qemu-kvm/SOURCES/kvm-vhost-Decouple-vhost_svq_add-from-VirtQueueElement.patch

From 5c8de23e185a1a1f0b19eac3c9fa03411c9f545c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Eugenio=20P=C3=A9rez?= <eperezma@redhat.com>
Date: Thu, 21 Jul 2022 15:38:55 +0200
Subject: [PATCH 14/32] vhost: Decouple vhost_svq_add from VirtQueueElement
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RH-Author: Eugenio Pérez <eperezma@redhat.com>
RH-MergeRequest: 108: Net Control Virtqueue shadow Support
RH-Commit: [14/27] 463087dd316adc91b9c7a4e6634c6fc1745c1849 (eperezmartin/qemu-kvm)
RH-Bugzilla: 1939363
RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>
RH-Acked-by: Cindy Lu <lulu@redhat.com>
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>

Bugzilla: https://bugzilla.redhat.com/1939363

Upstream Status: git://git.qemu.org/qemu.git

commit 1f46ae65d85f677b660bda46685dd3e94885a7cb
Author: Eugenio Pérez <eperezma@redhat.com>
Date:   Wed Jul 20 08:59:33 2022 +0200

    vhost: Decouple vhost_svq_add from VirtQueueElement

    VirtQueueElement comes from the guest, but we're heading SVQ to be able
    to modify the element presented to the device without the guest's
    knowledge.

    To do so, make SVQ accept sg buffers directly, instead of using
    VirtQueueElement.

    Add vhost_svq_add_element to maintain element convenience.

    Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
    Acked-by: Jason Wang <jasowang@redhat.com>
    Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
    Signed-off-by: Jason Wang <jasowang@redhat.com>

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-shadow-virtqueue.c | 33 ++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
index 1d2bab287b..3cec03d709 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -172,30 +172,31 @@ static bool vhost_svq_vring_write_descs(VhostShadowVirtqueue *svq, hwaddr *sg,
 }
 
 static bool vhost_svq_add_split(VhostShadowVirtqueue *svq,
-                                VirtQueueElement *elem, unsigned *head)
+                                const struct iovec *out_sg, size_t out_num,
+                                const struct iovec *in_sg, size_t in_num,
+                                unsigned *head)
 {
     unsigned avail_idx;
     vring_avail_t *avail = svq->vring.avail;
     bool ok;
-    g_autofree hwaddr *sgs = g_new(hwaddr, MAX(elem->out_num, elem->in_num));
+    g_autofree hwaddr *sgs = g_new(hwaddr, MAX(out_num, in_num));
 
     *head = svq->free_head;
 
     /* We need some descriptors here */
-    if (unlikely(!elem->out_num && !elem->in_num)) {
+    if (unlikely(!out_num && !in_num)) {
         qemu_log_mask(LOG_GUEST_ERROR,
                       "Guest provided element with no descriptors");
         return false;
     }
 
-    ok = vhost_svq_vring_write_descs(svq, sgs, elem->out_sg, elem->out_num,
-                                     elem->in_num > 0, false);
+    ok = vhost_svq_vring_write_descs(svq, sgs, out_sg, out_num, in_num > 0,
+                                     false);
     if (unlikely(!ok)) {
         return false;
     }
 
-    ok = vhost_svq_vring_write_descs(svq, sgs, elem->in_sg, elem->in_num, false,
-                                     true);
+    ok = vhost_svq_vring_write_descs(svq, sgs, in_sg, in_num, false, true);
     if (unlikely(!ok)) {
         return false;
     }
@@ -237,17 +238,19 @@ static void vhost_svq_kick(VhostShadowVirtqueue *svq)
  *
  * Return -EINVAL if element is invalid, -ENOSPC if dev queue is full
  */
-static int vhost_svq_add(VhostShadowVirtqueue *svq, VirtQueueElement *elem)
+static int vhost_svq_add(VhostShadowVirtqueue *svq, const struct iovec *out_sg,
+                          size_t out_num, const struct iovec *in_sg,
+                          size_t in_num, VirtQueueElement *elem)
 {
     unsigned qemu_head;
-    unsigned ndescs = elem->in_num + elem->out_num;
+    unsigned ndescs = in_num + out_num;
     bool ok;
 
     if (unlikely(ndescs > vhost_svq_available_slots(svq))) {
         return -ENOSPC;
     }
 
-    ok = vhost_svq_add_split(svq, elem, &qemu_head);
+    ok = vhost_svq_add_split(svq, out_sg, out_num, in_sg, in_num, &qemu_head);
     if (unlikely(!ok)) {
         g_free(elem);
         return -EINVAL;
@@ -258,6 +261,14 @@ static int vhost_svq_add(VhostShadowVirtqueue *svq, VirtQueueElement *elem)
     return 0;
 }
 
+/* Convenience wrapper to add a guest's element to SVQ */
+static int vhost_svq_add_element(VhostShadowVirtqueue *svq,
+                                 VirtQueueElement *elem)
+{
+    return vhost_svq_add(svq, elem->out_sg, elem->out_num, elem->in_sg,
+                         elem->in_num, elem);
+}
+
 /**
  * Forward available buffers.
  *
@@ -294,7 +305,7 @@ static void vhost_handle_guest_kick(VhostShadowVirtqueue *svq)
                 break;
             }
 
-            r = vhost_svq_add(svq, elem);
+            r = vhost_svq_add_element(svq, elem);
             if (unlikely(r != 0)) {
                 if (r == -ENOSPC) {
                     /*
-- 
2.31.1