[PATCH RESEND v9 08/13] iommu/arm-smmu-v3: Share process page tables

Jean-Philippe Brucker
2020-08-17T17:22:06Z

With Shared Virtual Addressing (SVA), we need to mirror CPU TTBR, TCR,
MAIR and ASIDs in SMMU contexts. Each SMMU has a single ASID space split
into two sets, shared and private. Shared ASIDs correspond to those
obtained from the arch ASID allocator, and private ASIDs are used for
"classic" map/unmap DMA.

A possible conflict happens when trying to use a shared ASID that has
already been allocated for private use by the SMMU driver. This will be
addressed in a later patch by replacing the private ASID. At the
moment we return -EBUSY.

Each mm_struct shared with the SMMU will have a single context
descriptor. Add a refcount to keep track of this. It will be protected
by the global SVA lock.

Introduce a new arm-smmu-v3-sva.c file and the CONFIG_ARM_SMMU_V3_SVA
option to let users opt in SVA support.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
v9: Move to arm-smmu-v3-sva.c
---
drivers/iommu/Kconfig | 10 ++
drivers/iommu/arm/arm-smmu-v3/Makefile | 5 +-
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 8 ++
.../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 123 ++++++++++++++++++
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 34 ++++-
5 files changed, 172 insertions(+), 8 deletions(-)
create mode 100644 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index fb1787377eb6..b1d592cd9984 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -313,6 +313,16 @@ config ARM_SMMU_V3
Say Y here if your system includes an IOMMU device implementing
the ARM SMMUv3 architecture.

+config ARM_SMMU_V3_SVA
+ bool "Shared Virtual Addressing support for the ARM SMMUv3"
+ depends on ARM_SMMU_V3
+ help
+ Support for sharing process address spaces with devices using the
+ SMMUv3.
+
+ Say Y here if your system supports SVA extensions such as PCIe PASID
+ and PRI.
+
config S390_IOMMU
def_bool y if S390 && PCI
depends on S390 && PCI
diff --git a/drivers/iommu/arm/arm-smmu-v3/Makefile b/drivers/iommu/arm/arm-smmu-v3/Makefile
index 569e24e9f162..54feb1ecccad 100644
--- a/drivers/iommu/arm/arm-smmu-v3/Makefile
+++ b/drivers/iommu/arm/arm-smmu-v3/Makefile
@@ -1,2 +1,5 @@
# SPDX-License-Identifier: GPL-2.0
-obj-$(CONFIG_ARM_SMMU_V3) += arm-smmu-v3.o
+obj-$(CONFIG_ARM_SMMU_V3) += arm_smmu_v3.o
+arm_smmu_v3-objs-y += arm-smmu-v3.o
+arm_smmu_v3-objs-$(CONFIG_ARM_SMMU_V3_SVA) += arm-smmu-v3-sva.o
+arm_smmu_v3-objs := $(arm_smmu_v3-objs-y)
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 51a9ce07b2d6..6b06a6f19604 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -540,6 +540,9 @@ struct arm_smmu_ctx_desc {
u64 ttbr;
u64 tcr;
u64 mair;
+
+ refcount_t refs;
+ struct mm_struct *mm;
};

struct arm_smmu_l1_ctx_desc {
@@ -672,4 +675,9 @@ struct arm_smmu_domain {
spinlock_t devices_lock;
};

