qemu-kvm/kvm-vfio-increase-the-cap-on-number-of-assigned-devices-.patch

From 2b89558946fc396c6ecb10249b69960d2a74e18f Mon Sep 17 00:00:00 2001
From: Bandan Das <bsd@redhat.com>
Date: Wed, 12 Jun 2019 16:56:23 +0100
Subject: [PATCH 3/3] vfio: increase the cap on number of assigned devices to
 64

RH-Author: Bandan Das <bsd@redhat.com>
Message-id: <jpgy32691zc.fsf@linux.bootlegged.copy>
Patchwork-id: 88653
O-Subject: [RHEL-AV-8.1.0 qemu-kvm PATCH] vfio: increase the cap on number of assigned devices to 64
Bugzilla: 1719823
RH-Acked-by: Alex Williamson <alex.williamson@redhat.com>
RH-Acked-by: Auger Eric <eric.auger@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1719823
Brew: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=22124174
Branch: rhel-av-8.1.0/master-4.0.0
Upstrea: N/A, the device limit change is downstream only

In addition to bumping up the limit, also add a property for
future-proofing. This needs to be set for every assigned device
or via "global": -global vfio-pci.x-assigned-device-limit

RHEL Notes:
For each vm using vfio, there is at least a container fd. For
each assigned device, there is likely a group fd, a device fd,
an error signaling fd and a device request fd. Assuming SR-IOV
VFs, vectors/device considering MSI/MSI-X could be ~3-5. Therefore,
we have ~14 file descriptors per device or 897 for 64 devices.
The default open fd limit is 1024 on Linux but libvirt bumps it to
8192 and the qemu process inherits that value as well.

Signed-off-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
 hw/vfio/pci.c | 20 +++++++++++++++++---
 hw/vfio/pci.h |  1 +
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 7c998af..7c0d93a 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -36,11 +36,13 @@
 #include "qapi/error.h"
 
 #define MSIX_CAP_LENGTH 12
-#define MAX_DEV_ASSIGN_CMDLINE 32
 
 #define TYPE_VFIO_PCI "vfio-pci"
 #define PCI_VFIO(obj)    OBJECT_CHECK(VFIOPCIDevice, obj, TYPE_VFIO_PCI)
 
+/* 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);
 
@@ -2810,15 +2812,24 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
     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 >= MAX_DEV_ASSIGN_CMDLINE) {
+    if (i >= vdev->assigned_device_limit) {
         error_setg(errp, "Maximum supported vfio devices (%d) "
-                     "already attached", MAX_DEV_ASSIGN_CMDLINE);
+                     "already attached", vdev->assigned_device_limit);
         return;
     }
 
@@ -3223,6 +3234,9 @@ 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 c11c3f1..29a8add 100644
--- a/hw/vfio/pci.h
+++ b/hw/vfio/pci.h
@@ -136,6 +136,7 @@ typedef 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;
-- 
1.8.3.1