On 2024/4/28 14:45, Tian, Kevin wrote:
From: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx> Sent: Sunday, April 28, 2024 11:20 AM A kernel command called igfx_off was introduced in commit <ba39592764ed> ("Intel IOMMU: Intel IOMMU driver"). This command allows the user to disable the IOMMU dedicated to SOC-integrated graphic devices. Commit <9452618e7462> ("iommu/intel: disable DMAR for g4x integrated gfx") used this mechanism to disable the graphic-dedicated IOMMU for some problematic devices. Later, more problematic graphic devices were added to the list by commit <1f76249cc3beb> ("iommu/vt-d: Declare Broadwell igfx dmar support snafu"). On the other hand, commit <19943b0e30b05> ("intel-iommu: Unify hardware and software passthrough support") uses the identity domain for graphic devices if CONFIG_DMAR_BROKEN_GFX_WA is selected. + if (iommu_pass_through) + iommu_identity_mapping = 1; +#ifdef CONFIG_DMAR_BROKEN_GFX_WA + else + iommu_identity_mapping = 2; +#endif ... static int iommu_should_identity_map(struct pci_dev *pdev, int startup) { + if (iommu_identity_mapping == 2) + return IS_GFX_DEVICE(pdev); ... In the following driver evolution, CONFIG_DMAR_BROKEN_GFX_WA and quirk_iommu_igfx() are mixed together, causing confusion in the driver's device_def_domain_type callback. On one hand, dmar_map_gfx is used to turn off the graphic-dedicated IOMMU as a workaround for some buggy hardware; on the other hand, for those graphic devices, IDENTITY mapping is required for the IOMMU core. Commit <4b8d18c0c986> "iommu/vt-d: Remove INTEL_IOMMU_BROKEN_GFX_WA" has removed the CONFIG_DMAR_BROKEN_GFX_WA option, so the IDENTITY_DOMAIN requirement for graphic devices is no longer needed. Therefore, this requirement can be removed from device_def_domain_type() and igfx_off can be made independent. Fixes: 4b8d18c0c986 ("iommu/vt-d: Remove INTEL_IOMMU_BROKEN_GFX_WA") Signed-off-by: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx> --- drivers/iommu/intel/iommu.c | 19 ++++++------------- 1 file changed, 6 insertions(+), 13 deletions(-) diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index fbbf8fda22f3..57a986524502 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -217,12 +217,11 @@ int intel_iommu_sm = IS_ENABLED(CONFIG_INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON); int intel_iommu_enabled = 0; EXPORT_SYMBOL_GPL(intel_iommu_enabled); -static int dmar_map_gfx = 1; static int intel_iommu_superpage = 1; static int iommu_identity_mapping; static int iommu_skip_te_disable; +static int disable_igfx_dedicated_iommu;what about 'no_igfx_iommu"? dedicated is implied for igfx so a shorter name might be slightly better.
I like disable_igfx_iommu more. :-) Best regards, baolu