+extern struct xarray arm_smmu_asid_xa;
+extern struct mutex arm_smmu_asid_lock;
+
+bool arm_smmu_free_asid(struct arm_smmu_ctx_desc *cd);
+
#endif /* _ARM_SMMU_V3_H */
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
new file mode 100644
index 000000000000..7a4f40565e06
--- /dev/null
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implementation of the IOMMU SVA API for the ARM SMMUv3
+ */
+
+#include <linux/mm.h>
+#include <linux/mmu_context.h>
+#include <linux/slab.h>
+
+#include "arm-smmu-v3.h"
+#include "../../io-pgtable-arm.h"
+
+static struct arm_smmu_ctx_desc *
+arm_smmu_share_asid(struct mm_struct *mm, u16 asid)
+{
+ struct arm_smmu_ctx_desc *cd;
+
+ cd = xa_load(&arm_smmu_asid_xa, asid);
+ if (!cd)
+ return NULL;
+
+ if (cd->mm) {
+ if (WARN_ON(cd->mm != mm))
+ return ERR_PTR(-EINVAL);
+ /* All devices bound to this mm use the same cd struct. */
+ refcount_inc(&cd->refs);
+ return cd;
+ }
+
+ /* Ouch, ASID is already in use for a private cd. */
+ return ERR_PTR(-EBUSY);
+}
+
+__maybe_unused
+static struct arm_smmu_ctx_desc *arm_smmu_alloc_shared_cd(struct mm_struct *mm)
+{
+ u16 asid;
+ int err = 0;
+ u64 tcr, par, reg;
+ struct arm_smmu_ctx_desc *cd;
+ struct arm_smmu_ctx_desc *ret = NULL;
+
+ asid = arm64_mm_context_get(mm);
+ if (!asid)
+ return ERR_PTR(-ESRCH);
+
+ cd = kzalloc(sizeof(*cd), GFP_KERNEL);
+ if (!cd) {
+ err = -ENOMEM;
+ goto out_put_context;
+ }
+
+ refcount_set(&cd->refs, 1);
+
+ mutex_lock(&arm_smmu_asid_lock);
+ ret = arm_smmu_share_asid(mm, asid);
+ if (ret) {
+ mutex_unlock(&arm_smmu_asid_lock);
+ goto out_free_cd;
+ }
+
+ err = xa_insert(&arm_smmu_asid_xa, asid, cd, GFP_KERNEL);
+ mutex_unlock(&arm_smmu_asid_lock);
+
+ if (err)
+ goto out_free_asid;
+
+ tcr = FIELD_PREP(CTXDESC_CD_0_TCR_T0SZ, 64ULL - VA_BITS) |
+ FIELD_PREP(CTXDESC_CD_0_TCR_IRGN0, ARM_LPAE_TCR_RGN_WBWA) |
+ FIELD_PREP(CTXDESC_CD_0_TCR_ORGN0, ARM_LPAE_TCR_RGN_WBWA) |
+ FIELD_PREP(CTXDESC_CD_0_TCR_SH0, ARM_LPAE_TCR_SH_IS) |
+ CTXDESC_CD_0_TCR_EPD1 | CTXDESC_CD_0_AA64;
+
+ switch (PAGE_SIZE) {
+ case SZ_4K:
+ tcr |= FIELD_PREP(CTXDESC_CD_0_TCR_TG0, ARM_LPAE_TCR_TG0_4K);
+ break;
+ case SZ_16K:
+ tcr |= FIELD_PREP(CTXDESC_CD_0_TCR_TG0, ARM_LPAE_TCR_TG0_16K);
+ break;
+ case SZ_64K:
+ tcr |= FIELD_PREP(CTXDESC_CD_0_TCR_TG0, ARM_LPAE_TCR_TG0_64K);
+ break;
+ default:
+ WARN_ON(1);
+ err = -EINVAL;
+ goto out_free_asid;
+ }
+
+ reg = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
+ par = cpuid_feature_extract_unsigned_field(reg, ID_AA64MMFR0_PARANGE_SHIFT);
+ tcr |= FIELD_PREP(CTXDESC_CD_0_TCR_IPS, par);
+
+ cd->ttbr = virt_to_phys(mm->pgd);
+ cd->tcr = tcr;
+ /*
+ * MAIR value is pretty much constant and global, so we can just get it
+ * from the current CPU register
+ */
+ cd->mair = read_sysreg(mair_el1);
+ cd->asid = asid;
+ cd->mm = mm;
+
+ return cd;
+
+out_free_asid:
+ arm_smmu_free_asid(cd);
+out_free_cd:
+ kfree(cd);
+out_put_context:
+ arm64_mm_context_put(mm);
+ return err < 0 ? ERR_PTR(err) : ret;
+}
+
+__maybe_unused
+static void arm_smmu_free_shared_cd(struct arm_smmu_ctx_desc *cd)
+{
+ if (arm_smmu_free_asid(cd)) {
+ /* Unpin ASID */
+ arm64_mm_context_put(cd->mm);
+ kfree(cd);
+ }
+}
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 b2ad5dc73e6a..9e81615744de 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -68,7 +68,8 @@ struct arm_smmu_option_prop {
const char *prop;
};

