[PATCH v2 23/40] iommu/arm-smmu-v3: Share process page tables

Jean-Philippe Brucker
2018-05-11T19:06:24Z

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.

Replace the ASID IDA with an IDR, allowing to keep information about each
context. Initialize shared contexts with info obtained from the mm.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker-5wv7dgnIgG8@public.gmane.org>
---
drivers/iommu/arm-smmu-v3-context.c | 182 ++++++++++++++++++++++++++--
1 file changed, 172 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3-context.c b/drivers/iommu/arm-smmu-v3-context.c
index d68da99aa472..352cba3c1a62 100644
--- a/drivers/iommu/arm-smmu-v3-context.c
+++ b/drivers/iommu/arm-smmu-v3-context.c
@@ -10,8 +10,10 @@
#include <linux/dma-mapping.h>
#include <linux/idr.h>
#include <linux/kernel.h>
+#include <linux/mmu_context.h>
#include <linux/slab.h>

+#include "io-pgtable-arm.h"
#include "iommu-pasid-table.h"

/*
@@ -69,6 +71,9 @@ struct arm_smmu_cd {
u64 ttbr;
u64 tcr;
u64 mair;
+
+ refcount_t refs;
+ struct mm_struct *mm;
};

#define pasid_entry_to_cd(entry) \
@@ -100,7 +105,8 @@ struct arm_smmu_cd_tables {
#define pasid_ops_to_tables(ops) \
pasid_to_cd_tables(iommu_pasid_table_ops_to_table(ops))

-static DEFINE_IDA(asid_ida);
+static DEFINE_SPINLOCK(asid_lock);
+static DEFINE_IDR(asid_idr);

static int arm_smmu_alloc_cd_leaf_table(struct device *dev,
struct arm_smmu_cd_table *desc,
@@ -239,7 +245,8 @@ static int arm_smmu_write_ctx_desc(struct arm_smmu_cd_tables *tbl, int ssid,
#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->entry.tag) |
CTXDESC_CD_0_V;
@@ -255,18 +262,161 @@ static int arm_smmu_write_ctx_desc(struct arm_smmu_cd_tables *tbl, int ssid,
return 0;
}

+static bool arm_smmu_free_asid(struct arm_smmu_cd *cd)
+{
+ bool free;
+ struct arm_smmu_cd *old_cd;
+
+ spin_lock(&asid_lock);
+ free = refcount_dec_and_test(&cd->refs);
+ if (free) {
+ old_cd = idr_remove(&asid_idr, (u16)cd->entry.tag);
+ WARN_ON(old_cd != cd);
+ }
+ spin_unlock(&asid_lock);
+
+ return free;
+}
+
static void arm_smmu_free_cd(struct iommu_pasid_entry *entry)
{
struct arm_smmu_cd *cd = pasid_entry_to_cd(entry);

- ida_simple_remove(&asid_ida, (u16)entry->tag);
+ if (!arm_smmu_free_asid(cd))
+ return;
+
+ if (cd->mm) {
+ /* Unpin ASID */
+ mm_context_put(cd->mm);
+ }
+
kfree(cd);
}

