iommu/arm-smmu-v3: Implement iommu_sva_bind/unbind()

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>
Link: https://lore.kernel.org/r/20201106155048.997886-4-jean-philippe@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>

1 files changed, 24 insertions, 8 deletions

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 e634bbe60573..034ed126e5c8 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -76,6 +76,12 @@ struct arm_smmu_option_prop {
 DEFINE_XARRAY_ALLOC1(arm_smmu_asid_xa);
 DEFINE_MUTEX(arm_smmu_asid_lock);
 
+/*
+ * Special value used by SVA when a process dies, to quiesce a CD without
+ * disabling it.
+ */
+struct arm_smmu_ctx_desc quiet_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"},
@@ -91,11 +97,6 @@ static inline void __iomem *arm_smmu_page1_fixup(unsigned long offset,
 	return smmu->base + offset;
 }
 
-static struct arm_smmu_domain *to_smmu_domain(struct iommu_domain *dom)
-{
-	return container_of(dom, struct arm_smmu_domain, domain);
-}
-
 static void parse_driver_options(struct arm_smmu_device *smmu)
 {
 	int i = 0;
@@ -983,7 +984,9 @@ int arm_smmu_write_ctx_desc(struct arm_smmu_domain *smmu_domain, int ssid,
 	 * (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;
@@ -1000,8 +1003,10 @@ int arm_smmu_write_ctx_desc(struct arm_smmu_domain *smmu_domain, int ssid,
 	val = le64_to_cpu(cdptr[0]);
 	cd_live = !!(val & CTXDESC_CD_0_V);
 
-	if (!cd) { /* (4) */
+	if (!cd) { /* (5) */
 		val = 0;
+	} else if (cd == &quiet_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);
@@ -1794,6 +1799,7 @@ 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;
 }
@@ -2589,6 +2595,9 @@ 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 */
 };
 
@@ -3611,6 +3620,12 @@ 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)
+{
+	arm_smmu_sva_notifier_synchronize();
+	platform_driver_unregister(drv);
+}
+
 static struct platform_driver arm_smmu_driver = {
 	.driver	= {
 		.name			= "arm-smmu-v3",
@@ -3621,7 +3636,8 @@ 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>");