Re: [Spice-devel] [PATCH] drm/qxl: get vga ioports

From: Frediano Ziglio
Date: Mon Aug 05 2019 - 05:18:18 EST


>
> qxl has two modes: "native" (used by the drm driver) and "vga" (vga
> compatibility mode, typically used for boot display and firmware
> framebuffers).
>
> Accessing any vga ioport will switch the qxl device into vga mode.
> The qxl driver never does that, but other drivers accessing vga ports
> can trigger that too and therefore disturb qxl operation. So aquire
> the legacy vga ioports from vgaarb to avoid that.
>
> Reporducer: Boot kvm guest with both qxl and i915 vgpu, with qxl being

typo: "Reporducer"

> first in pci scan order.
>
> Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
> ---
> drivers/gpu/drm/qxl/qxl_drv.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/qxl/qxl_drv.c b/drivers/gpu/drm/qxl/qxl_drv.c
> index b57a37543613..8a2e86adc423 100644
> --- a/drivers/gpu/drm/qxl/qxl_drv.c
> +++ b/drivers/gpu/drm/qxl/qxl_drv.c
> @@ -87,9 +87,15 @@ qxl_pci_probe(struct pci_dev *pdev, const struct
> pci_device_id *ent)
> if (ret)
> goto disable_pci;
>
> + ret = vga_get_interruptible(pdev, VGA_RSRC_LEGACY_IO);
> + if (ret) {
> + DRM_ERROR("can't get legacy vga ports\n");
> + goto put_vga;

I suppose that if this fails it's secondary so should continue.
What happen configuring 2 QXL devices?
Only a card should provide VGA registers in the system so
if any other card provide them QXL won't work.

> + }
> +
> ret = qxl_device_init(qdev, &qxl_driver, pdev);
> if (ret)
> - goto disable_pci;
> + goto put_vga;
>
> ret = qxl_modeset_init(qdev);
> if (ret)
> @@ -109,6 +115,8 @@ qxl_pci_probe(struct pci_dev *pdev, const struct
> pci_device_id *ent)
> qxl_modeset_fini(qdev);
> unload:
> qxl_device_fini(qdev);
> +put_vga:
> + vga_put(pdev, VGA_RSRC_LEGACY_IO);

What happen if you didn't get the I/O? Maybe it's safe to
just call vga_put and avoid adding an additional label here?

> disable_pci:
> pci_disable_device(pdev);
> free_dev:
> @@ -126,6 +134,7 @@ qxl_pci_remove(struct pci_dev *pdev)
>
> qxl_modeset_fini(qdev);
> qxl_device_fini(qdev);
> + vga_put(pdev, VGA_RSRC_LEGACY_IO);
>
> dev->dev_private = NULL;
> kfree(qdev);

Frediano