[PATCH] pci: Enable bus-master on virtio_blk

From: Brandon Bergren

In qemu 9d7bd0826f2d19f88631ad7078662668148f7b5f, the behavior of vring
processing was changed to not run whenever bus-mastering is disabled.

Since we were never enabling it in the first place, OpenBIOS was no longer
able to access virtio disks on qemu.

Fix this by enabling bus-mastering before initializing.

Signed-off-by: Brandon Bergren 
---
 drivers/pci.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci.c b/drivers/pci.c
index 9d501d3..34ae69a 100644
--- a/drivers/pci.c
+++ b/drivers/pci.c
@@ -816,6 +816,9 @@ int virtio_blk_config_cb(const pci_config_t *config)
    	return 0;
    }

+	/* Enable bus mastering to ensure vring processing will run. */
+	ob_pci_enable_bus_master(config);
+
    ob_virtio_init(config->path, "virtio-blk", common_cfg, device_cfg,
    				notify_base, notify_mult, idx);
 #endif

[Mark Cave-Ayland]

On 13/05/2020 18:13, [e-mail] wrote:
> From: Brandon Bergren
>
> In qemu 9d7bd0826f2d19f88631ad7078662668148f7b5f, the behavior of vring
> processing was changed to not run whenever bus-mastering is disabled.
>
> Since we were never enabling it in the first place, OpenBIOS was no longer
> able to access virtio disks on qemu.
>
> Fix this by enabling bus-mastering before initializing.
> Signed-off-by: Brandon Bergren
>
> drivers/pci.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/pci.c b/drivers/pci.c
> index 9d501d3..34ae69a 100644
> --- a/drivers/pci.c
> +++ b/drivers/pci.c
> @@ -816,6 +816,9 @@ int virtio_blk_config_cb(const pci_config_t *config)
>    	return 0;
>    }
> /* Enable bus mastering to ensure vring processing will run. */
> ob_pci_enable_bus_master(config);
> ob_virtio_init(config->path, "virtio-blk", common_cfg, device_cfg,
>   			notify_base, notify_mult, idx);
>
> #endif

Hi Brandon,

Thanks a lot for this patch - I've been testing it this morning, and discovered that
whilst it fixed virtio for qemu-system-sparc64, I was still unable to boot from a
virtio device under qemu-system-ppc.

I've since discovered that this is because of another recent change in QEMU, so I'll
queue this patch and post a follow-up which fixes the qemu-system-ppc boot issue for me.

ATB,

Mark.