From 55dcef9d806aa530f10e3ca42eb24d52f850d674 Mon Sep 17 00:00:00 2001
From: Bandan Das <bsd@redhat.com>
Date: Tue, 3 Dec 2013 20:05:13 +0100
Subject: vfio: cap number of devices that can be assigned

RH-Author: Bandan Das <bsd@redhat.com>
Message-id: <1386101113-31560-3-git-send-email-bsd@redhat.com>
Patchwork-id: 55984
O-Subject: [PATCH RHEL7 qemu-kvm v2 2/2] vfio: cap number of devices that can be assigned
Bugzilla: 678368
RH-Acked-by: Alex Williamson <alex.williamson@redhat.com>
RH-Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>

Go through all groups to get count of total number of devices
active to enforce limit

Reasoning from Alex for the limit(32) - Assuming 3 slots per
device, with 125 slots (number of memory slots for RHEL 7),
we can support almost 40 devices and still have few slots left
for other uses. Stepping down a bit, the number 32 arbitrarily
matches the number of slots on a PCI bus and is also a nice power
of two.

Count of slots increased to 509 later so we could increase limit
to 64 as some usecases require more than 32 devices.

Signed-off-by: Bandan Das <bsd@redhat.com>
---
 hw/vfio/pci.c | 29 ++++++++++++++++++++++++++++-
 hw/vfio/pci.h |  1 +
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 7b45353ce2..eb725a3aee 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -45,6 +45,9 @@
 
 #define TYPE_VFIO_PCI_NOHOTPLUG "vfio-pci-nohotplug"
 
+/* RHEL only: Set once for the first assigned dev */
+static uint16_t device_limit;
+
 static void vfio_disable_interrupts(VFIOPCIDevice *vdev);
 static void vfio_mmap_set_enabled(VFIOPCIDevice *vdev, bool enabled);
 
@@ -2807,9 +2810,30 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
     ssize_t len;
     struct stat st;
     int groupid;
-    int i, ret;
+    int ret, i = 0;
     bool is_mdev;
 
+    if (device_limit && device_limit != vdev->assigned_device_limit) {
+            error_setg(errp, "Assigned device limit has been redefined. "
+                       "Old:%d, New:%d",
+                       device_limit, vdev->assigned_device_limit);
+            return;
+    } else {
+        device_limit = vdev->assigned_device_limit;
+    }
+
+    QLIST_FOREACH(group, &vfio_group_list, next) {
+        QLIST_FOREACH(vbasedev_iter, &group->device_list, next) {
+            i++;
+        }
+    }
+
+    if (i >= vdev->assigned_device_limit) {
+        error_setg(errp, "Maximum supported vfio devices (%d) "
+                     "already attached", vdev->assigned_device_limit);
+        return;
+    }
+
     if (!vdev->vbasedev.sysfsdev) {
         if (!(~vdev->host.domain || ~vdev->host.bus ||
               ~vdev->host.slot || ~vdev->host.function)) {
@@ -3246,6 +3270,9 @@ static Property vfio_pci_dev_properties[] = {
     DEFINE_PROP_BOOL("x-no-kvm-msix", VFIOPCIDevice, no_kvm_msix, false),
     DEFINE_PROP_BOOL("x-no-geforce-quirks", VFIOPCIDevice,
                      no_geforce_quirks, false),
+    /* RHEL only */
+    DEFINE_PROP_UINT16("x-assigned-device-limit", VFIOPCIDevice,
+                       assigned_device_limit, 64),
     DEFINE_PROP_BOOL("x-no-kvm-ioeventfd", VFIOPCIDevice, no_kvm_ioeventfd,
                      false),
     DEFINE_PROP_BOOL("x-no-vfio-ioeventfd", VFIOPCIDevice, no_vfio_ioeventfd,
diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
index 64777516d1..e0fe6ca97e 100644
--- a/hw/vfio/pci.h
+++ b/hw/vfio/pci.h
@@ -139,6 +139,7 @@ struct VFIOPCIDevice {
     EventNotifier err_notifier;
     EventNotifier req_notifier;
     int (*resetfn)(struct VFIOPCIDevice *);
+    uint16_t assigned_device_limit;
     uint32_t vendor_id;
     uint32_t device_id;
     uint32_t sub_vendor_id;
-- 
2.27.0