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Re: [PATCH v12 13/19] multi-process: add proxy communication functions


From: Marc-André Lureau
Subject: Re: [PATCH v12 13/19] multi-process: add proxy communication functions
Date: Tue, 8 Dec 2020 16:39:03 +0400

Hi

On Wed, Dec 2, 2020 at 12:23 AM Jagannathan Raman <jag.raman@oracle.com> wrote:
From: Elena Ufimtseva <elena.ufimtseva@oracle.com>

Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Signed-off-by: John G Johnson <john.g.johnson@oracle.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 include/hw/remote/mpqemu-link.h |  4 ++++
 hw/remote/mpqemu-link.c         | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/include/hw/remote/mpqemu-link.h b/include/hw/remote/mpqemu-link.h
index 070ac77..cee9468 100644
--- a/include/hw/remote/mpqemu-link.h
+++ b/include/hw/remote/mpqemu-link.h
@@ -15,6 +15,8 @@
 #include "qemu/thread.h"
 #include "io/channel.h"
 #include "exec/hwaddr.h"
+#include "io/channel-socket.h"
+#include "hw/remote/proxy.h"

 #define REMOTE_MAX_FDS 8

@@ -65,6 +67,8 @@ typedef struct {
     int num_fds;
 } MPQemuMsg;

+uint64_t mpqemu_msg_send_and_await_reply(MPQemuMsg *msg, PCIProxyDev *pdev,
+                                         Error **errp);
 void mpqemu_msg_send(MPQemuMsg *msg, QIOChannel *ioc, Error **errp);
 void mpqemu_msg_recv(MPQemuMsg *msg, QIOChannel *ioc, Error **errp);

diff --git a/hw/remote/mpqemu-link.c b/hw/remote/mpqemu-link.c
index bbd9df3..18c8a54 100644
--- a/hw/remote/mpqemu-link.c
+++ b/hw/remote/mpqemu-link.c
@@ -17,6 +17,7 @@
 #include "qemu/iov.h"
 #include "qemu/error-report.h"
 #include "qemu/main-loop.h"
+#include "io/channel.h"

 /*
  * Send message over the ioc QIOChannel.
@@ -219,6 +220,43 @@ fail:
     }
 }

+/*
+ * Called from VCPU thread in non-coroutine context.

You could check that precondition in code early on, presumably.

The comment could use some further description, like "Send @msg and wait for a RET_MSG reply. Returns the associated u64 message code, or UINT64_MAX on error."

+ */
+uint64_t mpqemu_msg_send_and_await_reply(MPQemuMsg *msg, PCIProxyDev *pdev,
+                                         Error **errp)
+{
+    MPQemuMsg msg_reply = {0};
+    uint64_t ret = UINT64_MAX;
+    Error *local_err = NULL;
+

Should work with ERRP_GUARD instead

+    qemu_mutex_lock(&pdev->io_mutex);

Should work with QEMU_LOCK_GUARD

+    mpqemu_msg_send(msg, pdev->ioc, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        goto exit_send;
+    }
+

By making mpqemu_msg_send() return true on success, this should then become simply

if (!mpqemu_msg_send(msg, pdev->ioc, errp))
  return ret;

+    mpqemu_msg_recv(&msg_reply, pdev->ioc, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        goto exit_send;
+    }
+
+    if (!mpqemu_msg_valid(&msg_reply) || msg_reply.cmd != RET_MSG) {
+        error_setg(errp, "ERROR: Invalid reply received for command %d",
+                         msg->cmd);
+        goto exit_send;
+    } else {

that else is unneeded.

The function with automatic cleanups should be simpler.

+        ret = msg_reply.data.u64;
+    }
+
+ exit_send:
+    qemu_mutex_unlock(&pdev->io_mutex);
+
+    return ret;
+}
+
 bool mpqemu_msg_valid(MPQemuMsg *msg)
 {
     if (msg->cmd >= MPQEMU_CMD_MAX && msg->cmd < 0) {
--
1.8.3.1



--
Marc-André Lureau

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