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Re: [Xen-devel] [RFC PATCH 12/16] xen/xenbus: support xenbus frontend/backend with xenhost_t





On 6/17/19 2:50 AM, Juergen Gross wrote:
On 09.05.19 19:25, Ankur Arora wrote:
As part of xenbus init, both frontend, backend interfaces need to talk
on the correct xenbus. This might be a local xenstore (backend) or might
be a XS_PV/XS_HVM interface (frontend) which needs to talk over xenbus
with the remote xenstored. We bootstrap all of these with evtchn/gfn
parameters from (*setup_xs)().

Given this we can do appropriate device discovery (in case of frontend)
and device connectivity for the backend.
Once done, we stash the xenhost_t * in xen_bus_type, xenbus_device or
xenbus_watch and then the frontend and backend devices implicitly use
the correct interface.

The rest of patch is just changing the interfaces where needed.

Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx>
---
  drivers/block/xen-blkback/blkback.c        |  10 +-
  drivers/net/xen-netfront.c                 |  14 +-
  drivers/pci/xen-pcifront.c                 |   4 +-
  drivers/xen/cpu_hotplug.c                  |   4 +-
  drivers/xen/manage.c                       |  28 +--
  drivers/xen/xen-balloon.c                  |   8 +-
  drivers/xen/xenbus/xenbus.h                |  45 ++--
  drivers/xen/xenbus/xenbus_client.c         |  32 +--
  drivers/xen/xenbus/xenbus_comms.c          | 121 +++++-----
  drivers/xen/xenbus/xenbus_dev_backend.c    |  30 ++-
  drivers/xen/xenbus/xenbus_dev_frontend.c   |  22 +-
  drivers/xen/xenbus/xenbus_probe.c          | 246 +++++++++++++--------
  drivers/xen/xenbus/xenbus_probe_backend.c  |  19 +-
  drivers/xen/xenbus/xenbus_probe_frontend.c |  65 +++---
  drivers/xen/xenbus/xenbus_xs.c             | 188 +++++++++-------
  include/xen/xen-ops.h                      |   3 +
  include/xen/xenbus.h                       |  54 +++--
  include/xen/xenhost.h                      |  20 ++
  18 files changed, 536 insertions(+), 377 deletions(-)

diff --git a/drivers/xen/xenbus/xenbus_dev_frontend.c b/drivers/xen/xenbus/xenbus_dev_frontend.c
index c3e201025ef0..d6e0c397c6a0 100644
--- a/drivers/xen/xenbus/xenbus_dev_frontend.c
+++ b/drivers/xen/xenbus/xenbus_dev_frontend.c
@@ -58,10 +58,14 @@
  #include <xen/xenbus.h>
  #include <xen/xen.h>
+#include <xen/interface/xen.h>
+#include <xen/xenhost.h>
  #include <asm/xen/hypervisor.h>
  #include "xenbus.h"
+static xenhost_t *xh;
+
  /*
   * An element of a list of outstanding transactions, for which we're
   * still waiting a reply.
@@ -312,13 +316,13 @@ static void xenbus_file_free(struct kref *kref)
       */
      list_for_each_entry_safe(trans, tmp, &u->transactions, list) {
-        xenbus_transaction_end(trans->handle, 1);
+        xenbus_transaction_end(xh, trans->handle, 1);
          list_del(&trans->list);
          kfree(trans);
      }
      list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
-        unregister_xenbus_watch(&watch->watch);
+        unregister_xenbus_watch(xh, &watch->watch);
          list_del(&watch->list);
          free_watch_adapter(watch);
      }
@@ -450,7 +454,7 @@ static int xenbus_write_transaction(unsigned msg_type,
             (!strcmp(msg->body, "T") || !strcmp(msg->body, "F"))))
          return xenbus_command_reply(u, XS_ERROR, "EINVAL");
-    rc = xenbus_dev_request_and_reply(&msg->hdr, u);
+    rc = xenbus_dev_request_and_reply(xh, &msg->hdr, u);
      if (rc && trans) {
          list_del(&trans->list);
          kfree(trans);
@@ -489,7 +493,7 @@ static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
          watch->watch.callback = watch_fired;
          watch->dev_data = u;
-        err = register_xenbus_watch(&watch->watch);
+        err = register_xenbus_watch(xh, &watch->watch);
          if (err) {
              free_watch_adapter(watch);
              rc = err;
@@ -500,7 +504,7 @@ static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
          list_for_each_entry(watch, &u->watches, list) {
              if (!strcmp(watch->token, token) &&
                  !strcmp(watch->watch.node, path)) {
-                unregister_xenbus_watch(&watch->watch);
+                unregister_xenbus_watch(xh, &watch->watch);
                  list_del(&watch->list);
                  free_watch_adapter(watch);
                  break;
@@ -618,8 +622,9 @@ static ssize_t xenbus_file_write(struct file *filp,
  static int xenbus_file_open(struct inode *inode, struct file *filp)
  {
      struct xenbus_file_priv *u;
+    struct xenstore_private *xs = xs_priv(xh);
-    if (xen_store_evtchn == 0)
+    if (xs->store_evtchn == 0)
          return -ENOENT;
      nonseekable_open(inode, filp);
@@ -687,6 +692,11 @@ static int __init xenbus_init(void)
      if (!xen_domain())
          return -ENODEV;
+    if (xen_driver_domain() && xen_nested())
+        xh = xh_remote;
+    else
+        xh = xh_default;

This precludes any mixed use of L0 and L1 frontends. With this move you
make it impossible to e.g. use a driver domain for networking in L1 with
a L1-local PV disk, or pygrub in L1 dom0.
Ah, yes. I hadn't thought about that case.

Let me see how I can rework this interface.

Ankur



Juergen

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