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iommu/arm-smmu-v3: Share process page tables

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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>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20200918101852.582559-9-jean-philippe@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Jean-Philippe Brucker 2020-09-18 12:18:48 +02:00 committed by Will Deacon
parent e881e7839f
commit 3f1ce8e85e
5 changed files with 173 additions and 9 deletions
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10
drivers/iommu/Kconfig
View file

@ -308,6 +308,16 @@ 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

5
drivers/iommu/arm/arm-smmu-v3/Makefile
View file

@ -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)

123
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c Normal file
View file

@ -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 - vabits_actual) |
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);
}
}

36
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
View file

@ -73,7 +73,8 @@ 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" },
@ -1013,7 +1014,8 @@ 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;
@ -1117,12 +1119,20 @@ 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)
{
if (!cd->asid)
return;
bool free;
struct arm_smmu_ctx_desc *old_cd;
xa_erase(&asid_xa, cd->asid);
if (!cd->asid)
return false;
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 */
@ -1810,9 +1820,12 @@ 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)
@ -1832,10 +1845,14 @@ 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;
@ -1863,12 +1880,15 @@ 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;
}

8
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
View file

@ -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 {
@ -673,4 +676,9 @@ 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 */