-static DEFINE_XARRAY_ALLOC1(asid_xa);
+DEFINE_XARRAY_ALLOC1(arm_smmu_asid_xa);
+DEFINE_MUTEX(arm_smmu_asid_lock);

static struct arm_smmu_option_prop arm_smmu_options[] = {
{ ARM_SMMU_OPT_SKIP_PREFETCH, "hisilicon,broken-prefetch-cmd" },
@@ -1004,7 +1005,8 @@ static int arm_smmu_write_ctx_desc(struct arm_smmu_domain *smmu_domain,
#ifdef __BIG_ENDIAN
CTXDESC_CD_0_ENDI |
#endif
- CTXDESC_CD_0_R | CTXDESC_CD_0_A | CTXDESC_CD_0_ASET |
+ CTXDESC_CD_0_R | CTXDESC_CD_0_A |
+ (cd->mm ? 0 : CTXDESC_CD_0_ASET) |
CTXDESC_CD_0_AA64 |
FIELD_PREP(CTXDESC_CD_0_ASID, cd->asid) |
CTXDESC_CD_0_V;
@@ -1108,12 +1110,20 @@ static void arm_smmu_free_cd_tables(struct arm_smmu_domain *smmu_domain)
cdcfg->cdtab = NULL;
}

-static void arm_smmu_free_asid(struct arm_smmu_ctx_desc *cd)
+bool arm_smmu_free_asid(struct arm_smmu_ctx_desc *cd)
{
+ bool free;
+ struct arm_smmu_ctx_desc *old_cd;
+
if (!cd->asid)
- return;
+ return false;

- xa_erase(&asid_xa, cd->asid);
+ free = refcount_dec_and_test(&cd->refs);
+ if (free) {
+ old_cd = xa_erase(&arm_smmu_asid_xa, cd->asid);
+ WARN_ON(old_cd != cd);
+ }
+ return free;
}

/* Stream table manipulation functions */
@@ -1801,9 +1811,12 @@ static void arm_smmu_domain_free(struct iommu_domain *domain)
if (smmu_domain->stage == ARM_SMMU_DOMAIN_S1) {
struct arm_smmu_s1_cfg *cfg = &smmu_domain->s1_cfg;

+ /* Prevent SVA from touching the CD while we're freeing it */
+ mutex_lock(&arm_smmu_asid_lock);
if (cfg->cdcfg.cdtab)
arm_smmu_free_cd_tables(smmu_domain);
arm_smmu_free_asid(&cfg->cd);
+ mutex_unlock(&arm_smmu_asid_lock);
} else {
struct arm_smmu_s2_cfg *cfg = &smmu_domain->s2_cfg;
if (cfg->vmid)
@@ -1823,10 +1836,14 @@ static int arm_smmu_domain_finalise_s1(struct arm_smmu_domain *smmu_domain,
struct arm_smmu_s1_cfg *cfg = &smmu_domain->s1_cfg;
typeof(&pgtbl_cfg->arm_lpae_s1_cfg.tcr) tcr = &pgtbl_cfg->arm_lpae_s1_cfg.tcr;

- ret = xa_alloc(&asid_xa, &asid, &cfg->cd,
+ refcount_set(&cfg->cd.refs, 1);
+
+ /* Prevent SVA from modifying the ASID until it is written to the CD */
+ mutex_lock(&arm_smmu_asid_lock);
+ ret = xa_alloc(&arm_smmu_asid_xa, &asid, &cfg->cd,
XA_LIMIT(1, (1 << smmu->asid_bits) - 1), GFP_KERNEL);
if (ret)
- return ret;
+ goto out_unlock;

cfg->s1cdmax = master->ssid_bits;

@@ -1854,12 +1871,15 @@ static int arm_smmu_domain_finalise_s1(struct arm_smmu_domain *smmu_domain,
if (ret)
goto out_free_cd_tables;

+ mutex_unlock(&arm_smmu_asid_lock);
return 0;

out_free_cd_tables:
arm_smmu_free_cd_tables(smmu_domain);
out_free_asid:
arm_smmu_free_asid(&cfg->cd);
+out_unlock:
+ mutex_unlock(&arm_smmu_asid_lock);
return ret;
}