+static struct arm_smmu_cd *arm_smmu_alloc_cd(struct arm_smmu_cd_tables *tbl)
+{
+ struct arm_smmu_cd *cd;
+
+ cd = kzalloc(sizeof(*cd), GFP_KERNEL);
+ if (!cd)
+ return NULL;
+
+ cd->entry.release = arm_smmu_free_cd;
+ refcount_set(&cd->refs, 1);
+
+ return cd;
+}
+
+static struct arm_smmu_cd *arm_smmu_share_asid(u16 asid)
+{
+ struct arm_smmu_cd *cd;
+
+ cd = idr_find(&asid_idr, asid);
+ if (!cd)
+ return NULL;
+
+ if (cd->mm) {
+ /*
+ * It's pretty common to find a stale CD when doing unbind-bind,
+ * given that the release happens after a RCU grace period.
+ * Simply reuse it.
+ */
+ refcount_inc(&cd->refs);
+ return cd;
+ }
+
+ /*
+ * Ouch, ASID is already in use for a private cd.
+ * TODO: seize it, for the common good.
+ */
+ return ERR_PTR(-EEXIST);
+}
+
static struct iommu_pasid_entry *
arm_smmu_alloc_shared_cd(struct iommu_pasid_table_ops *ops, struct mm_struct *mm)
{
- return ERR_PTR(-ENODEV);
+ u16 asid;
+ u64 tcr, par, reg;
+ int ret = -ENOMEM;
+ struct arm_smmu_cd *cd;
+ struct arm_smmu_cd *old_cd = NULL;
+ struct arm_smmu_cd_tables *tbl = pasid_ops_to_tables(ops);
+
+ asid = mm_context_get(mm);
+ if (!asid)
+ return ERR_PTR(-ESRCH);
+
+ cd = arm_smmu_alloc_cd(tbl);
+ if (!cd)
+ goto err_put_context;
+
+ idr_preload(GFP_KERNEL);
+ spin_lock(&asid_lock);
+ old_cd = arm_smmu_share_asid(asid);
+ if (!old_cd)
+ ret = idr_alloc(&asid_idr, cd, asid, asid + 1, GFP_ATOMIC);
+ spin_unlock(&asid_lock);
+ idr_preload_end();
+
+ if (!IS_ERR_OR_NULL(old_cd)) {
+ if (WARN_ON(old_cd->mm != mm)) {
+ ret = -EINVAL;
+ goto err_free_cd;
+ }
+ kfree(cd);
+ mm_context_put(mm);
+ return &old_cd->entry;
+ } else if (old_cd) {
+ ret = PTR_ERR(old_cd);
+ goto err_free_cd;
+ }
+
+ tcr = TCR_T0SZ(VA_BITS) | TCR_IRGN0_WBWA | TCR_ORGN0_WBWA |
+ TCR_SH0_INNER | ARM_LPAE_TCR_EPD1;
+
+ switch (PAGE_SIZE) {
+ case SZ_4K:
+ tcr |= TCR_TG0_4K;
+ break;
+ case SZ_16K:
+ tcr |= TCR_TG0_16K;
+ break;
+ case SZ_64K:
+ tcr |= TCR_TG0_64K;
+ break;
+ default:
+ WARN_ON(1);
+ ret = -EINVAL;
+ goto err_free_asid;
+ }
+
+ reg = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
+ par = cpuid_feature_extract_unsigned_field(reg, ID_AA64MMFR0_PARANGE_SHIFT);
+ tcr |= par << ARM_LPAE_TCR_IPS_SHIFT;
+
+ 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->mm = mm;
+ cd->entry.tag = asid;
+
+ return &cd->entry;
+
+err_free_asid:
+ arm_smmu_free_asid(cd);
+
+err_free_cd:
+ kfree(cd);
+
+err_put_context:
+ mm_context_put(mm);
+
+ return ERR_PTR(ret);
}

static struct iommu_pasid_entry *
@@ -280,20 +430,23 @@ arm_smmu_alloc_priv_cd(struct iommu_pasid_table_ops *ops,
struct arm_smmu_cd_tables *tbl = pasid_ops_to_tables(ops);
struct arm_smmu_context_cfg *ctx_cfg = &tbl->pasid.cfg.arm_smmu;

- cd = kzalloc(sizeof(*cd), GFP_KERNEL);
+ cd = arm_smmu_alloc_cd(tbl);
if (!cd)
return ERR_PTR(-ENOMEM);

- asid = ida_simple_get(&asid_ida, 0, 1 << ctx_cfg->asid_bits,
- GFP_KERNEL);
+ idr_preload(GFP_KERNEL);
+ spin_lock(&asid_lock);
+ asid = idr_alloc_cyclic(&asid_idr, cd, 0, 1 << ctx_cfg->asid_bits,
+ GFP_ATOMIC);
+ cd->entry.tag = asid;
+ spin_unlock(&asid_lock);
+ idr_preload_end();
+
if (asid < 0) {
kfree(cd);
return ERR_PTR(asid);
}

- cd->entry.tag = asid;
- cd->entry.release = arm_smmu_free_cd;
-
switch (fmt) {
case ARM_64_LPAE_S1:
cd->ttbr = cfg->arm_lpae_s1_cfg.ttbr[0];
@@ -330,11 +483,20 @@ static void arm_smmu_clear_cd(struct iommu_pasid_table_ops *ops, int pasid,
struct iommu_pasid_entry *entry)
{
struct arm_smmu_cd_tables *tbl = pasid_ops_to_tables(ops);
+ struct arm_smmu_cd *cd = pasid_entry_to_cd(entry);

if (WARN_ON(pasid > (1 << tbl->pasid.cfg.order)))
return;

arm_smmu_write_ctx_desc(tbl, pasid, NULL);
+
+ /*
+ * The ASID allocator won't broadcast the final TLB invalidations for
+ * this ASID, so we need to do it manually. For private contexts,
+ * freeing io-pgtable ops performs the invalidation.
+ */
+ if (cd->mm)
+ iommu_pasid_flush_tlbs(&tbl->pasid, pasid, entry);
}

static struct iommu_pasid_table *
--
2.17.0