[PATCH 2/3] drm/vmwgfx: Print errors when running on broken/unsupported configs

[Maaz Mombasawala (VMware]

On 3/20/23 19:09, Zack Rusin wrote:
> From: Zack Rusin <zackr at vmware.com>
> 
> virtualbox implemented an incomplete version of the svga device which
> they decided to drop soon after the initial release. The device was
> always broken in various ways and never supported by vmwgfx.
> 
> vmwgfx should refuse to load on those configurations but currently
> drm has no way of reloading fbdev when the specific pci driver refuses
> to load, which would leave users without a usable fb. Instead of
> refusing to load print an error and disable a bunch of functionality
> that virtualbox never implemented to at least get fb to work on their
> setup.
> 
> Signed-off-by: Zack Rusin <zackr at vmware.com>
> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 29 +++++++++++++++++++++++++++++
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.h |  2 ++
>  drivers/gpu/drm/vmwgfx/vmwgfx_msg.c |  9 +++++++++
>  3 files changed, 40 insertions(+)
> 
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> index 2588615a2a38..8b24ecf60e3e 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> @@ -45,6 +45,9 @@
>  #include <drm/ttm/ttm_placement.h>
>  #include <generated/utsrelease.h>
>  
> +#ifdef CONFIG_X86
> +#include <asm/hypervisor.h>
> +#endif
>  #include <linux/cc_platform.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/module.h>
> @@ -897,6 +900,16 @@ static int vmw_driver_load(struct vmw_private *dev_priv, u32 pci_id)
>  				 cap2_names, ARRAY_SIZE(cap2_names));
>  	}
>  
> +	if (!vmwgfx_supported(dev_priv)) {
> +		vmw_disable_backdoor();
> +		drm_err_once(&dev_priv->drm,
> +			     "vmwgfx seems to be running on an unsupported hypervisor.");
> +		drm_err_once(&dev_priv->drm,
> +			     "This configuration is likely broken.");
> +		drm_err_once(&dev_priv->drm,
> +			     "Please switch to a supported graphics device to avoid problems.");
> +	}
> +
>  	ret = vmw_dma_select_mode(dev_priv);
>  	if (unlikely(ret != 0)) {
>  		drm_info(&dev_priv->drm,
> @@ -1320,6 +1333,22 @@ static void vmw_master_drop(struct drm_device *dev,
>  	vmw_kms_legacy_hotspot_clear(dev_priv);
>  }
>  
> +bool vmwgfx_supported(struct vmw_private *vmw)
> +{
> +#if defined(CONFIG_X86)
> +	return hypervisor_is_type(X86_HYPER_VMWARE);
> +#elif defined(CONFIG_ARM64)
> +	/*
> +	 * On aarch64 only svga3 is supported
> +	 */
> +	return vmw->pci_id == VMWGFX_PCI_ID_SVGA3;
> +#else
> +	drm_warn_once(&vmw->drm,
> +		      "vmwgfx is running on an unknown architecture.");
> +	return false;
> +#endif
> +}
> +
>  /**
>   * __vmw_svga_enable - Enable SVGA mode, FIFO and use of VRAM.
>   *
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> index fb8f0c0642c0..3810a9984a7f 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> @@ -773,6 +773,7 @@ static inline u32 vmw_max_num_uavs(struct vmw_private *dev_priv)
>  
>  extern void vmw_svga_enable(struct vmw_private *dev_priv);
>  extern void vmw_svga_disable(struct vmw_private *dev_priv);
> +bool vmwgfx_supported(struct vmw_private *vmw);
>  
>  
>  /**
> @@ -1358,6 +1359,7 @@ int vmw_bo_cpu_blit(struct ttm_buffer_object *dst,
>  		    struct vmw_diff_cpy *diff);
>  
>  /* Host messaging -vmwgfx_msg.c: */
> +void vmw_disable_backdoor(void);
>  int vmw_host_get_guestinfo(const char *guest_info_param,
>  			   char *buffer, size_t *length);
>  __printf(1, 2) int vmw_host_printf(const char *fmt, ...);
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c b/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
> index ca1a3fe44fa5..2651fe0ef518 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
> @@ -1179,3 +1179,12 @@ int vmw_mksstat_remove_ioctl(struct drm_device *dev, void *data,
>  
>  	return -EAGAIN;
>  }
> +
> +/**
> + * vmw_disable_backdoor: Disables all backdoor communication
> + * with the hypervisor.
> + */
> +void vmw_disable_backdoor(void)
> +{
> +	vmw_msg_enabled = 0;
> +}


LGTM

Reviewed-by: Maaz Mombasawala <mombasawalam at vmware.com>

-- 
Maaz Mombasawala (VMware) <maazm at fastmail.com>