[PATCH v7 16/24] iommu/arm-smmu-v3: Implement iommu_sva_bind/unbind()

Jean-Philippe Brucker
2020-05-19T18:08:01Z

The sva_bind() function allows devices to access process address spaces
using a PASID (aka SSID).

(1) bind() allocates or gets an existing MMU notifier tied to the
(domain, mm) pair. Each mm gets one PASID.

(2) Any change to the address space calls invalidate_range() which sends
ATC invalidations (in a subsequent patch).

(3) When the process address space dies, the release() notifier disables
the CD to allow reclaiming the page tables. Since release() has to
be light we do not instruct device drivers to stop DMA here, we just
ignore incoming page faults from this point onwards.

To avoid any event 0x0a print (C_BAD_CD) we disable translation
without clearing CD.V. PCIe Translation Requests and Page Requests
are silently denied. Don't clear the R bit because the S bit can't
be cleared when STALL_MODEL==0b10 (forced), and clearing R without
clearing S is useless. Faulting transactions will stall and will be
aborted by the IOPF handler.

(4) After stopping DMA, the device driver releases the bond by calling
unbind(). We release the MMU notifier, free the PASID and the bond.

Three structures keep track of bonds:
* arm_smmu_bond: one per {device, mm} pair, the handle returned to the
device driver for a bind() request.
* arm_smmu_mmu_notifier: one per {domain, mm} pair, deals with ATS/TLB
invalidations and clearing the context descriptor on mm exit.
* arm_smmu_ctx_desc: one per mm, holds the pinned ASID and pgd.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
v6->v7: Keep track of {domains, mm} pairs. Move
mmu_notifier_synchronize() to module_exit().
---
drivers/iommu/Kconfig | 2 +
drivers/iommu/arm-smmu-v3.c | 272 +++++++++++++++++++++++++++++++++++-
2 files changed, 269 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 15e9dc4e503c..00b517f449ab 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -432,8 +432,10 @@ config ARM_SMMU_V3
tristate "ARM Ltd. System MMU Version 3 (SMMUv3) Support"
depends on ARM64
select IOMMU_API
+ select IOMMU_SVA
select IOMMU_IO_PGTABLE_LPAE
select GENERIC_MSI_IRQ_DOMAIN
+ select MMU_NOTIFIER
help
Support for implementations of the ARM System MMU architecture
version 3 providing translation support to a PCIe root complex.
diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index b016b61cee23..00a9342eed99 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -24,6 +24,7 @@
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/mmu_context.h>
+#include <linux/mmu_notifier.h>
#include <linux/msi.h>
#include <linux/of.h>
#include <linux/of_address.h>
@@ -36,6 +37,7 @@
#include <linux/amba/bus.h>

#include "io-pgtable-arm.h"
+#include "iommu-sva.h"

/* MMIO registers */
#define ARM_SMMU_IDR0 0x0
@@ -734,8 +736,32 @@ struct arm_smmu_domain {

struct list_head devices;
spinlock_t devices_lock;
+
+ struct list_head mmu_notifiers;
+};
+
+struct arm_smmu_mmu_notifier {
+ struct mmu_notifier mn;
+ struct arm_smmu_ctx_desc *cd;
+ bool cleared;
+ refcount_t refs;
+ struct list_head list;
+ struct arm_smmu_domain *domain;
};

+#define mn_to_smmu(mn) container_of(mn, struct arm_smmu_mmu_notifier, mn)
+
+struct arm_smmu_bond {
+ struct iommu_sva sva;
+ struct mm_struct *mm;
+ struct arm_smmu_mmu_notifier *smmu_mn;
+ struct list_head list;
+ refcount_t refs;
+};
+
+#define sva_to_bond(handle) \
+ container_of(handle, struct arm_smmu_bond, sva)
+
struct arm_smmu_option_prop {
u32 opt;
const char *prop;
@@ -745,6 +771,13 @@ static DEFINE_XARRAY_ALLOC1(asid_xa);
static DEFINE_MUTEX(asid_lock);
static DEFINE_MUTEX(sva_lock);

