* [PATCH v2 1/2] arm64: Add override for MMFR1.HAFDBS
2026-07-23 14:19 [PATCH v2 0/2] iommu/arm-smmu-v3: Fix SVA vs. HAFT issues Robin Murphy
@ 2026-07-23 14:19 ` Robin Murphy
2026-07-23 14:19 ` [PATCH v2 2/2] iommu/arm-smmu-v3: Add HAFT support for SVA Robin Murphy
1 sibling, 0 replies; 3+ messages in thread
From: Robin Murphy @ 2026-07-23 14:19 UTC (permalink / raw)
To: will, catalin.marinas, joro; +Cc: jpb, jgg, iommu, linux-arm-kernel
In general it might be nice to have the ability to disable hardware
access/dirty bit management for debugging or performance comparison
purposes without having to rebuild the kernel. However once FEAT_HAFT
comes into the picture we also start to have a real functional concern
where the decision to use HAFT based on the boot CPUs can prevent SVA
or late-onlining if SMMUs/CPUs are later found to lack HAFT support.
To that end, add the appropriate MMFR1 override, with an easy "nohaft"
alias for the significant case, partly since the feature/field naming
isn't the most obvious, but also so it could potentially be redirected
if someone wanted to attempt a higher-level means of turning off just
HAFT usage independently from FEAT_HDBSS in future.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
v2: New
OK, turns out this was actually incredibly easy, thanks Marc for
making the framework so idiot-proof!
Documentation/admin-guide/kernel-parameters.txt | 3 +++
arch/arm64/kernel/pi/idreg-override.c | 2 ++
2 files changed, 5 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index b5493a7f8f22..7f23e5b8dc44 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -565,6 +565,9 @@ Kernel parameters
arm64.nogcs [ARM64] Unconditionally disable Guarded Control Stack
support
+ arm64.nohaft [ARM64] Unconditionally disable Hardware managed Access
+ Flag for Table descriptors support
+
arm64.nomops [ARM64] Unconditionally disable Memory Copy and Memory
Set instructions support
diff --git a/arch/arm64/kernel/pi/idreg-override.c b/arch/arm64/kernel/pi/idreg-override.c
index bc57b290e5e7..0e051fec5afe 100644
--- a/arch/arm64/kernel/pi/idreg-override.c
+++ b/arch/arm64/kernel/pi/idreg-override.c
@@ -64,6 +64,7 @@ static const struct ftr_set_desc mmfr1 __prel64_initconst = {
.override = &id_aa64mmfr1_override,
.fields = {
FIELD("vh", ID_AA64MMFR1_EL1_VH_SHIFT, mmfr1_vh_filter),
+ FIELD("hafdbs", ID_AA64MMFR1_EL1_HAFDBS_SHIFT, NULL),
{}
},
};
@@ -246,6 +247,7 @@ static const struct {
{ "arm64.nomte", "id_aa64pfr1.mte=0" },
{ "nokaslr", "arm64_sw.nokaslr=1" },
{ "rodata=off", "arm64_sw.rodataoff=1" },
+ { "arm64.nohaft", "id_aa64mmfr1.hafdbs=2" },
{ "arm64.nolva", "id_aa64mmfr2.varange=0" },
{ "arm64.no32bit_el0", "id_aa64pfr0.el0=1" },
{ "arm64.nompam", "id_aa64pfr0.mpam=0 id_aa64pfr1.mpam_frac=0" },
--
2.54.0.dirty
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH v2 2/2] iommu/arm-smmu-v3: Add HAFT support for SVA
2026-07-23 14:19 [PATCH v2 0/2] iommu/arm-smmu-v3: Fix SVA vs. HAFT issues Robin Murphy
2026-07-23 14:19 ` [PATCH v2 1/2] arm64: Add override for MMFR1.HAFDBS Robin Murphy
@ 2026-07-23 14:19 ` Robin Murphy
1 sibling, 0 replies; 3+ messages in thread
From: Robin Murphy @ 2026-07-23 14:19 UTC (permalink / raw)
To: will, catalin.marinas, joro; +Cc: jpb, jgg, iommu, linux-arm-kernel
Since table access flags cannot be software-managed, if process
pagetables are using HAFT then SVA must require the SMMU to support and
enable it too, otherwise page aging is liable to get out of whack.
