[PATCH v2 42/58] i386/tdx: register the fd read callback with the main loop to read the quote data

[Xiaoyao Li]

From: Chenyi Qiang <chenyi.qiang@intel.com>

When TD guest invokes getquote tdvmcall, QEMU will register a async qio
task with default context when the qio channel is connected. However, as
there is a blocking action (recvmsg()) in qio_channel_read() and it will
block main thread and make TD guest have no response until the server
returns.

Set the io channel non-blocking and register the socket fd with the main
loop. Move the read operation into the callback. When the fd is readable,
inovke the callback to handle the quote data.

Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
 target/i386/kvm/tdx.c | 147 +++++++++++++++++++++++++++---------------
 1 file changed, 96 insertions(+), 51 deletions(-)

diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index 73d6cd88af9e..3cb2163a0335 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -997,6 +997,8 @@ struct tdx_get_quote_task {
     uint32_t apic_id;
     hwaddr gpa;
     uint64_t buf_len;
+    char *out_data;
+    uint64_t out_len;
     struct tdx_get_quote_header hdr;
     int event_notify_interrupt;
     QIOChannelSocket *ioc;
@@ -1082,78 +1084,53 @@ static void tdx_td_notify(struct tdx_get_quote_task *t)
     }
 }
 
-/*
- * TODO: If QGS doesn't reply for long time, make it an error and interrupt
- * guest.
- */
-static void tdx_handle_get_quote_connected(QIOTask *task, gpointer opaque)
+static void tdx_get_quote_read(void *opaque)
 {
     struct tdx_get_quote_task *t = opaque;
+    ssize_t size = 0;
     Error *err = NULL;
-    char *in_data = NULL;
-    char *out_data = NULL;
-    size_t out_len;
-    ssize_t size;
     MachineState *ms;
     TdxGuest *tdx;
 
-    t->hdr.error_code = cpu_to_le64(TDX_VP_GET_QUOTE_ERROR);
-    if (qio_task_propagate_error(task, NULL)) {
-        t->hdr.error_code = cpu_to_le64(TDX_VP_GET_QUOTE_QGS_UNAVAILABLE);
-        goto error;
-    }
-
-    in_data = g_malloc(le32_to_cpu(t->hdr.in_len));
-    if (address_space_read(&address_space_memory, t->gpa + sizeof(t->hdr),
-                           MEMTXATTRS_UNSPECIFIED, in_data,
-                           le32_to_cpu(t->hdr.in_len)) != MEMTX_OK) {
-        goto error;
-    }
-
-    if (qio_channel_write_all(QIO_CHANNEL(t->ioc), in_data,
-                              le32_to_cpu(t->hdr.in_len), &err) ||
-        err) {
-        t->hdr.error_code = cpu_to_le64(TDX_VP_GET_QUOTE_QGS_UNAVAILABLE);
-        goto error;
-    }
-
-    out_data = g_malloc(t->buf_len);
-    out_len = 0;
-    size = 0;
     while (true) {
         char *buf;
         size_t buf_size;
 
-        if (out_len < t->buf_len) {
-            buf = out_data + out_len;
-            buf_size = t->buf_len - out_len;
+        if (t->out_len < t->buf_len) {
+            buf = t->out_data + t->out_len;
+            buf_size = t->buf_len - t->out_len;
         } else {
             /*
              * The received data is too large to fit in the shared GPA.
              * Discard the received data and try to know the data size.
              */
-            buf = out_data;
+            buf = t->out_data;
             buf_size = t->buf_len;
         }
 
         size = qio_channel_read(QIO_CHANNEL(t->ioc), buf, buf_size, &err);
-        if (err) {
+        if (!size) {
             break;
         }
-        if (size <= 0) {
-            break;
+
+        if (size < 0) {
+            if (size == QIO_CHANNEL_ERR_BLOCK) {
+                return;
+            } else {
+                break;
+            }
         }
-        out_len += size;
+        t->out_len += size;
     }
     /*
-     * Treat partial read as success and let the QGS client to handle it 
because
-     * the client knows better about the QGS.
+     * If partial read successfully but return error at last, also treat it
+     * as failure.
      */
-    if (out_len == 0 && (err || size < 0)) {
+    if (size < 0) {
         t->hdr.error_code = cpu_to_le64(TDX_VP_GET_QUOTE_QGS_UNAVAILABLE);
         goto error;
     }
-    if (out_len > 0 && out_len > t->buf_len) {
+    if (t->out_len > 0 && t->out_len > t->buf_len) {
         /*
          * There is no specific error code defined for this case(E2BIG) at the
          * moment.
@@ -1161,20 +1138,20 @@ static void tdx_handle_get_quote_connected(QIOTask 
*task, gpointer opaque)
          * update the error code.
          */
         t->hdr.error_code = cpu_to_le64(TDX_VP_GET_QUOTE_ERROR);
-        t->hdr.out_len = cpu_to_le32(out_len);
+        t->hdr.out_len = cpu_to_le32(t->out_len);
         goto error_hdr;
     }
 
