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From: Elliot Berman <quic_eberman@quicinc.com>
Date: Fri, 15 Dec 2023 16:20:55 -0800
Subject: [PATCH RFC v15 14/30] virt: gunyah: Add IO handlers
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Message-ID: <20231215-gunyah-v15-14-192a5d872a30@quicinc.com>
References: <20231215-gunyah-v15-0-192a5d872a30@quicinc.com>
In-Reply-To: <20231215-gunyah-v15-0-192a5d872a30@quicinc.com>
To: Alex Elder <elder@linaro.org>,
        Srinivas Kandagatla
	<srinivas.kandagatla@linaro.org>,
        Murali Nalajal <quic_mnalajal@quicinc.com>,
        Trilok Soni <quic_tsoni@quicinc.com>,
        Srivatsa Vaddagiri
	<quic_svaddagi@quicinc.com>,
        Carl van Schaik <quic_cvanscha@quicinc.com>,
        Philip Derrin <quic_pderrin@quicinc.com>,
        Prakruthi Deepak Heragu
	<quic_pheragu@quicinc.com>,
        Jonathan Corbet <corbet@lwn.net>, Rob Herring
	<robh+dt@kernel.org>,
        Krzysztof Kozlowski
	<krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Bjorn Andersson
	<andersson@kernel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        "Fuad
 Tabba" <tabba@google.com>,
        Sean Christopherson <seanjc@google.com>
CC: <linux-arm-msm@vger.kernel.org>, <linux-doc@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        Elliot Berman
	<quic_eberman@quicinc.com>

Add framework for VM functions to handle stage-2 write faults from Gunyah
guest virtual machines. IO handlers have a range of addresses which they
apply to. Optionally, they may apply to only when the value written
matches the IO handler's value.

Reviewed-by: Alex Elder <elder@linaro.org>
Co-developed-by: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
Signed-off-by: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
---
 drivers/virt/gunyah/vm_mgr.c  | 114 ++++++++++++++++++++++++++++++++++++++++++
 drivers/virt/gunyah/vm_mgr.h  |   5 ++
 include/linux/gunyah_vm_mgr.h |  29 +++++++++++
 3 files changed, 148 insertions(+)

diff --git a/drivers/virt/gunyah/vm_mgr.c b/drivers/virt/gunyah/vm_mgr.c
index fb22459b21c8..8feb9302d7d2 100644
--- a/drivers/virt/gunyah/vm_mgr.c
+++ b/drivers/virt/gunyah/vm_mgr.c
@@ -285,6 +285,118 @@ static void gunyah_vm_clean_resources(struct gunyah_vm *ghvm)
 	mutex_unlock(&ghvm->resources_lock);
 }
 
