Re: [Qemu-devel] [PATCH v3 01/39] virtio-pci: get config on init

[Michael S. Tsirkin]

On Fri, Aug 05, 2011 at 08:52:25AM -0500, Anthony Liguori wrote:
> On 08/04/2011 08:05 AM, Avi Kivity wrote:
> >From: "Michael S. Tsirkin"<address@hidden>
> >
> >We originally did get config on map, so that
> >following write accesses are done on an updated config.
> >New memory API doesn't give us a callback
> >on map, and arguably, devices don't know when
> >cpu really can access there. So updating on
> >init seems cleaner.
> >
> >Signed-off-by: Michael S. Tsirkin<address@hidden>
> >Signed-off-by: Avi Kivity<address@hidden>
> >---
> >  hw/virtio-pci.c |    7 ++++---
> >  1 files changed, 4 insertions(+), 3 deletions(-)
> >
> >diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> >index d685243..ca1f12f 100644
> >--- a/hw/virtio-pci.c
> >+++ b/hw/virtio-pci.c
> >@@ -506,9 +506,6 @@ static void virtio_map(PCIDevice *pci_dev, int 
> >region_num,
> >      register_ioport_read(addr, config_len, 1, virtio_pci_config_readb, 
> > proxy);
> >      register_ioport_read(addr, config_len, 2, virtio_pci_config_readw, 
> > proxy);
> >      register_ioport_read(addr, config_len, 4, virtio_pci_config_readl, 
> > proxy);
> >-
> >-    if (vdev->config_len)
> >-        vdev->get_config(vdev, vdev->config);
> >  }
> >
> >  static void virtio_write_config(PCIDevice *pci_dev, uint32_t address,
> >@@ -689,6 +686,10 @@ void virtio_init_pci(VirtIOPCIProxy *proxy, 
> >VirtIODevice *vdev)
> >      proxy->host_features |= 0x1<<  VIRTIO_F_NOTIFY_ON_EMPTY;
> >      proxy->host_features |= 0x1<<  VIRTIO_F_BAD_FEATURE;
> >      proxy->host_features = vdev->get_features(vdev, proxy->host_features);
> >+
> >+    if (vdev->config_len) {
> >+        vdev->get_config(vdev, vdev->config);
> >+    }
> 
> Thinking more closely, I don't think this right.
> 
> Updating on map ensured that the config was refreshed after each
> time the bar was mapped.  In the very least, the config needs to be
> refreshed during reset because the guest may write to the guest
> space which should get cleared after reset.
> 
> Regards,
> 
> Anthony Liguori

Not sure I understand. Which register, for example,
do you have in mind?
Could you clarify please?


> >  }
> >
> >  static int virtio_blk_init_pci(PCIDevice *pci_dev)