> -----Original Message-----
> From: platform-driver-x86-owner@xxxxxxxxxxxxxxx <platform-driver-x86-
> owner@xxxxxxxxxxxxxxx> On Behalf Of Szabolcs Fruhwald
> Sent: Wednesday, January 23, 2019 5:02 PM
> To: Stuart Hayes
> Cc: platform-driver-x86@xxxxxxxxxxxxxxx; Szabolcs Fruhwald
> Subject: [PATCH] dcdbas: Fix Intel-IOMMU domain allocation failure
>
>
> [EXTERNAL EMAIL]
>
> On Dell systems with intel_iommu enabled, dcdbas platform driver's DMA
> calls fail with ENOMEM / "DMAR: Allocating domain for dcdbas failed".
As a curiosity was this from manually turning on IOMMU or the automatic IOMMU
enablement caused by 89a6079df791aeace2044ea93be1b397195824ec?
>
> This is because the intel-iommu driver only supports PCI bus / devices,
> therefore it is not (yet) possible to properly allocate and attach iommu
> group/domain and attach devices with no pci parent devices.
>
> This workaround is forcing the intel_iommu implementation to use identity
> mapping for this device, using the DUMMY_DEVICE_DOMAIN_INFO constant value
> defined and used in intel-iommu.c.
I would think it makes sense to export this out to a common include that both files can
use if it's using the same constant value as drivers/iommu/intel-iommu.c
At least to me it seems likely that dcdbas is just one of the first drivers that will cause this.
>
> Signed-off-by: Szabolcs Fruhwald <sfruhwald@xxxxxxxxxx>
> ---
> drivers/platform/x86/dcdbas.c | 5 +++++
> drivers/platform/x86/dcdbas.h | 2 +-
> 2 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/platform/x86/dcdbas.c b/drivers/platform/x86/dcdbas.c
> index 88bd7efafe14..a5d6bb1bc590 100644
> --- a/drivers/platform/x86/dcdbas.c
> +++ b/drivers/platform/x86/dcdbas.c
> @@ -652,6 +652,11 @@ static int dcdbas_probe(struct platform_device *dev)
>
> dcdbas_pdev = dev;
>
> + /* Intel-IOMMU workaround: platform-bus unsupported, force ID-mapping
> */
> + #if IS_ENABLED(CONFIG_IOMMU_API) &&
> defined(CONFIG_INTEL_IOMMU)
> + dev->dev.archdata.iommu = INTEL_IOMMU_DUMMY_DOMAIN;
> + #endif
> +
> /* Check if ACPI WSMT table specifies protected SMI buffer address */
> error = dcdbas_check_wsmt();
> if (error < 0)
> diff --git a/drivers/platform/x86/dcdbas.h b/drivers/platform/x86/dcdbas.h
> index 52729a494b00..373eb277933a 100644
> --- a/drivers/platform/x86/dcdbas.h
> +++ b/drivers/platform/x86/dcdbas.h
> @@ -54,6 +54,7 @@
>
> #define SMI_CMD_MAGIC (0x534D4931)
> #define SMM_EPS_SIG "$SCB"
> +#define INTEL_IOMMU_DUMMY_DOMAIN ((void *)-1)
>
> #define DCDBAS_DEV_ATTR_RW(_name) \
> DEVICE_ATTR(_name,0600,_name##_show,_name##_store);
> @@ -114,4 +115,3 @@ struct smm_eps_table {
> } __packed;
>
> #endif /* _DCDBAS_H_ */
> -
> --
> 2.20.1.321.g9e740568ce-goog
