From bb249ed9187a4eb62c8ca9331b6e609c17d32dfb Mon Sep 17 00:00:00 2001
From: Alex Williamson <alex.williamson@redhat.com>
Date: Thu, 17 Jun 2010 18:12:53 -0300
Subject: [PATCH 3/4] Don't check for bus master for old guests
RH-Author: Alex Williamson <alex.williamson@redhat.com>
Message-id: <20100617181136.5443.9919.stgit@localhost.localdomain>
Patchwork-id: 9960
O-Subject: [RHEL6.0 qemu-kvm PATCH v2] Don't check for bus master for old guests
Bugzilla: 596014
RH-Acked-by: Amit Shah <amit.shah@redhat.com>
RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
RH-Acked-by: Juan Quintela <quintela@redhat.com>
From: Alexander Graf <agraf@suse.de>
Bugzilla: 596014
Upstream commit: c81131db15dd1844d0db1d51f3cd7a105cfd2cf3
Older Linux guests don't activate the bus master enable bit. So for those we
can just try to be clever and track if they set the DEVICE_OK bit even though
bus mastering is still disabled.
Under that condition we can disable the windows safety check. With that logic
in place both guests should work just fine. Without PCI hotplug breaks
virtio-net in Linux < 2.6.34 guests.
Signed-off-by: Alexander Graf <agraf@suse.de>
CC: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
---
v2: Fix bug noted by Amit (also submitted upstream)
Fix whitespace to match upstream in virtio_write_config()
hw/virtio-pci.c | 27 +++++++++++++++++++++++++--
1 files changed, 25 insertions(+), 2 deletions(-)
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
hw/virtio-pci.c | 27 +++++++++++++++++++++++++--
1 files changed, 25 insertions(+), 2 deletions(-)
diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index 4aeabbf..dba38b6 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -80,6 +80,10 @@
* 12 is historical, and due to x86 page size. */
#define VIRTIO_PCI_QUEUE_ADDR_SHIFT 12
+/* We can catch some guest bugs inside here so we continue supporting older
+ guests. */
+#define VIRTIO_PCI_BUG_BUS_MASTER (1 << 0)
+
/* QEMU doesn't strictly need write barriers since everything runs in
* lock-step. We'll leave the calls to wmb() in though to make it obvious for
* KVM or if kqemu gets SMP support.
@@ -91,6 +95,7 @@
typedef struct {
PCIDevice pci_dev;
VirtIODevice *vdev;
+ uint32_t bugs;
uint32_t addr;
uint32_t class_code;
uint32_t nvectors;
@@ -145,6 +150,13 @@ static int virtio_pci_load_config(void * opaque, QEMUFile *f)
if (proxy->vdev->config_vector != VIRTIO_NO_VECTOR) {
return msix_vector_use(&proxy->pci_dev, proxy->vdev->config_vector);
}
+
+ /* Try to find out if the guest has bus master disabled, but is
+ in ready state. Then we have a buggy guest OS. */
+ if ((proxy->vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
+ !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
+ proxy->bugs |= VIRTIO_PCI_BUG_BUS_MASTER;
+ }
return 0;
}
@@ -169,6 +181,7 @@ static void virtio_pci_reset(DeviceState *d)
VirtIOPCIProxy *proxy = container_of(d, VirtIOPCIProxy, pci_dev.qdev);
virtio_reset(proxy->vdev);
msix_reset(&proxy->pci_dev);
+ proxy->bugs = 0;
}
static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
@@ -212,6 +225,14 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
virtio_reset(proxy->vdev);
msix_unuse_all_vectors(&proxy->pci_dev);
}
+
+ /* Linux before 2.6.34 sets the device as OK without enabling
+ the PCI device bus master bit. In this case we need to disable
+ some safety checks. */
+ if ((val & VIRTIO_CONFIG_S_DRIVER_OK) &&
+ !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
+ proxy->bugs |= VIRTIO_PCI_BUG_BUS_MASTER;
+ }
break;
case VIRTIO_MSI_CONFIG_VECTOR:
msix_vector_unuse(&proxy->pci_dev, vdev->config_vector);
@@ -378,8 +399,10 @@ static void virtio_write_config(PCIDevice *pci_dev, uint32_t address,
if (PCI_COMMAND == address) {
if (!(val & PCI_COMMAND_MASTER)) {
- virtio_set_status(proxy->vdev,
- proxy->vdev->status & ~VIRTIO_CONFIG_S_DRIVER_OK);
+ if (!(proxy->bugs & VIRTIO_PCI_BUG_BUS_MASTER)) {
+ virtio_set_status(proxy->vdev,
+ proxy->vdev->status & ~VIRTIO_CONFIG_S_DRIVER_OK);
+ }
}
}
--
1.7.0.3