iommu, thunderbolt: Make iommu_dma_protection more accurate
Subsystems (5)
Robin Murphy
reviewerv4 cover iommu, thunderbolt: Make iommu_dma_protection more accurate
Hi all,
As promised, here's the really-actually-final version, cleaning up the new interface in patch #1 to not introduce the new parameter before it's ready, and rebased to make sure it correctly applies on -rc3.
Thanks,
Robin.
Mario Limonciello (1):
iommu/amd: Indicate whether DMA remap support is enabled
Robin Murphy (3):
iommu: Introduce device_iommu_capable()
iommu: Add capability for pre-boot DMA protection
thunderbolt: Make iommu_dma_protection more accurate
drivers/iommu/amd/amd_iommu_types.h | 4 +++ drivers/iommu/amd/init.c | 3 ++ drivers/iommu/amd/iommu.c | 2 ++ drivers/iommu/intel/iommu.c | 2 ++ drivers/iommu/iommu.c | 23 +++++++++++++++ drivers/thunderbolt/domain.c | 12 ++------ drivers/thunderbolt/nhi.c | 44 +++++++++++++++++++++++++++++ include/linux/iommu.h | 8 ++++++ include/linux/thunderbolt.h | 2 ++ 9 files changed, 91 insertions(+), 9 deletions(-)
Signature · 6 lines
2.35.3.dirty _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
Robin Murphy
reviewerPATCH v4 1/4 iommu: Introduce device_iommu_capable()
iommu_capable() only really works for systems where all IOMMU instances are completely homogeneous, and all devices are IOMMU-mapped. Implement the new variant which will be able to give a more accurate answer for whichever device the caller is actually interested in, and even more so once all the external users have been converted and we can reliably pass the device pointer through the internal driver interface too.
---
v4: Hold off changing the internal callback interface for now
drivers/iommu/iommu.c | 23 +++++++++++++++++++++++ include/linux/iommu.h | 6 ++++++ 2 files changed, 29 insertions(+)
drivers/iommu/iommu.c +23 -0
@@ -1906,6 +1906,29 @@ bool iommu_present(struct bus_type *bus) }EXPORT_SYMBOL_GPL (iommu_present); +/** +* device_iommu_capable() - check for a general IOMMU capability +* @dev: device to which the capability would be relevant, if available +* @cap: IOMMU capability +* +* Return: true if an IOMMU is present and supports the given capability +* for the given device, otherwise false. +*/ +bool device_iommu_capable (struct device *dev,enum iommu_cap cap) +{ +const struct iommu_ops *ops; + +if (!dev->iommu || !dev->iommu->iommu_dev) +return false; + + ops =dev_iommu_ops (dev); +if (!ops->capable) +return false; + +return ops->capable (cap); +} +EXPORT_SYMBOL_GPL (device_iommu_capable); +bool iommu_capable (struct bus_type *bus,enum iommu_cap cap) {if (!bus->iommu_ops || !bus->iommu_ops->capable)
include/linux/iommu.h +6 -0
@@ -417,6 +417,7 @@ static inline const struct iommu_ops *dev_iommu_ops(struct device *dev)extern int bus_set_iommu (struct bus_type *bus,const struct iommu_ops *ops);extern int bus_iommu_probe (struct bus_type *bus);extern bool iommu_present (struct bus_type *bus); +extern bool device_iommu_capable (struct device *dev,enum iommu_cap cap);extern bool iommu_capable (struct bus_type *bus,enum iommu_cap cap);extern struct iommu_domain *iommu_domain_alloc (struct bus_type *bus);extern struct iommu_group *iommu_group_get_by_id (int id);
@@ -689,6 +690,11 @@ static inline bool iommu_present(struct bus_type *bus)return false; } +static inline bool device_iommu_capable (struct device *dev,enum iommu_cap cap) +{ +return false; +} +static inline bool iommu_capable (struct bus_type *bus,enum iommu_cap cap) {return false;
Signature · 1 line
2.35.3.dirty
Robin Murphy
reviewerPATCH v4 2/4 iommu: Add capability for pre-boot DMA protection
In reply to Robin MurphyVT-d's dmar_platform_optin() actually represents a combination of properties fairly well standardised by Microsoft as "Pre-boot DMA Protection" and "Kernel DMA Protection"[1]. As such, we can provide interested consumers with an abstracted capability rather than driver-specific interfaces that won't scale. We name it for the former aspect since that's what external callers are most likely to be interested in; the latter is for the IOMMU layer to handle itself.