+/*
+ * When a process dies, DMA is still running but we need to clear the pgd. If we
+ * simply cleared the valid bit from the context descriptor, we'd get event 0x0a
+ * which are not recoverable.
+ */
+static struct arm_smmu_ctx_desc invalid_cd = { 0 };
+
static struct arm_smmu_option_prop arm_smmu_options[] = {
{ ARM_SMMU_OPT_SKIP_PREFETCH, "hisilicon,broken-prefetch-cmd" },
{ ARM_SMMU_OPT_PAGE0_REGS_ONLY, "cavium,cn9900-broken-page1-regspace"},
@@ -1654,7 +1687,9 @@ static int arm_smmu_write_ctx_desc(struct arm_smmu_domain *smmu_domain,
* (2) Install a secondary CD, for SID+SSID traffic.
* (3) Update ASID of a CD. Atomically write the first 64 bits of the
* CD, then invalidate the old entry and mappings.
- * (4) Remove a secondary CD.
+ * (4) Quiesce the context without clearing the valid bit. Disable
+ * translation, and ignore any translation fault.
+ * (5) Remove a secondary CD.
*/
u64 val;
bool cd_live;
@@ -1671,8 +1706,10 @@ static int arm_smmu_write_ctx_desc(struct arm_smmu_domain *smmu_domain,
val = le64_to_cpu(cdptr[0]);
cd_live = !!(val & CTXDESC_CD_0_V);

- if (!cd) { /* (4) */
+ if (!cd) { /* (5) */
val = 0;
+ } else if (cd == &invalid_cd) { /* (4) */
+ val |= CTXDESC_CD_0_TCR_EPD0;
} else if (cd_live) { /* (3) */
val &= ~CTXDESC_CD_0_ASID;
val |= FIELD_PREP(CTXDESC_CD_0_ASID, cd->asid);
@@ -1872,7 +1909,6 @@ static struct arm_smmu_ctx_desc *arm_smmu_share_asid(u16 asid)
return NULL;
}

-__maybe_unused
static struct arm_smmu_ctx_desc *arm_smmu_alloc_shared_cd(struct mm_struct *mm)
{
u16 asid;
@@ -1969,7 +2005,6 @@ static struct arm_smmu_ctx_desc *arm_smmu_alloc_shared_cd(struct mm_struct *mm)
return ERR_PTR(ret);
}

-__maybe_unused
static void arm_smmu_free_shared_cd(struct arm_smmu_ctx_desc *cd)
{
lockdep_assert_held(&sva_lock);
@@ -2606,6 +2641,8 @@ static bool arm_smmu_capable(enum iommu_cap cap)
}
}

+static struct mmu_notifier_ops arm_smmu_mmu_notifier_ops;
+
static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
{
struct arm_smmu_domain *smmu_domain;
@@ -2633,6 +2670,7 @@ static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
mutex_init(&smmu_domain->init_mutex);
INIT_LIST_HEAD(&smmu_domain->devices);
spin_lock_init(&smmu_domain->devices_lock);
+ INIT_LIST_HEAD(&smmu_domain->mmu_notifiers);

return &smmu_domain->domain;
}
@@ -3127,6 +3165,216 @@ arm_smmu_iova_to_phys(struct iommu_domain *domain, dma_addr_t iova)
return ops->iova_to_phys(ops, iova);
}

