[PULL 04/11] Revert "vfio: Avoid disabling and enabling vectors repeatedly in VFIO migration"

[Alex Williamson]

From: Longpeng(Mike) <longpeng2@huawei.com>

Commit ecebe53fe993 ("vfio: Avoid disabling and enabling vectors
repeatedly in VFIO migration") avoids inefficiently disabling and
enabling vectors repeatedly and lets the unmasked vectors be enabled
one by one.

But we want to batch multiple routes and defer the commit, and only
commit once outside the loop of setting vector notifiers, so we
cannot enable the vectors one by one in the loop now.

Revert that commit and we will take another way in the next patch,
it can not only avoid disabling/enabling vectors repeatedly, but
also satisfy our requirement of defer to commit.

Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
Link: https://lore.kernel.org/r/20220326060226.1892-5-longpeng2@huawei.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 hw/vfio/pci.c |   20 +++-----------------
 1 file changed, 3 insertions(+), 17 deletions(-)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 50562629ea8f..8bc36f081afd 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -572,9 +572,6 @@ static void vfio_msix_vector_release(PCIDevice *pdev, 
unsigned int nr)
 
 static void vfio_msix_enable(VFIOPCIDevice *vdev)
 {
-    PCIDevice *pdev = &vdev->pdev;
-    unsigned int nr, max_vec = 0;
-
     vfio_disable_interrupts(vdev);
 
     vdev->msi_vectors = g_new0(VFIOMSIVector, vdev->msix->entries);
@@ -593,22 +590,11 @@ static void vfio_msix_enable(VFIOPCIDevice *vdev)
      * triggering to userspace, then immediately release the vector, leaving
      * the physical device with no vectors enabled, but MSI-X enabled, just
      * like the guest view.
-     * If there are already unmasked vectors (in migration resume phase and
-     * some guest startups) which will be enabled soon, we can allocate all
-     * of them here to avoid inefficiently disabling and enabling vectors
-     * repeatedly later.
      */
-    if (!pdev->msix_function_masked) {
-        for (nr = 0; nr < msix_nr_vectors_allocated(pdev); nr++) {
-            if (!msix_is_masked(pdev, nr)) {
-                max_vec = nr;
-            }
-        }
-    }
-    vfio_msix_vector_do_use(pdev, max_vec, NULL, NULL);
-    vfio_msix_vector_release(pdev, max_vec);
+    vfio_msix_vector_do_use(&vdev->pdev, 0, NULL, NULL);
+    vfio_msix_vector_release(&vdev->pdev, 0);
 
-    if (msix_set_vector_notifiers(pdev, vfio_msix_vector_use,
+    if (msix_set_vector_notifiers(&vdev->pdev, vfio_msix_vector_use,
                                   vfio_msix_vector_release, NULL)) {
         error_report("vfio: msix_set_vector_notifiers failed");
     }