---
v4: No change
drivers/iommu/intel/iommu.c | 2 ++ include/linux/iommu.h | 2 ++ 2 files changed, 4 insertions(+)
drivers/iommu/intel/iommu.c +2 -0
@@ -4551,6 +4551,8 @@ static bool intel_iommu_capable(enum iommu_cap cap)return domain_update_iommu_snooping (NULL );if (cap ==IOMMU_CAP_INTR_REMAP )return irq_remapping_enabled ==1 ; +if (cap ==IOMMU_CAP_PRE_BOOT_PROTECTION ) +return dmar_platform_optin ();return false; }
include/linux/iommu.h +2 -0
@@ -107,6 +107,8 @@ enum iommu_cap {transactions */ IOMMU_CAP_INTR_REMAP ,/* IOMMU supports interrupt isolation */ IOMMU_CAP_NOEXEC ,/* IOMMU_NOEXEC flag */ + IOMMU_CAP_PRE_BOOT_PROTECTION, /* Firmware says it used the IOMMU for + DMA protection and we should too */ };/* These are the possible reserved region types */
Signature · 1 line
2.35.3.dirty
Robin Murphy
reviewerPATCH v4 3/4 thunderbolt: Make iommu_dma_protection more accurate
In reply to Robin MurphyBetween me trying to get rid of iommu_present() and Mario wanting to support the AMD equivalent of DMAR_PLATFORM_OPT_IN, scrutiny has shown that the iommu_dma_protection attribute is being far too optimistic. Even if an IOMMU might be present for some PCI segment in the system, that doesn't necessarily mean it provides translation for the device(s) we care about. Furthermore, all that DMAR_PLATFORM_OPT_IN really does is tell us that memory was protected before the kernel was loaded, and prevent the user from disabling the intel-iommu driver entirely. While that lets us assume kernel integrity, what matters for actual runtime DMA protection is whether we trust individual devices, based on the "external facing" property that we expect firmware to describe for Thunderbolt ports.
It's proven challenging to determine the appropriate ports accurately given the variety of possible topologies, so while still not getting a perfect answer, by putting enough faith in firmware we can at least get a good bit closer. If we can see that any device near a Thunderbolt NHI has all the requisites for Kernel DMA Protection, chances are that it *is* a relevant port, but moreover that implies that firmware is playing the game overall, so we'll use that to assume that all Thunderbolt ports should be correctly marked and thus will end up fully protected.
---
v4: No change
drivers/thunderbolt/domain.c | 12 +++------- drivers/thunderbolt/nhi.c | 44 ++++++++++++++++++++++++++++++++++++ include/linux/thunderbolt.h | 2 ++ 3 files changed, 49 insertions(+), 9 deletions(-)
drivers/thunderbolt/domain.c +3 -9
@@ -7,9 +7,7 @@*/ #include <linux/device.h> -#include <linux/dmar.h> #include <linux/idr.h> -#include <linux/iommu.h> #include <linux/module.h> #include <linux/pm_runtime.h> #include <linux/slab.h>
@@ -257,13 +255,9 @@ static ssize_t iommu_dma_protection_show(struct device *dev,struct device_attribute *attr, char *buf) { -/* -* Kernel DMA protection is a feature where Thunderbolt security is -* handled natively using IOMMU. It is enabled when IOMMU is -* enabled and ACPI DMAR table has DMAR_PLATFORM_OPT_IN set. -*/ -return sprintf (buf,"%d\n" , -iommu_present (&pci_bus_type) &&dmar_platform_optin ()); + struct tb *tb = container_of(dev, struct tb, dev); + +return sysfs_emit (buf,"%d\n" , tb->nhi->iommu_dma_protection); }static DEVICE_ATTR_RO (iommu_dma_protection);
drivers/thunderbolt/nhi.c +44 -0
65 lines not on this page · raw message
include/linux/thunderbolt.h +2 -0
@@ -465,6 +465,7 @@ static inline struct tb_xdomain *tb_service_parent(struct tb_service *svc)* @msix_ida: Used to allocate MSI-X vectors for rings * @going_away: The host controller device is about to disappear so when * this flag is set, avoid touching the hardware anymore. +* @iommu_dma_protection: An IOMMU will isolate external-facing ports. * @interrupt_work: Work scheduled to handle ring interrupt when no * MSI-X is used. * @hop_count: Number of rings (end point hops) supported by NHI.