+static void arm_smmu_mm_invalidate_range(struct mmu_notifier *mn,
+ struct mm_struct *mm,
+ unsigned long start, unsigned long end)
+{
+ /* TODO: invalidate ATS */
+}
+
+static void arm_smmu_mm_release(struct mmu_notifier *mn, struct mm_struct *mm)
+{
+ struct arm_smmu_mmu_notifier *smmu_mn = mn_to_smmu(mn);
+ struct arm_smmu_domain *smmu_domain = smmu_mn->domain;
+
+ mutex_lock(&sva_lock);
+ if (smmu_mn->cleared) {
+ mutex_unlock(&sva_lock);
+ return;
+ }
+
+ /*
+ * DMA may still be running. Keep the cd valid to avoid C_BAD_CD events,
+ * but disable translation.
+ */
+ arm_smmu_write_ctx_desc(smmu_domain, mm->pasid, &invalid_cd);
+
+ arm_smmu_tlb_inv_asid(smmu_domain->smmu, smmu_mn->cd->asid);
+ /* TODO: invalidate ATS */
+
+ smmu_mn->cleared = true;
+ mutex_unlock(&sva_lock);
+}
+
+static void arm_smmu_mmu_notifier_free(struct mmu_notifier *mn)
+{
+ kfree(mn_to_smmu(mn));
+}
+
+static struct mmu_notifier_ops arm_smmu_mmu_notifier_ops = {
+ .invalidate_range = arm_smmu_mm_invalidate_range,
+ .release = arm_smmu_mm_release,
+ .free_notifier = arm_smmu_mmu_notifier_free,
+};
+
+/* Allocate or get existing MMU notifier for this {domain, mm} pair */
+static struct arm_smmu_mmu_notifier *
+arm_smmu_mmu_notifier_get(struct arm_smmu_domain *smmu_domain,
+ struct mm_struct *mm)
+{
+ int ret;
+ struct arm_smmu_ctx_desc *cd;
+ struct arm_smmu_mmu_notifier *smmu_mn;
+
+ lockdep_assert_held(&sva_lock);
+
+ list_for_each_entry(smmu_mn, &smmu_domain->mmu_notifiers, list) {
+ if (smmu_mn->mn.mm == mm) {
+ refcount_inc(&smmu_mn->refs);
+ return smmu_mn;
+ }
+ }
+
+ cd = arm_smmu_alloc_shared_cd(mm);
+ if (IS_ERR(cd))
+ return ERR_CAST(cd);
+
+ smmu_mn = kzalloc(sizeof(*smmu_mn), GFP_KERNEL);
+ if (!smmu_mn) {
+ ret = -ENOMEM;
+ goto err_free_cd;
+ }
+
+ refcount_set(&smmu_mn->refs, 1);
+ smmu_mn->cd = cd;
+ smmu_mn->domain = smmu_domain;
+ smmu_mn->mn.ops = &arm_smmu_mmu_notifier_ops;
+
+ ret = mmu_notifier_register(&smmu_mn->mn, mm);
+ if (ret) {
+ kfree(smmu_mn);
+ goto err_free_cd;
+ }
+
+ ret = arm_smmu_write_ctx_desc(smmu_domain, mm->pasid, cd);
+ if (ret)
+ goto err_put_notifier;
+
+ list_add(&smmu_mn->list, &smmu_domain->mmu_notifiers);
+ return smmu_mn;
+
+err_put_notifier:
+ /* Frees smmu_mn */
+ mmu_notifier_put(&smmu_mn->mn);
+err_free_cd:
+ arm_smmu_free_shared_cd(cd);
+ return ERR_PTR(ret);
+}
+
+static void arm_smmu_mmu_notifier_put(struct arm_smmu_mmu_notifier *smmu_mn)
+{
+ struct mm_struct *mm = smmu_mn->mn.mm;
+ struct arm_smmu_ctx_desc *cd = smmu_mn->cd;
+ struct arm_smmu_domain *smmu_domain = smmu_mn->domain;
+
+ lockdep_assert_held(&sva_lock);
+
+ if (!refcount_dec_and_test(&smmu_mn->refs))
+ return;
+
+ list_del(&smmu_mn->list);
+ arm_smmu_write_ctx_desc(smmu_domain, mm->pasid, NULL);
+
+ /*
+ * If we went through clear(), we've already invalidated, and no
+ * new TLB entry can have been formed.
+ */
+ if (!smmu_mn->cleared) {
+ arm_smmu_tlb_inv_asid(smmu_domain->smmu, cd->asid);
+ /* TODO: invalidate ATS */
+ }
+
+ /* Frees smmu_mn */
+ mmu_notifier_put(&smmu_mn->mn);
+ arm_smmu_free_shared_cd(cd);
+}
+
+static struct iommu_sva *
+__arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm)
+{
+ int ret;
+ struct arm_smmu_bond *bond;
+ struct arm_smmu_master *master = dev_iommu_priv_get(dev);
+ struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
+ struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
+
+ lockdep_assert_held(&sva_lock);
+
+ if (!master || !master->sva_enabled)
+ return ERR_PTR(-ENODEV);
+
+ /* If bind() was already called for this {dev, mm} pair, reuse it. */
+ list_for_each_entry(bond, &master->bonds, list) {
+ if (bond->mm == mm) {
+ refcount_inc(&bond->refs);
+ return &bond->sva;
+ }
+ }
+
+ bond = kzalloc(sizeof(*bond), GFP_KERNEL);
+ if (!bond)
+ return ERR_PTR(-ENOMEM);
+
+ /* Allocate a PASID for this mm if necessary */
+ ret = iommu_sva_alloc_pasid(mm, 1, (1U << master->ssid_bits) - 1);
+ if (ret)
+ goto err_free_bond;
+
+ bond->mm = mm;
+ bond->sva.dev = dev;
+ refcount_set(&bond->refs, 1);
+
+ bond->smmu_mn = arm_smmu_mmu_notifier_get(smmu_domain, mm);
+ if (IS_ERR(bond->smmu_mn))
+ goto err_free_pasid;
+
+ list_add(&bond->list, &master->bonds);
+ return &bond->sva;
+
+err_free_pasid:
+ iommu_sva_free_pasid(mm);
+err_free_bond:
+ kfree(bond);
+ return ERR_PTR(ret);
+}
+
+static struct iommu_sva *
+arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm, void *drvdata)
+{
+ struct iommu_sva *handle;
+ struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
+ struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
+
+ if (smmu_domain->stage != ARM_SMMU_DOMAIN_S1)
+ return ERR_PTR(-EINVAL);
+
+ mutex_lock(&sva_lock);
+ handle = __arm_smmu_sva_bind(dev, mm);
+ mutex_unlock(&sva_lock);
+ return handle;
+}
+
+static void arm_smmu_sva_unbind(struct iommu_sva *handle)
+{
+ struct arm_smmu_bond *bond = sva_to_bond(handle);
+
+ mutex_lock(&sva_lock);
+ if (refcount_dec_and_test(&bond->refs)) {
+ list_del(&bond->list);
+ arm_smmu_mmu_notifier_put(bond->smmu_mn);
+ iommu_sva_free_pasid(bond->mm);
+ kfree(bond);
+ }
+ mutex_unlock(&sva_lock);
+}
+
+static int arm_smmu_sva_get_pasid(struct iommu_sva *handle)
+{
+ struct arm_smmu_bond *bond = sva_to_bond(handle);
+
+ return bond->mm->pasid;
+}
+
static struct platform_driver arm_smmu_driver;