     if (address_space_write(
             &address_space_memory, t->gpa + sizeof(t->hdr),
-            MEMTXATTRS_UNSPECIFIED, out_data, out_len) != MEMTX_OK) {
+            MEMTXATTRS_UNSPECIFIED, t->out_data, t->out_len) != MEMTX_OK) {
         goto error;
     }
     /*
      * Even if out_len == 0, it's a success.  It's up to the QGS-client 
contract
      * how to interpret the zero-sized message as return message.
      */
-    t->hdr.out_len = cpu_to_le32(out_len);
+    t->hdr.out_len = cpu_to_le32(t->out_len);
     t->hdr.error_code = cpu_to_le64(TDX_VP_GET_QUOTE_SUCCESS);
 
 error:
@@ -1185,14 +1162,15 @@ error_hdr:
     if (address_space_write(
             &address_space_memory, t->gpa,
             MEMTXATTRS_UNSPECIFIED, &t->hdr, sizeof(t->hdr)) != MEMTX_OK) {
-        error_report("TDX: failed to updsate GetQuote header.\n");
+        error_report("TDX: failed to update GetQuote header.");
     }
     tdx_td_notify(t);
 
+    qemu_set_fd_handler(t->ioc->fd, NULL, NULL, NULL);
     qio_channel_close(QIO_CHANNEL(t->ioc), &err);
     object_unref(OBJECT(t->ioc));
-    g_free(in_data);
-    g_free(out_data);
+    g_free(t->out_data);
+    g_free(t);
 
     /* Maintain the number of in-flight requests. */
     ms = MACHINE(qdev_get_machine());
@@ -1200,7 +1178,71 @@ error_hdr:
     qemu_mutex_lock(&tdx->lock);
     tdx->quote_generation_num--;
     qemu_mutex_unlock(&tdx->lock);
+}
+
+/*
+ * TODO: If QGS doesn't reply for long time, make it an error and interrupt
+ * guest.
+ */
+static void tdx_handle_get_quote_connected(QIOTask *task, gpointer opaque)
+{
+    struct tdx_get_quote_task *t = opaque;
+    Error *err = NULL;
+    char *in_data = NULL;
+    MachineState *ms;
+    TdxGuest *tdx;
+
+    t->hdr.error_code = cpu_to_le64(TDX_VP_GET_QUOTE_ERROR);
+    if (qio_task_propagate_error(task, NULL)) {
+        t->hdr.error_code = cpu_to_le64(TDX_VP_GET_QUOTE_QGS_UNAVAILABLE);
+        goto error;
+    }
+
+    in_data = g_malloc(le32_to_cpu(t->hdr.in_len));
+    if (!in_data) {
+        goto error;
+    }
+
+    if (address_space_read(&address_space_memory, t->gpa + sizeof(t->hdr),
+                           MEMTXATTRS_UNSPECIFIED, in_data,
+                           le32_to_cpu(t->hdr.in_len)) != MEMTX_OK) {
+        goto error;
+    }
+
+    qio_channel_set_blocking(QIO_CHANNEL(t->ioc), false, NULL);
+
+    if (qio_channel_write_all(QIO_CHANNEL(t->ioc), in_data,
+                              le32_to_cpu(t->hdr.in_len), &err) ||
+        err) {
+        t->hdr.error_code = cpu_to_le64(TDX_VP_GET_QUOTE_QGS_UNAVAILABLE);
+        goto error;
+    }
+
+    g_free(in_data);
+    qemu_set_fd_handler(t->ioc->fd, tdx_get_quote_read, NULL, t);
+
+    return;
+error:
+    t->hdr.out_len = cpu_to_le32(0);
 
+    if (address_space_write(
+            &address_space_memory, t->gpa,
+            MEMTXATTRS_UNSPECIFIED, &t->hdr, sizeof(t->hdr)) != MEMTX_OK) {
+        error_report("TDX: failed to update GetQuote header.\n");
+    }
+    tdx_td_notify(t);
+
+    qio_channel_close(QIO_CHANNEL(t->ioc), &err);
+    object_unref(OBJECT(t->ioc));
+    g_free(t);
+    g_free(in_data);
+
+    /* Maintain the number of in-flight requests. */
+    ms = MACHINE(qdev_get_machine());
+    tdx = TDX_GUEST(ms->cgs);
+    qemu_mutex_lock(&tdx->lock);
+    tdx->quote_generation_num--;
+    qemu_mutex_unlock(&tdx->lock);
     return;
 }
 
@@ -1269,6 +1311,8 @@ static void tdx_handle_get_quote(X86CPU *cpu, struct 
kvm_tdx_vmcall *vmcall)
     t->apic_id = tdx->event_notify_apic_id;
     t->gpa = gpa;
     t->buf_len = buf_len;
+    t->out_data = g_malloc(t->buf_len);
+    t->out_len = 0;
     t->hdr = hdr;
     t->ioc = ioc;
 
@@ -1279,13 +1323,14 @@ static void tdx_handle_get_quote(X86CPU *cpu, struct 
kvm_tdx_vmcall *vmcall)
         qemu_mutex_unlock(&tdx->lock);
         vmcall->status_code = TDG_VP_VMCALL_RETRY;
         object_unref(OBJECT(ioc));
+        g_free(t->out_data);
         g_free(t);
         return;
     }
     tdx->quote_generation_num++;
     t->event_notify_interrupt = tdx->event_notify_interrupt;
     qio_channel_socket_connect_async(
-        ioc, tdx->quote_generation, tdx_handle_get_quote_connected, t, g_free,
+        ioc, tdx->quote_generation, tdx_handle_get_quote_connected, t, NULL,
         NULL);
     qemu_mutex_unlock(&tdx->lock);
 
-- 
2.34.1