ocxl: Add mmu notifier

Add invalidate_range mmu notifier, when required (ATSD access of MMIO
registers is available), to initiate TLB invalidation commands.
For the time being, the ATSD0 set of registers is used by default.

The pasid and bdf values have to be configured in the Process Element
Entry.
The PEE must be set up to match the BDF/PASID of the AFU.

Signed-off-by: Christophe Lombard <clombard@linux.vnet.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201125155013.39955-5-clombard@linux.vnet.ibm.com

drivers/misc/ocxl/link.c

@@ -2,8 +2,10 @@
 // Copyright 2017 IBM Corp.
 #include <linux/sched/mm.h>
 #include <linux/mutex.h>
+#include <linux/mm.h>
 #include <linux/mm_types.h>
 #include <linux/mmu_context.h>
+#include <linux/mmu_notifier.h>
 #include <asm/copro.h>
 #include <asm/pnv-ocxl.h>
 #include <asm/xive.h>
@@ -33,6 +35,7 @@
 
 #define SPA_PE_VALID		0x80000000
 
+struct ocxl_link;
 
 struct pe_data {
 	struct mm_struct *mm;
@@ -41,6 +44,8 @@ struct pe_data {
 	/* opaque pointer to be passed to the above callback */
 	void *xsl_err_data;
 	struct rcu_head rcu;
+	struct ocxl_link *link;
+	struct mmu_notifier mmu_notifier;
 };
 
 struct spa {
@@ -83,6 +88,8 @@ struct ocxl_link {
 	int domain;
 	int bus;
 	int dev;
+	void __iomem *arva;     /* ATSD register virtual address */
+	spinlock_t atsd_lock;   /* to serialize shootdowns */
 	atomic_t irq_available;
 	struct spa *spa;
 	void *platform_data;
@@ -388,6 +395,7 @@ static int alloc_link(struct pci_dev *dev, int PE_mask, struct ocxl_link **out_l
 	link->bus = dev->bus->number;
 	link->dev = PCI_SLOT(dev->devfn);
 	atomic_set(&link->irq_available, MAX_IRQ_PER_LINK);
+	spin_lock_init(&link->atsd_lock);
 
 	rc = alloc_spa(dev, link);
 	if (rc)
@@ -403,6 +411,13 @@ static int alloc_link(struct pci_dev *dev, int PE_mask, struct ocxl_link **out_l
 	if (rc)
 		goto err_xsl_irq;
 
+	/* if link->arva is not defeined, MMIO registers are not used to
+	 * generate TLB invalidate. PowerBus snooping is enabled.
+	 * Otherwise, PowerBus snooping is disabled. TLB Invalidates are
+	 * initiated using MMIO registers.
+	 */
+	pnv_ocxl_map_lpar(dev, mfspr(SPRN_LPID), 0, &link->arva);
+
 	*out_link = link;
 	return 0;
 
@@ -454,6 +469,11 @@ static void release_xsl(struct kref *ref)
 {
 	struct ocxl_link *link = container_of(ref, struct ocxl_link, ref);
 
+	if (link->arva) {
+		pnv_ocxl_unmap_lpar(link->arva);
+		link->arva = NULL;
+	}
+
 	list_del(&link->list);
 	/* call platform code before releasing data */
 	pnv_ocxl_spa_release(link->platform_data);
@@ -470,6 +490,26 @@ void ocxl_link_release(struct pci_dev *dev, void *link_handle)
 }
 EXPORT_SYMBOL_GPL(ocxl_link_release);
 
+static void invalidate_range(struct mmu_notifier *mn,
+			     struct mm_struct *mm,
+			     unsigned long start, unsigned long end)
+{
+	struct pe_data *pe_data = container_of(mn, struct pe_data, mmu_notifier);
+	struct ocxl_link *link = pe_data->link;
+	unsigned long addr, pid, page_size = PAGE_SIZE;
+
+	pid = mm->context.id;
+
+	spin_lock(&link->atsd_lock);
+	for (addr = start; addr < end; addr += page_size)
+		pnv_ocxl_tlb_invalidate(link->arva, pid, addr, page_size);
+	spin_unlock(&link->atsd_lock);
+}
+
+static const struct mmu_notifier_ops ocxl_mmu_notifier_ops = {
+	.invalidate_range = invalidate_range,
+};
+
 static u64 calculate_cfg_state(bool kernel)
 {
 	u64 state;
@@ -526,6 +566,8 @@ int ocxl_link_add_pe(void *link_handle, int pasid, u32 pidr, u32 tidr,
 	pe_data->mm = mm;
 	pe_data->xsl_err_cb = xsl_err_cb;
 	pe_data->xsl_err_data = xsl_err_data;
+	pe_data->link = link;
+	pe_data->mmu_notifier.ops = &ocxl_mmu_notifier_ops;
 
 	memset(pe, 0, sizeof(struct ocxl_process_element));
 	pe->config_state = cpu_to_be64(calculate_cfg_state(pidr == 0));
@@ -542,8 +584,16 @@ int ocxl_link_add_pe(void *link_handle, int pasid, u32 pidr, u32 tidr,
 	 * by the nest MMU. If we have a kernel context, TLBIs are
 	 * already global.
 	 */
-	if (mm)
+	if (mm) {
 		mm_context_add_copro(mm);
+		if (link->arva) {
+			/* Use MMIO registers for the TLB Invalidate
+			 * operations.
+			 */
+			mmu_notifier_register(&pe_data->mmu_notifier, mm);
+		}
+	}
+
 	/*
 	 * Barrier is to make sure PE is visible in the SPA before it
 	 * is used by the device. It also helps with the global TLBI
@@ -674,6 +724,16 @@ int ocxl_link_remove_pe(void *link_handle, int pasid)
 		WARN(1, "Couldn't find pe data when removing PE\n");
 	} else {
 		if (pe_data->mm) {
+			if (link->arva) {
+				mmu_notifier_unregister(&pe_data->mmu_notifier,
+							pe_data->mm);
+				spin_lock(&link->atsd_lock);
+				pnv_ocxl_tlb_invalidate(link->arva,
+							pe_data->mm->context.id,
+							0ull,
+							PAGE_SIZE);
+				spin_unlock(&link->atsd_lock);
+			}
 			mm_context_remove_copro(pe_data->mm);
 			mmdrop(pe_data->mm);
 		}