@@ -479,6 +480,7 @@ struct tb_nhi {struct tb_ring **rx_rings;struct ida msix_ida;bool going_away; +bool iommu_dma_protection;struct work_struct interrupt_work;u32 hop_count;unsigned long quirks;
Signature · 1 line
2.35.3.dirty
Robin Murphy
reviewerPATCH v4 4/4 iommu/amd: Indicate whether DMA remap support is enabled
In reply to Robin MurphyFrom: Mario Limonciello <[email protected]>
Bit 1 of the IVFS IVInfo field indicates that IOMMU has been used for pre-boot DMA protection.
Export this capability to allow other places in the kernel to be able to check for it on AMD systems.
---
v4: No change
drivers/iommu/amd/amd_iommu_types.h | 4 ++++ drivers/iommu/amd/init.c | 3 +++ drivers/iommu/amd/iommu.c | 2 ++ 3 files changed, 9 insertions(+)
drivers/iommu/amd/amd_iommu_types.h +4 -0
@@ -407,6 +407,7 @@/* IOMMU IVINFO */ #define IOMMU_IVINFO_OFFSET 36#define IOMMU_IVINFO_EFRSUP BIT(0) +#define IOMMU_IVINFO_DMA_REMAP BIT(1)/* IOMMU Feature Reporting Field (for IVHD type 10h */ #define IOMMU_FEAT_GASUP_SHIFT 6
@@ -449,6 +450,9 @@ extern struct irq_remap_table **irq_lookup_table;/* Interrupt remapping feature used? */ extern bool amd_iommu_irq_remap; +/* IVRS indicates that pre-boot remapping was enabled */ +extern bool amdr_ivrs_remap_support; +/* kmem_cache to get tables with 128 byte alignement */ extern struct kmem_cache *amd_iommu_irq_cache;
drivers/iommu/amd/init.c +3 -0
@@ -182,6 +182,7 @@ u32 amd_iommu_max_pasid __read_mostly = ~0;bool amd_iommu_v2_present__read_mostly ;static bool amd_iommu_pc_present__read_mostly ; +bool amdr_ivrs_remap_support__read_mostly ;bool amd_iommu_force_isolation__read_mostly ;
@@ -326,6 +327,8 @@ static void __init early_iommu_features_init(struct amd_iommu *iommu, {if (amd_iommu_ivinfo &IOMMU_IVINFO_EFRSUP ) iommu->features = h->efr_reg; +if (amd_iommu_ivinfo &IOMMU_IVINFO_DMA_REMAP ) + amdr_ivrs_remap_support = true; }/* Access to l1 and l2 indexed register spaces */
drivers/iommu/amd/iommu.c +2 -0
@@ -2162,6 +2162,8 @@ static bool amd_iommu_capable(enum iommu_cap cap)return (irq_remapping_enabled ==1 );case IOMMU_CAP_NOEXEC :return false; +case IOMMU_CAP_PRE_BOOT_PROTECTION : +return amdr_ivrs_remap_support;default :break ; }
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2.35.3.dirty _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu