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Blame SOURCES/0013-vfio-cap-number-of-devices-that-can-be-assigned.patch

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From 55dcef9d806aa530f10e3ca42eb24d52f850d674 Mon Sep 17 00:00:00 2001
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From: Bandan Das <bsd@redhat.com>
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Date: Tue, 3 Dec 2013 20:05:13 +0100
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Subject: vfio: cap number of devices that can be assigned
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RH-Author: Bandan Das <bsd@redhat.com>
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Message-id: <1386101113-31560-3-git-send-email-bsd@redhat.com>
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Patchwork-id: 55984
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O-Subject: [PATCH RHEL7 qemu-kvm v2 2/2] vfio: cap number of devices that can be assigned
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Bugzilla: 678368
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RH-Acked-by: Alex Williamson <alex.williamson@redhat.com>
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RH-Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
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RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
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Go through all groups to get count of total number of devices
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active to enforce limit
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Reasoning from Alex for the limit(32) - Assuming 3 slots per
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device, with 125 slots (number of memory slots for RHEL 7),
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we can support almost 40 devices and still have few slots left
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for other uses. Stepping down a bit, the number 32 arbitrarily
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matches the number of slots on a PCI bus and is also a nice power
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of two.
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Count of slots increased to 509 later so we could increase limit
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to 64 as some usecases require more than 32 devices.
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Signed-off-by: Bandan Das <bsd@redhat.com>
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---
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 hw/vfio/pci.c | 29 ++++++++++++++++++++++++++++-
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 hw/vfio/pci.h |  1 +
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 2 files changed, 29 insertions(+), 1 deletion(-)
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diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
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index 7b45353ce2..eb725a3aee 100644
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--- a/hw/vfio/pci.c
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+++ b/hw/vfio/pci.c
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@@ -45,6 +45,9 @@
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 #define TYPE_VFIO_PCI_NOHOTPLUG "vfio-pci-nohotplug"
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+/* RHEL only: Set once for the first assigned dev */
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+static uint16_t device_limit;
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+
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 static void vfio_disable_interrupts(VFIOPCIDevice *vdev);
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 static void vfio_mmap_set_enabled(VFIOPCIDevice *vdev, bool enabled);
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@@ -2807,9 +2810,30 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
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     ssize_t len;
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     struct stat st;
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     int groupid;
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-    int i, ret;
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+    int ret, i = 0;
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     bool is_mdev;
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+    if (device_limit && device_limit != vdev->assigned_device_limit) {
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+            error_setg(errp, "Assigned device limit has been redefined. "
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+                       "Old:%d, New:%d",
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+                       device_limit, vdev->assigned_device_limit);
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+            return;
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+    } else {
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+        device_limit = vdev->assigned_device_limit;
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+    }
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+
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+    QLIST_FOREACH(group, &vfio_group_list, next) {
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+        QLIST_FOREACH(vbasedev_iter, &group->device_list, next) {
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+            i++;
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+        }
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+    }
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+
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+    if (i >= vdev->assigned_device_limit) {
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+        error_setg(errp, "Maximum supported vfio devices (%d) "
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+                     "already attached", vdev->assigned_device_limit);
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+        return;
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+    }
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+
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     if (!vdev->vbasedev.sysfsdev) {
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         if (!(~vdev->host.domain || ~vdev->host.bus ||
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               ~vdev->host.slot || ~vdev->host.function)) {
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@@ -3246,6 +3270,9 @@ static Property vfio_pci_dev_properties[] = {
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     DEFINE_PROP_BOOL("x-no-kvm-msix", VFIOPCIDevice, no_kvm_msix, false),
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     DEFINE_PROP_BOOL("x-no-geforce-quirks", VFIOPCIDevice,
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                      no_geforce_quirks, false),
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+    /* RHEL only */
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+    DEFINE_PROP_UINT16("x-assigned-device-limit", VFIOPCIDevice,
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+                       assigned_device_limit, 64),
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     DEFINE_PROP_BOOL("x-no-kvm-ioeventfd", VFIOPCIDevice, no_kvm_ioeventfd,
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                      false),
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     DEFINE_PROP_BOOL("x-no-vfio-ioeventfd", VFIOPCIDevice, no_vfio_ioeventfd,
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diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
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index 64777516d1..e0fe6ca97e 100644
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--- a/hw/vfio/pci.h
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+++ b/hw/vfio/pci.h
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@@ -139,6 +139,7 @@ struct VFIOPCIDevice {
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     EventNotifier err_notifier;
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     EventNotifier req_notifier;
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     int (*resetfn)(struct VFIOPCIDevice *);
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+    uint16_t assigned_device_limit;
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     uint32_t vendor_id;
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     uint32_t device_id;
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     uint32_t sub_vendor_id;
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-- 
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2.27.0
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