Author: mav
Date: Thu Aug 15 22:55:59 2019
New Revision: 351105
URL: https://svnweb.freebsd.org/changeset/base/351105

Log:
  Limit memory window usage in ntb_transport to 256MB.
  
  This adds safety net for the case of misconfigured NTB with too big
  memory window, for which we may be unable to allocate a memory buffer,
  which does not make much sense for the network interface.  While there,
  fix the code to really work with asymmetric window sizes setup.
  
  This makes driver just print warning message on boot instead of hanging
  if too large memory window is configured.
  
  MFC after:    2 weeks
  Sponsored by: iXsystems, Inc.

Modified:
  head/share/man/man4/ntb_transport.4
  head/sys/dev/ntb/ntb_transport.c

Modified: head/share/man/man4/ntb_transport.4
==============================================================================
--- head/share/man/man4/ntb_transport.4 Thu Aug 15 21:51:11 2019        
(r351104)
+++ head/share/man/man4/ntb_transport.4 Thu Aug 15 22:55:59 2019        
(r351105)
@@ -1,5 +1,5 @@
 .\"
-.\" Copyright (c) 2016-2017 Alexander Motin <m...@freebsd.org>
+.\" Copyright (c) 2016-2019 Alexander Motin <m...@freebsd.org>
 .\" All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd September 2, 2017
+.Dd August 15, 2019
 .Dt NTB_TRANSPORT 4
 .Os
 .Sh NAME
@@ -51,6 +51,10 @@ The following tunables are settable from the
 .It Va hw.ntb_transport.debug_level
 Driver debug level.
 The default value is 0, higher means more verbose.
+.It Va hw.ntb_transport.max_mw_size
+Limits maximum memory window usage.
+Allocation of big physically contiguous memory buffer may be a problem,
+while too big buffers makes no much sense for low latency network interface.
 .It Va hint.ntb_transport. Ns Ar X Ns Va .config
 Configures a set of the transport consumers, separated by commas.
 Each consumer can be configured as: "[<name>][:<queues>]", where:

Modified: head/sys/dev/ntb/ntb_transport.c
==============================================================================
--- head/sys/dev/ntb/ntb_transport.c    Thu Aug 15 21:51:11 2019        
(r351104)
+++ head/sys/dev/ntb/ntb_transport.c    Thu Aug 15 22:55:59 2019        
(r351105)
@@ -81,7 +81,7 @@ SYSCTL_UINT(_hw_ntb_transport, OID_AUTO, debug_level, 
 
 static unsigned transport_mtu = 0x10000;
 
-static uint64_t max_mw_size;
+static uint64_t max_mw_size = 256*1024*1024;
 SYSCTL_UQUAD(_hw_ntb_transport, OID_AUTO, max_mw_size, CTLFLAG_RDTUN, 
&max_mw_size, 0,
     "If enabled (non-zero), limit the size of large memory windows. "
     "Both sides of the NTB MUST set the same value here.");
@@ -177,14 +177,17 @@ struct ntb_transport_mw {
        size_t          xlat_align;
        size_t          xlat_align_size;
        bus_addr_t      addr_limit;
-       /* Tx buff is off vbase / phys_addr */
+       /* Tx buff is vbase / phys_addr / tx_size */
        caddr_t         vbase;
-       size_t          buff_size;
-       /* Rx buff is off virt_addr / dma_addr */
+       size_t          tx_size;
+       /* Rx buff is virt_addr / dma_addr / rx_size */
        bus_dma_tag_t   dma_tag;
        bus_dmamap_t    dma_map;
        caddr_t         virt_addr;
        bus_addr_t      dma_addr;
+       size_t          rx_size;
+       /* rx_size increased to size alignment requirements of the hardware. */
+       size_t          buff_size;
 };
 
 struct ntb_transport_child {
@@ -331,7 +334,7 @@ ntb_transport_attach(device_t dev)
        struct ntb_transport_child **cpp = &nt->child;
        struct ntb_transport_child *nc;
        struct ntb_transport_mw *mw;
-       uint64_t db_bitmap, size;
+       uint64_t db_bitmap;
        int rc, i, db_count, spad_count, qp, qpu, qpo, qpt;
        char cfg[128] = "";
        char buf[32];
@@ -374,6 +377,14 @@ ntb_transport_attach(device_t dev)
                if (rc != 0)
                        goto err;
 
+               mw->tx_size = mw->phys_size;
+               if (max_mw_size != 0 && mw->tx_size > max_mw_size) {
+                       device_printf(dev, "Memory window %d limited from "
+                           "%ju to %ju\n", i, mw->phys_size, max_mw_size);
+                       mw->tx_size = max_mw_size;
+               }
+
+               mw->rx_size = 0;
                mw->buff_size = 0;
                mw->virt_addr = NULL;
                mw->dma_addr = 0;
@@ -388,10 +399,7 @@ ntb_transport_attach(device_t dev)
                 * that NTB windows are symmetric and this allocation remain,
                 * but even if not, we will just reallocate it later.
                 */
-               size = mw->phys_size;
-               if (max_mw_size != 0 && size > max_mw_size)
-                       size = max_mw_size;
-               ntb_set_mw(nt, i, size);
+               ntb_set_mw(nt, i, mw->tx_size);
        }
 
        qpu = 0;
@@ -556,7 +564,7 @@ ntb_transport_init_queue(struct ntb_transport_ctx *nt,
        struct ntb_transport_mw *mw;
        struct ntb_transport_qp *qp;
        vm_paddr_t mw_base;
-       uint64_t mw_size, qp_offset;
+       uint64_t qp_offset;
        size_t tx_size;
        unsigned num_qps_mw, mw_num, mw_count;
 
@@ -578,9 +586,8 @@ ntb_transport_init_queue(struct ntb_transport_ctx *nt,
                num_qps_mw = nt->qp_count / mw_count;
 
        mw_base = mw->phys_addr;
-       mw_size = mw->phys_size;
 
-       tx_size = mw_size / num_qps_mw;
+       tx_size = mw->tx_size / num_qps_mw;
        qp_offset = tx_size * (qp_num / mw_count);
 
        qp->tx_mw = mw->vbase + qp_offset;
@@ -1103,11 +1110,7 @@ ntb_transport_link_work(void *arg)
 
        /* send the local info, in the opposite order of the way we read it */
        for (i = 0; i < nt->mw_count; i++) {
-               size = nt->mw_vec[i].phys_size;
-
-               if (max_mw_size != 0 && size > max_mw_size)
-                       size = max_mw_size;
-
+               size = nt->mw_vec[i].tx_size;
                ntb_peer_spad_write(dev, NTBT_MW0_SZ_HIGH + (i * 2),
                    size >> 32);
                ntb_peer_spad_write(dev, NTBT_MW0_SZ_LOW + (i * 2), size);
@@ -1139,6 +1142,7 @@ ntb_transport_link_work(void *arg)
                val64 |= val;
 
                mw = &nt->mw_vec[i];
+               mw->rx_size = val64;
                val64 = roundup(val64, mw->xlat_align_size);
                if (mw->buff_size != val64) {
 
@@ -1288,7 +1292,7 @@ ntb_transport_setup_qp_mw(struct ntb_transport_ctx *nt
        else
                num_qps_mw = nt->qp_count / mw_count;
 
-       rx_size = mw->buff_size / num_qps_mw;
+       rx_size = mw->rx_size / num_qps_mw;
        qp->rx_buff = mw->virt_addr + rx_size * (qp_num / mw_count);
        rx_size -= sizeof(struct ntb_rx_info);
 
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