header can now be dropped.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Yuval Shaia <yuval.shaia.ml@gmail.com>
Tested-by: Yuval Shaia <yuval.shaia.ml@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

5 files changed, 37 insertions, 28 deletions

diff --git a/hw/rdma/vmw/pvrdma.h b/hw/rdma/vmw/pvrdma.h
index 1d36a76..d08965d 100644
--- a/hw/rdma/vmw/pvrdma.h
+++ b/hw/rdma/vmw/pvrdma.h
@@ -26,7 +26,6 @@
 #include "../rdma_backend_defs.h"
 #include "../rdma_rm_defs.h"
 
-#include "standard-headers/drivers/infiniband/hw/vmw_pvrdma/pvrdma_ring.h"
 #include "standard-headers/drivers/infiniband/hw/vmw_pvrdma/pvrdma_dev_api.h"
 #include "pvrdma_dev_ring.h"
 #include "qom/object.h"
@@ -64,10 +63,10 @@ typedef struct DSRInfo {
     union pvrdma_cmd_req *req;
     union pvrdma_cmd_resp *rsp;
 
-    struct pvrdma_ring *async_ring_state;
+    PvrdmaRingState *async_ring_state;
     PvrdmaRing async;
 
-    struct pvrdma_ring *cq_ring_state;
+    PvrdmaRingState *cq_ring_state;
     PvrdmaRing cq;
 } DSRInfo;
 
diff --git a/hw/rdma/vmw/pvrdma_cmd.c b/hw/rdma/vmw/pvrdma_cmd.c
index 692125a..f59879e 100644
--- a/hw/rdma/vmw/pvrdma_cmd.c
+++ b/hw/rdma/vmw/pvrdma_cmd.c
@@ -262,7 +262,7 @@ static int create_cq_ring(PCIDevice *pci_dev , PvrdmaRing **ring,
     r = g_malloc(sizeof(*r));
     *ring = r;
 
-    r->ring_state = (struct pvrdma_ring *)
+    r->ring_state = (PvrdmaRingState *)
         rdma_pci_dma_map(pci_dev, tbl[0], TARGET_PAGE_SIZE);
 
     if (!r->ring_state) {
@@ -398,7 +398,7 @@ static int create_qp_rings(PCIDevice *pci_dev, uint64_t pdir_dma,
     *rings = sr;
 
     /* Create send ring */
-    sr->ring_state = (struct pvrdma_ring *)
+    sr->ring_state = (PvrdmaRingState *)
         rdma_pci_dma_map(pci_dev, tbl[0], TARGET_PAGE_SIZE);
     if (!sr->ring_state) {
         rdma_error_report("Failed to map to QP ring state");
@@ -639,7 +639,7 @@ static int create_srq_ring(PCIDevice *pci_dev, PvrdmaRing **ring,
     r = g_malloc(sizeof(*r));
     *ring = r;
 
-    r->ring_state = (struct pvrdma_ring *)
+    r->ring_state = (PvrdmaRingState *)
             rdma_pci_dma_map(pci_dev, tbl[0], TARGET_PAGE_SIZE);
     if (!r->ring_state) {
         rdma_error_report("Failed to map tp SRQ ring state");
diff --git a/hw/rdma/vmw/pvrdma_dev_ring.c b/hw/rdma/vmw/pvrdma_dev_ring.c
index f0bcde7..074ac59 100644
--- a/hw/rdma/vmw/pvrdma_dev_ring.c
+++ b/hw/rdma/vmw/pvrdma_dev_ring.c
@@ -22,11 +22,10 @@
 #include "trace.h"
 
 #include "../rdma_utils.h"
-#include "standard-headers/drivers/infiniband/hw/vmw_pvrdma/pvrdma_ring.h"
 #include "pvrdma_dev_ring.h"
 
 int pvrdma_ring_init(PvrdmaRing *ring, const char *name, PCIDevice *dev,
-                     struct pvrdma_ring *ring_state, uint32_t max_elems,
+                     PvrdmaRingState *ring_state, uint32_t max_elems,
                      size_t elem_sz, dma_addr_t *tbl, uint32_t npages)
 {
     int i;
@@ -73,48 +72,54 @@ out:
 
 void *pvrdma_ring_next_elem_read(PvrdmaRing *ring)
 {
-    int e;
-    unsigned int idx = 0, offset;
+    unsigned int idx, offset;
+    const uint32_t tail = qatomic_read(&ring->ring_state->prod_tail);
+    const uint32_t head = qatomic_read(&ring->ring_state->cons_head);
 
-    e = pvrdma_idx_ring_has_data(ring->ring_state, ring->max_elems, &idx);
-    if (e <= 0) {
+    if (tail & ~((ring->max_elems << 1) - 1) ||
+        head & ~((ring->max_elems << 1) - 1) ||
+        tail == head) {
         trace_pvrdma_ring_next_elem_read_no_data(ring->name);
         return NULL;
     }
 
