[Intel-gfx] [PATCH V5] drm/i915: Disable stolen memory when i915 runs on qemu

[Alex Williamson]

On Wed, 12 Apr 2017 20:20:00 +0800
Xiong Zhang <xiong.y.zhang at intel.com> wrote:

> Stolen memory isn't a standard pci resource and exists in RMRR which has
> identity mapping in iommu table, IGD could access stolen memory in host OS.
> While according to 'commit c875d2c1b808 ("iommu/vt-d: Exclude devices using
> RMRRs from IOMMU API domains")',RMRR isn't supported by kvm, then both EPT
> and guest iommu domain table lack of maaping for stolen memory in kvm IGD
> passthrough environment. If IGD access stolen memory in such environment,
> many iommu exceptions exist in host dmesg and gpu hang exists also.
> DMAR: [DMA Read] Request device [00:02.0] fault addr da012000
> [fault reason 05] PTE Write access is not set
> DMAR: [DMA Read] Request device [00:02.0] fault addr da2df000
> [fault reason 06] PTE Read access is not set
> 
> So stolen memory should be disabled in KVM IGD passthrough environment,
> this patch detects such environment through the existence of qemu emulated 
> isa bridge.
> 
> When the real ISA bridge is also passed through to guest, guest will have
> two isa bridges: emulated and real. Qemu guarantees the busnum:devnum.
> funcnum of emulated isa bridge is always less than the real one. Then
> emulated isa bridge is always detected first by pci_get_class(ISA). So
> stolen memory will be disabled in this case also.

Where does QEMU make this guarantee or any sort of guarantee wrt the
ISA bridge?  Thanks,

Alex
 
> Stolen memory exists in kernel for a long time, but this patch depends
> on INTEL_PCH_QEMU_DEVICE_ID_TYPE which was introduced in v4.5 kernel,
> so this patch should be backported into v4.5 kernel and above.
> 
> v2:GVT-g may run in non qemu (Zhenyu)
> v3:Make commit message clear (Daniel)
> v4:Fix typo
> v5:Exclude P2X as it is used for VMware (Joonas)
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99028
> 
> Signed-off-by: Xiong Zhang <xiong.y.zhang at intel.com>
> Reviewed-by: Zhenyu Wang <zhenyuw at linux.intel.com>
> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: stable at vger.kernel.org
> ---
>  drivers/gpu/drm/i915/i915_drv.c        | 5 +++++
>  drivers/gpu/drm/i915/i915_drv.h        | 1 +
>  drivers/gpu/drm/i915/i915_gem_stolen.c | 4 ++--
>  3 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 6d9944a..0d3c395 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -223,6 +223,11 @@ static void intel_detect_pch(struct drm_i915_private *dev_priv)
>  					    PCI_SUBVENDOR_ID_REDHAT_QUMRANET &&
>  				    pch->subsystem_device ==
>  					    PCI_SUBDEVICE_ID_QEMU)) {
> +				/*
> +				 * P2X is used for VMware, exclude it
> +				 */
> +				if (id != INTEL_PCH_P2X_DEVICE_ID_TYPE)
> +					dev_priv->run_on_qemu = true;
>  				dev_priv->pch_type =
>  					intel_virt_detect_pch(dev_priv);
>  			} else
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 2911c49..c87150e 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2152,6 +2152,7 @@ struct drm_i915_private {
>  	struct intel_uncore uncore;
>  
>  	struct i915_virtual_gpu vgpu;
> +	bool run_on_qemu;
>  
>  	struct intel_gvt *gvt;
>  
> diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
> index f3abdc2..6a011b0 100644
> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
> @@ -409,8 +409,8 @@ int i915_gem_init_stolen(struct drm_i915_private *dev_priv)
>  
>  	mutex_init(&dev_priv->mm.stolen_lock);
>  
> -	if (intel_vgpu_active(dev_priv)) {
> -		DRM_INFO("iGVT-g active, disabling use of stolen memory\n");
> +	if (dev_priv->run_on_qemu || intel_vgpu_active(dev_priv)) {
> +		DRM_INFO("Running in guest, disabling use of stolen memory\n");
>  		return 0;
>  	}
>