Commit e5e04d05 authored by Lu Baolu's avatar Lu Baolu Committed by Joerg Roedel
Browse files

iommu/vt-d: Check whether device requires bounce buffer 



This adds a helper to check whether a device needs to
use bounce buffer. It also provides a boot time option
to disable the bounce buffer. Users can use this to
prevent the iommu driver from using the bounce buffer
for performance gain.

Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: default avatarLu Baolu <baolu.lu@linux.intel.com>
Tested-by: default avatarXu Pengfei <pengfei.xu@intel.com>
Tested-by: default avatarMika Westerberg <mika.westerberg@intel.com>
Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
parent 3fc1ca00

Documentation/admin-guide/kernel-parameters.txt

+5 −0
Original line number Original line Diff line number Diff line
@@ -1732,6 +1732,11 @@ 
			Note that using this option lowers the security

			Note that using this option lowers the security

			provided by tboot because it makes the system

			provided by tboot because it makes the system

			vulnerable to DMA attacks.

			vulnerable to DMA attacks.

		nobounce [Default off]

			Disable bounce buffer for unstrusted devices such as

			the Thunderbolt devices. This will treat the untrusted

			devices as the trusted ones, hence might expose security

			risks of DMA attacks.





	intel_idle.max_cstate=	[KNL,HW,ACPI,X86]

	intel_idle.max_cstate=	[KNL,HW,ACPI,X86]

			0	disables intel_idle and fall back on acpi_idle.

			0	disables intel_idle and fall back on acpi_idle.

drivers/iommu/intel-iommu.c

+7 −0
Original line number Original line Diff line number Diff line
@@ -360,6 +360,7 @@ static int dmar_forcedac; 
static int intel_iommu_strict;

static int intel_iommu_strict;

static int intel_iommu_superpage = 1;

static int intel_iommu_superpage = 1;

static int iommu_identity_mapping;

static int iommu_identity_mapping;

static int intel_no_bounce;





#define IDENTMAP_ALL		1

#define IDENTMAP_ALL		1

#define IDENTMAP_GFX		2

#define IDENTMAP_GFX		2
@@ -373,6 +374,9 @@ EXPORT_SYMBOL_GPL(intel_iommu_gfx_mapped); 
static DEFINE_SPINLOCK(device_domain_lock);

static DEFINE_SPINLOCK(device_domain_lock);

static LIST_HEAD(device_domain_list);

static LIST_HEAD(device_domain_list);





#define device_needs_bounce(d) (!intel_no_bounce && dev_is_pci(d) &&	\

				to_pci_dev(d)->untrusted)



/*

/*

 * Iterate over elements in device_domain_list and call the specified

 * Iterate over elements in device_domain_list and call the specified

 * callback @fn against each element.

 * callback @fn against each element.
@@ -455,6 +459,9 @@ static int __init intel_iommu_setup(char *str) 
			printk(KERN_INFO

			printk(KERN_INFO

				"Intel-IOMMU: not forcing on after tboot. This could expose security risk for tboot\n");

				"Intel-IOMMU: not forcing on after tboot. This could expose security risk for tboot\n");

			intel_iommu_tboot_noforce = 1;

			intel_iommu_tboot_noforce = 1;

		} else if (!strncmp(str, "nobounce", 8)) {

			pr_info("Intel-IOMMU: No bounce buffer. This could expose security risks of DMA attacks\n");

			intel_no_bounce = 1;

		}

		}





		str += strcspn(str, ",");

		str += strcspn(str, ",");

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