Re: [Intel-gfx] [PATCH v1] vfio/pci: Refine Intel IGD OpRegion support

From: Alex Williamson <alex.williamson@redhat.com>
To: Fred Gao <fred.gao@intel.com>
Cc: Hang Yuan <hang.yuan@linux.intel.com>,
	kvm@vger.kernel.org, intel-gfx@lists.freedesktop.org,
	Lucas De Marchi <lucas.demarchi@intel.com>
Subject: Re: [Intel-gfx] [PATCH v1] vfio/pci: Refine Intel IGD OpRegion support
Date: Thu, 9 Jul 2020 09:27:30 -0600	[thread overview]
Message-ID: <20200709092730.01128671@x1.home> (raw)
In-Reply-To: <20200709173707.29808-1-fred.gao@intel.com>

On Fri, 10 Jul 2020 01:37:07 +0800
Fred Gao <fred.gao@intel.com> wrote:

> Bypass the IGD initialization for Intel's dgfx devices with own expansion
> ROM and the host/LPC bridge config space are no longer accessed.
> 
> Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
> Cc: Xiong Zhang <xiong.y.zhang@intel.com>
> Cc: Hang Yuan <hang.yuan@linux.intel.com>
> Cc: Stuart Summers <stuart.summers@intel.com>
> Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
> Signed-off-by: Fred Gao <fred.gao@intel.com>
> ---
>  drivers/vfio/pci/vfio_pci.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index f634c81998bb..0f4a34849836 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -28,6 +28,8 @@
>  #include <linux/nospec.h>
>  #include <linux/sched/mm.h>
>  
> +#include <drm/i915_pciids.h>
> +
>  #include "vfio_pci_private.h"
>  
>  #define DRIVER_VERSION  "0.2"
> @@ -60,6 +62,12 @@ module_param(enable_sriov, bool, 0644);
>  MODULE_PARM_DESC(enable_sriov, "Enable support for SR-IOV configuration.  Enabling SR-IOV on a PF typically requires support of the userspace PF driver, enabling VFs without such support may result in non-functional VFs or PF.");
>  #endif
>  
> +/* Intel's dgfx is not IGD, so don't handle them the same way */
> +static const struct pci_device_id intel_dgfx_pciids[] = {
> +	INTEL_DG1_IDS(0),
> +	{ }
> +};
> +
>  static inline bool vfio_vga_disabled(void)
>  {
>  #ifdef CONFIG_VFIO_PCI_VGA
> @@ -339,7 +347,8 @@ static int vfio_pci_enable(struct vfio_pci_device *vdev)
>  
>  	if (vfio_pci_is_vga(pdev) &&
>  	    pdev->vendor == PCI_VENDOR_ID_INTEL &&
> -	    IS_ENABLED(CONFIG_VFIO_PCI_IGD)) {
> +	    IS_ENABLED(CONFIG_VFIO_PCI_IGD) &&
> +	    !pci_match_id(intel_dgfx_pciids, pdev)) {
>  		ret = vfio_pci_igd_init(vdev);
>  		if (ret) {
>  			pci_warn(pdev, "Failed to setup Intel IGD regions\n");

Do we need to maintain specific IDs or could we simply test whether the
device is on the root bus to determine if it is integrated or discrete?
A discrete device should be connected to a downstream port rather than
appear on the root bus.  Thanks,

Alex

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