On 2021/11/10 20:08, Tvrtko Ursulin wrote:
On 10/11/2021 12:04, Lu Baolu wrote:
On 2021/11/10 17:30, Tvrtko Ursulin wrote:
On 10/11/2021 07:12, Lu Baolu wrote:
Hi Tvrtko,
On 2021/11/9 20:17, Tvrtko Ursulin wrote:
From: Tvrtko Ursulintvrtko.ursulin@intel.com
On igfx + dgfx setups, it appears that intel_iommu=igfx_off option only disables the igfx iommu. Stop relying on global intel_iommu_gfx_mapped and probe presence of iommu domain per device to accurately reflect its status.
Signed-off-by: Tvrtko Ursulintvrtko.ursulin@intel.com Cc: Lu Baolubaolu.lu@linux.intel.com
Baolu, is my understanding here correct? Maybe I am confused by both intel_iommu_gfx_mapped and dmar_map_gfx being globals in the intel_iommu driver. But it certainly appears the setup can assign some iommu ops (and assign the discrete i915 to iommu group) when those two are set to off.
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index e967cd08f23e..9fb38a54f1fe 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -1763,26 +1763,27 @@ static inline bool run_as_guest(void) #define HAS_D12_PLANE_MINIMIZATION(dev_priv) (IS_ROCKETLAKE(dev_priv) || \ IS_ALDERLAKE_S(dev_priv))
-static inline bool intel_vtd_active(void) +static inline bool intel_vtd_active(struct drm_i915_private *i915) { -#ifdef CONFIG_INTEL_IOMMU - if (intel_iommu_gfx_mapped) + if (iommu_get_domain_for_dev(i915->drm.dev)) return true; -#endif
/* Running as a guest, we assume the host is enforcing VT'd */ return run_as_guest(); }
Have you verified this change? I am afraid that iommu_get_domain_for_dev() always gets a valid iommu domain even intel_iommu_gfx_mapped == 0.
Yes it seems to work as is:
default:
# grep -i iommu /sys/kernel/debug/dri/*/i915_capabilities /sys/kernel/debug/dri/0/i915_capabilities:iommu: enabled /sys/kernel/debug/dri/1/i915_capabilities:iommu: enabled
intel_iommu=igfx_off:
# grep -i iommu /sys/kernel/debug/dri/*/i915_capabilities /sys/kernel/debug/dri/0/i915_capabilities:iommu: disabled /sys/kernel/debug/dri/1/i915_capabilities:iommu: enabled
On my system dri device 0 is integrated graphics and 1 is discrete.
The drm device 0 has a dedicated iommu. When the user request igfx not mapped, the VT-d implementation will turn it off to save power. But for shared iommu, you definitely will get it enabled.
Sorry I am not following, what exactly do you mean? Is there a platform with integrated graphics without a dedicated iommu, in which case intel_iommu=igfx_off results in intel_iommu_gfx_mapped == 0 and iommu_get_domain_for_dev returning non-NULL?
Your code always work for an igfx with a dedicated iommu. This might be always true on today's platforms. But from driver's point of view, we should not make such assumption.
For example, if the iommu implementation decides not to turn off the graphic iommu (perhaps due to some hw quirk or for graphic virtualization), your code will be broken.
Best regards, baolu