+    idx = head & (ring->max_elems - 1);
     offset = idx * ring->elem_sz;
     return ring->pages[offset / TARGET_PAGE_SIZE] + (offset % TARGET_PAGE_SIZE);
 }
 
 void pvrdma_ring_read_inc(PvrdmaRing *ring)
 {
-    pvrdma_idx_ring_inc(&ring->ring_state->cons_head, ring->max_elems);
+    uint32_t idx = qatomic_read(&ring->ring_state->cons_head);
+
+    idx = (idx + 1) & ((ring->max_elems << 1) - 1);
+    qatomic_set(&ring->ring_state->cons_head, idx);
 }
 
 void *pvrdma_ring_next_elem_write(PvrdmaRing *ring)
 {
-    int idx;
-    unsigned int offset, tail;
+    unsigned int idx, offset;
+    const uint32_t tail = qatomic_read(&ring->ring_state->prod_tail);
+    const uint32_t head = qatomic_read(&ring->ring_state->cons_head);
 
-    idx = pvrdma_idx_ring_has_space(ring->ring_state, ring->max_elems, &tail);
-    if (idx <= 0) {
+    if (tail & ~((ring->max_elems << 1) - 1) ||
+        head & ~((ring->max_elems << 1) - 1) ||
+        tail == (head ^ ring->max_elems)) {
         rdma_error_report("CQ is full");
         return NULL;
     }
 
-    idx = pvrdma_idx(&ring->ring_state->prod_tail, ring->max_elems);
-    if (idx < 0 || tail != idx) {
-        rdma_error_report("Invalid idx %d", idx);
-        return NULL;
-    }
-
+    idx = tail & (ring->max_elems - 1);
     offset = idx * ring->elem_sz;
     return ring->pages[offset / TARGET_PAGE_SIZE] + (offset % TARGET_PAGE_SIZE);
 }
 
 void pvrdma_ring_write_inc(PvrdmaRing *ring)
 {
-    pvrdma_idx_ring_inc(&ring->ring_state->prod_tail, ring->max_elems);
+    uint32_t idx = qatomic_read(&ring->ring_state->prod_tail);
+
+    idx = (idx + 1) & ((ring->max_elems << 1) - 1);
+    qatomic_set(&ring->ring_state->prod_tail, idx);
 }
 
 void pvrdma_ring_free(PvrdmaRing *ring)
diff --git a/hw/rdma/vmw/pvrdma_dev_ring.h b/hw/rdma/vmw/pvrdma_dev_ring.h
index 5f2a0cf..d231588 100644
--- a/hw/rdma/vmw/pvrdma_dev_ring.h
+++ b/hw/rdma/vmw/pvrdma_dev_ring.h
@@ -19,18 +19,23 @@
 
 #define MAX_RING_NAME_SZ 32
 
+typedef struct PvrdmaRingState {
+    int prod_tail; /* producer tail */
+    int cons_head; /* consumer head */
+} PvrdmaRingState;
+
 typedef struct PvrdmaRing {
     char name[MAX_RING_NAME_SZ];
     PCIDevice *dev;
     uint32_t max_elems;
     size_t elem_sz;
-    struct pvrdma_ring *ring_state; /* used only for unmap */
+    PvrdmaRingState *ring_state; /* used only for unmap */
     int npages;
     void **pages;
 } PvrdmaRing;
 
 int pvrdma_ring_init(PvrdmaRing *ring, const char *name, PCIDevice *dev,
-                     struct pvrdma_ring *ring_state, uint32_t max_elems,
+                     PvrdmaRingState *ring_state, uint32_t max_elems,
                      size_t elem_sz, dma_addr_t *tbl, uint32_t npages);
 void *pvrdma_ring_next_elem_read(PvrdmaRing *ring);
 void pvrdma_ring_read_inc(PvrdmaRing *ring);
diff --git a/hw/rdma/vmw/pvrdma_main.c b/hw/rdma/vmw/pvrdma_main.c
index 8593570..84ae802 100644
--- a/hw/rdma/vmw/pvrdma_main.c
+++ b/hw/rdma/vmw/pvrdma_main.c
@@ -85,7 +85,7 @@ static void free_dev_ring(PCIDevice *pci_dev, PvrdmaRing *ring,
     rdma_pci_dma_unmap(pci_dev, ring_state, TARGET_PAGE_SIZE);
 }
 
-static int init_dev_ring(PvrdmaRing *ring, struct pvrdma_ring **ring_state,
+static int init_dev_ring(PvrdmaRing *ring, PvrdmaRingState **ring_state,
                          const char *name, PCIDevice *pci_dev,
                          dma_addr_t dir_addr, uint32_t num_pages)
 {
@@ -114,7 +114,7 @@ static int init_dev_ring(PvrdmaRing *ring, struct pvrdma_ring **ring_state,
     /* RX ring is the second */
     (*ring_state)++;
     rc = pvrdma_ring_init(ring, name, pci_dev,
-                          (struct pvrdma_ring *)*ring_state,
+                          (PvrdmaRingState *)*ring_state,
                           (num_pages - 1) * TARGET_PAGE_SIZE /
                           sizeof(struct pvrdma_cqne),
                           sizeof(struct pvrdma_cqne),