From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51048) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XS8PR-0004wM-JR for qemu-devel@nongnu.org; Thu, 11 Sep 2014 13:43:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XS8PM-00067G-DJ for qemu-devel@nongnu.org; Thu, 11 Sep 2014 13:43:53 -0400 Date: Thu, 11 Sep 2014 20:47:01 +0300 From: "Michael S. Tsirkin" Message-ID: <20140911174701.GB27774@redhat.com> References: <20140911164533.24109.16197.stgit@bahia.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140911164533.24109.16197.stgit@bahia.local> Subject: Re: [Qemu-devel] [PATCH] virtio-pci: enable bus master for old guests List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Greg Kurz Cc: Cedric Le Goater , qemu-devel@nongnu.org, Anthony Liguori , qemu-stable@nongnu.org On Thu, Sep 11, 2014 at 06:45:33PM +0200, Greg Kurz wrote: > From: Michael S. Tsirkin > > commit cc943c36faa192cd4b32af8fe5edb31894017d35 > pci: Use bus master address space for delivering MSI/MSI-X messages > breaks virtio-net for rhel6.[56] x86 guests because they don't > enable bus mastering for virtio PCI devices. For the same reason, > rhel6.[56] ppc64 guests cannot boot on a virtio-blk disk anymore. > > Old guests forgot to enable bus mastering, enable it automatically on > DRIVER (ppc64 guests may never reach DRIVER_OK). We also need to prevent > these old guests to disable bus mastering (this happens when the driver > probes the device). And we must also re-enable bus mastering after migration. > > Cc: qemu-stable@nongnu.org > Reported-by: Greg Kurz > Signed-off-by: Michael S. Tsirkin > [ old guest detection on DRIVER, > squashed patch from Michael S. Tsirkin to re-enable bus mastering, > Greg Kurz ] > Tested-by: Cedric Le Goater > Signed-off-by: Greg Kurz I think this is too fragile. Let's try to figure out a strategy that does not depend on VIRTIO_PCI_FLAG_BUS_MASTER_BUG. > --- > hw/virtio/virtio-pci.c | 18 +++++++++++++----- > 1 file changed, 13 insertions(+), 5 deletions(-) > > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c > index ddb5da1..f981841 100644 > --- a/hw/virtio/virtio-pci.c > +++ b/hw/virtio/virtio-pci.c > @@ -317,9 +317,11 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val) > /* 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) && > + if ((val & VIRTIO_CONFIG_S_DRIVER) && > !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) { > proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG; > + memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region, > + true); > } > break; > case VIRTIO_MSI_CONFIG_VECTOR: > @@ -473,10 +475,14 @@ static void virtio_write_config(PCIDevice *pci_dev, uint32_t address, > pci_default_write_config(pci_dev, address, val, len); > > if (range_covers_byte(address, len, PCI_COMMAND) && > - !(pci_dev->config[PCI_COMMAND] & PCI_COMMAND_MASTER) && > - !(proxy->flags & VIRTIO_PCI_FLAG_BUS_MASTER_BUG)) { > - virtio_pci_stop_ioeventfd(proxy); > - virtio_set_status(vdev, vdev->status & ~VIRTIO_CONFIG_S_DRIVER_OK); > + !(pci_dev->config[PCI_COMMAND] & PCI_COMMAND_MASTER)) { > + if (proxy->flags & VIRTIO_PCI_FLAG_BUS_MASTER_BUG) { > + memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region, > + true); > + } else { > + virtio_pci_stop_ioeventfd(proxy); > + virtio_set_status(vdev, vdev->status & ~VIRTIO_CONFIG_S_DRIVER_OK); > + } > } > } > > @@ -890,6 +896,8 @@ static void virtio_pci_vmstate_change(DeviceState *d, bool running) > if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) && > !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) { > proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG; > + memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region, > + true); > } > virtio_pci_start_ioeventfd(proxy); > } else {