Cc: <stable@vger.kernel.org>
Fixes: 62df5870ebf7 ("arm64: Enable ARCH_HAS_NONLEAF_PMD_YOUNG")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
v2: Update IORT override warning condition correctly
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 5 +++++
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 9 ++++++++-
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 3 +++
3 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
index 1ed8a6f29dc4..ef11e9493f93 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
@@ -102,6 +102,8 @@ void arm_smmu_make_sva_cd(struct arm_smmu_cd *target,
target->data[0] |= cpu_to_le64(CTXDESC_CD_0_TCR_HA);
if (master->smmu->features & ARM_SMMU_FEAT_HD)
target->data[0] |= cpu_to_le64(CTXDESC_CD_0_TCR_HD);
+ if (master->smmu->features & ARM_SMMU_FEAT_HAFT && system_supports_haft())
+ target->data[1] |= cpu_to_le64(CTXDESC_CD_1_HAFT);
} else {
target->data[0] |= cpu_to_le64(CTXDESC_CD_0_TCR_EPD0);
@@ -211,6 +213,9 @@ bool arm_smmu_sva_supported(struct arm_smmu_device *smmu)
if (system_supports_bbml2_noabort())
feat_mask |= ARM_SMMU_FEAT_BBML2;
+ if (system_supports_haft())
+ feat_mask |= ARM_SMMU_FEAT_HAFT;
+
if ((smmu->features & feat_mask) != feat_mask)
return false;
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index a10affb483a4..14e5b3f08962 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -4921,10 +4921,14 @@ static void arm_smmu_device_iidr_probe(struct arm_smmu_device *smmu)
static void arm_smmu_get_httu(struct arm_smmu_device *smmu, u32 reg)
{
- u32 fw_features = smmu->features & (ARM_SMMU_FEAT_HA | ARM_SMMU_FEAT_HD);
+ u32 fw_features = smmu->features & (ARM_SMMU_FEAT_HA | ARM_SMMU_FEAT_HD |
+ ARM_SMMU_FEAT_HAFT);
u32 hw_features = 0;
switch (FIELD_GET(IDR0_HTTU, reg)) {
+ case IDR0_HTTU_ACCESS_DIRTY_HAFT:
+ hw_features |= ARM_SMMU_FEAT_HAFT;
+ fallthrough;
case IDR0_HTTU_ACCESS_DIRTY:
hw_features |= ARM_SMMU_FEAT_HD;
fallthrough;
@@ -5256,6 +5260,9 @@ static int arm_smmu_device_acpi_probe(struct platform_device *pdev,
smmu->features |= ARM_SMMU_FEAT_COHERENCY;
switch (FIELD_GET(ACPI_IORT_SMMU_V3_HTTU_OVERRIDE, iort_smmu->flags)) {
+ case IDR0_HTTU_ACCESS_DIRTY_HAFT:
+ smmu->features |= ARM_SMMU_FEAT_HAFT;
+ fallthrough;
case IDR0_HTTU_ACCESS_DIRTY:
smmu->features |= ARM_SMMU_FEAT_HD;
fallthrough;
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index c909c9a88538..61a7df5afb99 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -40,6 +40,7 @@ struct arm_vsmmu;
#define IDR0_HTTU GENMASK(7, 6)
#define IDR0_HTTU_ACCESS 1
#define IDR0_HTTU_ACCESS_DIRTY 2
+#define IDR0_HTTU_ACCESS_DIRTY_HAFT 3
#define IDR0_COHACC (1 << 4)
#define IDR0_TTF GENMASK(3, 2)
#define IDR0_TTF_AARCH64 2
@@ -369,6 +370,7 @@ static inline unsigned int arm_smmu_cdtab_l2_idx(unsigned int ssid)
#define CTXDESC_CD_0_ASET (1UL << 47)
#define CTXDESC_CD_0_ASID GENMASK_ULL(63, 48)
+#define CTXDESC_CD_1_HAFT (1UL << 3)
#define CTXDESC_CD_1_TTB0_MASK GENMASK_ULL(51, 4)
/*
@@ -921,6 +923,7 @@ struct arm_smmu_device {
#define ARM_SMMU_FEAT_HD (1 << 22)
#define ARM_SMMU_FEAT_S2FWB (1 << 23)
#define ARM_SMMU_FEAT_BBML2 (1 << 24)
+#define ARM_SMMU_FEAT_HAFT (1 << 25)
u32 features;
#define ARM_SMMU_OPT_SKIP_PREFETCH (1 << 0)
--
2.54.0.dirty
^ permalink raw reply related [flat|nested] 3+ messages in thread