static
@@ -3491,6 +3739,9 @@ static struct iommu_ops arm_smmu_ops = {
.dev_feat_enabled = arm_smmu_dev_feature_enabled,
.dev_enable_feat = arm_smmu_dev_enable_feature,
.dev_disable_feat = arm_smmu_dev_disable_feature,
+ .sva_bind = arm_smmu_sva_bind,
+ .sva_unbind = arm_smmu_sva_unbind,
+ .sva_get_pasid = arm_smmu_sva_get_pasid,
.pgsize_bitmap = -1UL, /* Restricted during device attach */
};

@@ -4598,6 +4849,16 @@ static const struct of_device_id arm_smmu_of_match[] = {
};
MODULE_DEVICE_TABLE(of, arm_smmu_of_match);

+static void arm_smmu_driver_unregister(struct platform_driver *drv)
+{
+ /*
+ * Wait for all notifiers free() RCU callbacks, since they are still
+ * using the arm_smmu_mmu_notifier_ops.
+ */
+ mmu_notifier_synchronize();
+ platform_driver_unregister(drv);
+}
+
static struct platform_driver arm_smmu_driver = {
.driver = {
.name = "arm-smmu-v3",
@@ -4608,7 +4869,8 @@ static struct platform_driver arm_smmu_driver = {
.remove = arm_smmu_device_remove,
.shutdown = arm_smmu_device_shutdown,
};
-module_platform_driver(arm_smmu_driver);
+module_driver(arm_smmu_driver, platform_driver_register,
+ arm_smmu_driver_unregister);

MODULE_DESCRIPTION("IOMMU API for ARM architected SMMUv3 implementations");
MODULE_AUTHOR("Will Deacon <will@kernel.org>");