[Qemu-devel] [RFC PATCH 9/9] pvscsi: implement s/g operation without a bounce buffer

[Paolo Bonzini <pbonzini@redhat.com>]

This implements the new callbacks in the pvscsi device.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/vmw_pvscsi.c |  115 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 114 insertions(+), 1 deletions(-)

diff --git a/hw/vmw_pvscsi.c b/hw/vmw_pvscsi.c
index 1cb6715..ac16e52 100644
--- a/hw/vmw_pvscsi.c
+++ b/hw/vmw_pvscsi.c
@@ -49,6 +49,7 @@ typedef struct {
     QEMUBH *complete_reqs_bh;
 
     int mmio_io_addr;
+    uint32_t use_iovec;
 
     /* zeroed on reset */
     uint32_t cmd_latch;
@@ -387,6 +388,112 @@ static bool pvscsi_check_addresses(PVSCSIRequest *p)
     }
 }
 
+static bool pvscsi_iovec_add(PVSCSIRequest *p, target_phys_addr_t addr,
+                             uint64_t len)
+{
+    while (len) {
+        target_phys_addr_t n = len;
+        uint8_t *buf = cpu_physical_memory_map_fast(addr, &n);
+        if (!buf) {
+            return false;
+        }
+        qemu_iovec_add(&p->sreq->qiov, buf, n);
+        addr += n;
+        len -= n;
+    }
+    return true;
+}
+
+static bool pvscsi_get_sg_list_iovec(PVSCSIRequest *p, uint64_t len)
+{
+    int n;
+    PVSCSISGState sg = p->sg;
+    while (len) {
+        while (!sg.resid) {
+            pvscsi_get_next_sg_elem(&sg);
+            trace_pvscsi_sg_elem(p->req.context, sg.dataAddr, sg.resid);
+        }
+        assert(len > 0);
+        n = MIN((unsigned) len, sg.resid);
+        if (n) {
+            if (!pvscsi_iovec_add(p, sg.dataAddr, n)) {
+	        return false;
+	    }
+        }
+
+        sg.dataAddr += n;
+
+        len -= n;
+        sg.resid -= n;
+    }
+    return true;
+}
+
+static void pvscsi_get_iovec(SCSIRequest *req, uint64_t len)
+{
+    PVSCSIState *s = DO_UPCAST(PVSCSIState, dev.qdev, req->bus->qbus.parent);
+    PVSCSIRequest *p = pvscsi_find_request(s, req);
+    bool ok;
+
+    if (!s->use_iovec) {
+        return;
+    }
+    if (p->req.flags & PVSCSI_FLAG_CMD_WITH_SG_LIST) {
+        ok = pvscsi_get_sg_list_iovec(p, len);
+    } else {
+        ok = pvscsi_iovec_add(p, p->req.dataAddr, MIN(len, p->req.dataLen));
+    }
+    if (!ok) {
+        qemu_iovec_reset(&p->sreq->qiov);
+    }
+}
+
+/* Callback to indicate that the SCSI layer has completed a transfer.  */
+static void pvscsi_unmap_iovec(SCSIRequest *req, uint64_t len)
+{
+    PVSCSIState *s = DO_UPCAST(PVSCSIState, dev.qdev, req->bus->qbus.parent);
+    PVSCSIRequest *p = pvscsi_find_request(s, req);
+    int to_host = (p->req.flags & PVSCSI_FLAG_CMD_DIR_TOHOST) != 0;
+    QEMUIOVector *qiov = &req->qiov;
+    int i;
+
+    if (!p) {
+        fprintf(stderr, "PVSCSI: Can't find request for tag 0x%x\n", req->tag);
+        return;
+    }
+
+    trace_pvscsi_transfer_data(p->req.context, len);
+    if (!len) {
+        /* Short transfer.  */
+        p->cmp.hostStatus = BTSTAT_DATARUN;
+        scsi_req_cancel(req);
+        return;
+    }
+
+    for (i = 0; i < qiov->niov; i++) {
+	uint64_t n = req->qiov.iov[i].iov_len;
+        uint64_t access_len = MIN(len, n);
+	cpu_physical_memory_unmap(req->qiov.iov[i].iov_base, n,
+                                  to_host, access_len);
+
+        if (p->req.flags & PVSCSI_FLAG_CMD_WITH_SG_LIST) {
+            while (!p->sg.resid) {
+                pvscsi_get_next_sg_elem(&p->sg);
+            }
+            assert(n <= p->sg.resid);
+            p->sg.dataAddr += n;
+            p->sg.resid -= n;
+        }
+
+        assert(access_len <= p->resid);
+        p->cmp.dataLen += access_len;
+        p->resid -= access_len;
+        len -= access_len;
+    }
+
+    scsi_req_continue(req);
+}
+
 /* Callback to indicate that the SCSI layer has completed a transfer.  */
 static void pvscsi_transfer_data(SCSIRequest *req, uint32_t len)
 {
@@ -837,7 +944,9 @@ static int pvscsi_uninit(PCIDevice *d)
 static struct SCSIBusOps pvscsi_scsi_ops = {
     .transfer_data = pvscsi_transfer_data,
     .complete = pvscsi_command_complete,
-    .cancel = pvscsi_request_cancelled
+    .cancel = pvscsi_request_cancelled,
+    .get_iovec = pvscsi_get_iovec,
+    .unmap_iovec = pvscsi_unmap_iovec
 };
 
 static int pvscsi_init(PCIDevice *dev)
@@ -891,6 +1000,10 @@ static PCIDeviceInfo pvscsi_info = {
     .qdev.reset = pvscsi_reset,
     .init       = pvscsi_init,
     .exit       = pvscsi_uninit,
+    .qdev.props = (Property[]) {
+        DEFINE_PROP_BIT("sg", PVSCSIState, use_iovec,   0, true),
+        DEFINE_PROP_END_OF_LIST(),
+    },
 };
 
 static void vmw_pvscsi_register_devices(void)
-- 
1.7.4.4