Re: [PATCH v1] virtio-pci: Fix legacy device flag setting error in probe

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On 2023-07-20 p.m.1:14, Michael S. Tsirkin wrote:
External email: Use caution opening links or attachments


On Thu, Jul 20, 2023 at 10:27:04AM +0800, Jason Wang wrote:
On Wed, Jul 19, 2023 at 11:46 PM Feng Liu <feliu@xxxxxxxxxx> wrote:

The 'is_legacy' flag is used to differentiate between legacy vs modern
device. Currently, it is based on the value of vp_dev->ldev.ioaddr.
However, due to the shared memory of the union between struct
virtio_pci_legacy_device and struct virtio_pci_modern_device, when
virtio_pci_modern_probe modifies the content of struct
virtio_pci_modern_device, it affects the content of struct
virtio_pci_legacy_device, and ldev.ioaddr is no longer zero, causing
the 'is_legacy' flag to be set as true. To resolve issue, when legacy
device is probed, mark 'is_legacy' as true, when modern device is
probed, keep 'is_legacy' as false.

Fixes: 4f0fc22534e3 ("virtio_pci: Optimize virtio_pci_device structure size")
Signed-off-by: Feng Liu <feliu@xxxxxxxxxx>
Reviewed-by: Parav Pandit <parav@xxxxxxxxxx>
Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx>
---
  drivers/virtio/virtio_pci_common.c | 2 --
  drivers/virtio/virtio_pci_legacy.c | 1 +
  2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index a6c86f916dbd..c2524a7207cf 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -557,8 +557,6 @@ static int virtio_pci_probe(struct pci_dev *pci_dev,

         pci_set_master(pci_dev);

-       vp_dev->is_legacy = vp_dev->ldev.ioaddr ? true : false;
-
         rc = register_virtio_device(&vp_dev->vdev);
         reg_dev = vp_dev;
         if (rc)
diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
index 2257f1b3d8ae..d9cbb02b35a1 100644
--- a/drivers/virtio/virtio_pci_legacy.c
+++ b/drivers/virtio/virtio_pci_legacy.c
@@ -223,6 +223,7 @@ int virtio_pci_legacy_probe(struct virtio_pci_device *vp_dev)
         vp_dev->config_vector = vp_config_vector;
         vp_dev->setup_vq = setup_vq;
         vp_dev->del_vq = del_vq;
+       vp_dev->is_legacy = true;

This seems break force_legacy for modern device:

         if (force_legacy) {
                 rc = virtio_pci_legacy_probe(vp_dev);
                 /* Also try modern mode if we can't map BAR0 (no IO space). */
                 if (rc == -ENODEV || rc == -ENOMEM)
                         rc = virtio_pci_modern_probe(vp_dev);

Thanks

don't see the breakage here - can you explain a bit more?

Hi, Jason

I also think there is no breakage herea and gave an explanation in another email, please have a see.

So are there any comments about this bug fix patch? Can this patch pass the review?

Thanks
Feng


         return 0;
  }
--
2.37.1 (Apple Git-137.1)


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