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From 9d8b817bfe327873c009fa4621c0308e7f3bc5de Mon Sep 17 00:00:00 2001
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From: "Michael S. Tsirkin" <mst@redhat.com>
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Date: Mon, 29 Sep 2014 11:27:32 +0300
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Subject: [PATCH] Revert "virtio-pci: fix migration for pci bus master"
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This reverts commit 4d43d3f3c8147ade184df9a1e9e82826edd39e19.
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Reported to break PPC guests.
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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(cherry picked from commit 45363e46aeebfc99753389649eac7c7fc22bfe52)
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---
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hw/virtio/virtio-pci.c | 39 +++++++++++++++++++--------------------
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1 file changed, 19 insertions(+), 20 deletions(-)
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diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
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index c19c4d6..58ebbcf 100644
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--- a/hw/virtio/virtio-pci.c
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+++ b/hw/virtio/virtio-pci.c
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@@ -86,6 +86,9 @@
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* 12 is historical, and due to x86 page size. */
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#define VIRTIO_PCI_QUEUE_ADDR_SHIFT 12
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+/* Flags track per-device state like workarounds for quirks in older guests. */
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+#define VIRTIO_PCI_FLAG_BUS_MASTER_BUG (1 << 0)
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+
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static void virtio_pci_bus_new(VirtioBusState *bus, size_t bus_size,
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VirtIOPCIProxy *dev);
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@@ -320,6 +323,14 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
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proxy->pci_dev.config[PCI_COMMAND] |
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PCI_COMMAND_MASTER, 1);
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}
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+
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+ /* Linux before 2.6.34 sets the device as OK without enabling
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+ the PCI device bus master bit. In this case we need to disable
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+ some safety checks. */
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+ if ((val & VIRTIO_CONFIG_S_DRIVER_OK) &&
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+ !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
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+ proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
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+ }
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break;
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case VIRTIO_MSI_CONFIG_VECTOR:
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msix_vector_unuse(&proxy->pci_dev, vdev->config_vector);
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@@ -469,18 +480,13 @@ static void virtio_write_config(PCIDevice *pci_dev, uint32_t address,
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VirtIOPCIProxy *proxy = DO_UPCAST(VirtIOPCIProxy, pci_dev, pci_dev);
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VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
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- uint8_t cmd = proxy->pci_dev.config[PCI_COMMAND];
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-
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pci_default_write_config(pci_dev, address, val, len);
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if (range_covers_byte(address, len, PCI_COMMAND) &&
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!(pci_dev->config[PCI_COMMAND] & PCI_COMMAND_MASTER) &&
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- (cmd & PCI_COMMAND_MASTER)) {
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- /* Bus driver disables bus mastering - make it act
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- * as a kind of reset to render the device quiescent. */
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+ !(proxy->flags & VIRTIO_PCI_FLAG_BUS_MASTER_BUG)) {
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virtio_pci_stop_ioeventfd(proxy);
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- virtio_reset(vdev);
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- msix_unuse_all_vectors(&proxy->pci_dev);
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+ virtio_set_status(vdev, vdev->status & ~VIRTIO_CONFIG_S_DRIVER_OK);
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}
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}
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@@ -889,19 +895,11 @@ static void virtio_pci_vmstate_change(DeviceState *d, bool running)
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VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
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if (running) {
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- /* Linux before 2.6.34 drives the device without enabling
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- the PCI device bus master bit. Enable it automatically
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- for the guest. This is a PCI spec violation but so is
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- initiating DMA with bus master bit clear.
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- Note: this only makes a difference when migrating
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- across QEMU versions from an old QEMU, as for new QEMU
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- bus master and driver bits are always in sync.
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- TODO: consider enabling conditionally for compat machine types. */
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- if (vdev->status & (VIRTIO_CONFIG_S_ACKNOWLEDGE |
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- VIRTIO_CONFIG_S_DRIVER)) {
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- pci_default_write_config(&proxy->pci_dev, PCI_COMMAND,
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- proxy->pci_dev.config[PCI_COMMAND] |
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- PCI_COMMAND_MASTER, 1);
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+ /* Try to find out if the guest has bus master disabled, but is
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+ in ready state. Then we have a buggy guest OS. */
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+ if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
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+ !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
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+ proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
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}
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virtio_pci_start_ioeventfd(proxy);
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} else {
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@@ -1045,6 +1043,7 @@ static void virtio_pci_reset(DeviceState *qdev)
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virtio_pci_stop_ioeventfd(proxy);
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virtio_bus_reset(bus);
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msix_unuse_all_vectors(&proxy->pci_dev);
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+ proxy->flags &= ~VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
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}
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static Property virtio_pci_properties[] = {
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