+static int _gunyah_vm_io_handler_compare(const struct rb_node *node,
+					 const struct rb_node *parent)
+{
+	struct gunyah_vm_io_handler *n =
+		container_of(node, struct gunyah_vm_io_handler, node);
+	struct gunyah_vm_io_handler *p =
+		container_of(parent, struct gunyah_vm_io_handler, node);
+
+	if (n->addr < p->addr)
+		return -1;
+	if (n->addr > p->addr)
+		return 1;
+	if ((n->len && !p->len) || (!n->len && p->len))
+		return 0;
+	if (n->len < p->len)
+		return -1;
+	if (n->len > p->len)
+		return 1;
+	/* one of the io handlers doesn't have datamatch and the other does.
+	 * For purposes of comparison, that makes them identical since the
+	 * one that doesn't have datamatch will cover the same handler that
+	 * does.
+	 */
+	if (n->datamatch != p->datamatch)
+		return 0;
+	if (n->data < p->data)
+		return -1;
+	if (n->data > p->data)
+		return 1;
+	return 0;
+}
+
+static int gunyah_vm_io_handler_compare(struct rb_node *node,
+					const struct rb_node *parent)
+{
+	return _gunyah_vm_io_handler_compare(node, parent);
+}
+
+static int gunyah_vm_io_handler_find(const void *key,
+				     const struct rb_node *node)
+{
+	const struct gunyah_vm_io_handler *k = key;
+
+	return _gunyah_vm_io_handler_compare(&k->node, node);
+}
+
+static struct gunyah_vm_io_handler *
+gunyah_vm_mgr_find_io_hdlr(struct gunyah_vm *ghvm, u64 addr, u64 len, u64 data)
+{
+	struct gunyah_vm_io_handler key = {
+		.addr = addr,
+		.len = len,
+		.datamatch = true,
+		.data = data,
+	};
+	struct rb_node *node;
+
+	node = rb_find(&key, &ghvm->mmio_handler_root,
+		       gunyah_vm_io_handler_find);
+	if (!node)
+		return NULL;
+
+	return container_of(node, struct gunyah_vm_io_handler, node);
+}
+
+int gunyah_vm_mmio_write(struct gunyah_vm *ghvm, u64 addr, u32 len, u64 data)
+{
+	struct gunyah_vm_io_handler *io_hdlr = NULL;
+	int ret;
+
+	down_read(&ghvm->mmio_handler_lock);
+	io_hdlr = gunyah_vm_mgr_find_io_hdlr(ghvm, addr, len, data);
+	if (!io_hdlr || !io_hdlr->ops || !io_hdlr->ops->write) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	ret = io_hdlr->ops->write(io_hdlr, addr, len, data);
+
+out:
+	up_read(&ghvm->mmio_handler_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gunyah_vm_mmio_write);
+
+int gunyah_vm_add_io_handler(struct gunyah_vm *ghvm,
+			     struct gunyah_vm_io_handler *io_hdlr)
+{
+	struct rb_node *found;
+
+	if (io_hdlr->datamatch &&
+	    (!io_hdlr->len || io_hdlr->len > sizeof(io_hdlr->data)))
+		return -EINVAL;
+
+	down_write(&ghvm->mmio_handler_lock);
+	found = rb_find_add(&io_hdlr->node, &ghvm->mmio_handler_root,
+			    gunyah_vm_io_handler_compare);
+	up_write(&ghvm->mmio_handler_lock);
+
+	return found ? -EEXIST : 0;
+}
+EXPORT_SYMBOL_GPL(gunyah_vm_add_io_handler);
+
+void gunyah_vm_remove_io_handler(struct gunyah_vm *ghvm,
+				 struct gunyah_vm_io_handler *io_hdlr)
+{
+	down_write(&ghvm->mmio_handler_lock);
+	rb_erase(&io_hdlr->node, &ghvm->mmio_handler_root);
+	up_write(&ghvm->mmio_handler_lock);
+}
+EXPORT_SYMBOL_GPL(gunyah_vm_remove_io_handler);
+
 static int gunyah_vm_rm_notification_status(struct gunyah_vm *ghvm, void *data)
 {
 	struct gunyah_rm_vm_status_payload *payload = data;
@@ -366,6 +478,8 @@ static __must_check struct gunyah_vm *gunyah_vm_alloc(struct gunyah_rm *rm)
 	mutex_init(&ghvm->resources_lock);
 	INIT_LIST_HEAD(&ghvm->resources);
 	INIT_LIST_HEAD(&ghvm->resource_tickets);
+	init_rwsem(&ghvm->mmio_handler_lock);
+	ghvm->mmio_handler_root = RB_ROOT;
 	INIT_LIST_HEAD(&ghvm->functions);
 	mutex_init(&ghvm->fn_lock);
 
diff --git a/drivers/virt/gunyah/vm_mgr.h b/drivers/virt/gunyah/vm_mgr.h
index b94f6d16b787..a26bf81e94fc 100644
--- a/drivers/virt/gunyah/vm_mgr.h
+++ b/drivers/virt/gunyah/vm_mgr.h
@@ -12,6 +12,7 @@
 #include <linux/list.h>
 #include <linux/mutex.h>
 #include <linux/notifier.h>
+#include <linux/rbtree.h>
 #include <linux/rwsem.h>
 #include <linux/wait.h>
 
@@ -37,6 +38,10 @@ struct gunyah_vm {
 	struct mutex resources_lock;
 	struct list_head resources;
 	struct list_head resource_tickets;
+	struct rb_root mmio_handler_root;
+	struct rw_semaphore mmio_handler_lock;
 };
 
+int gunyah_vm_mmio_write(struct gunyah_vm *ghvm, u64 addr, u32 len, u64 data);
+
 #endif
diff --git a/include/linux/gunyah_vm_mgr.h b/include/linux/gunyah_vm_mgr.h
index b02c6e89b207..635adcbcc7d4 100644
--- a/include/linux/gunyah_vm_mgr.h
+++ b/include/linux/gunyah_vm_mgr.h
@@ -133,4 +133,33 @@ int gunyah_vm_add_resource_ticket(struct gunyah_vm *ghvm,
 void gunyah_vm_remove_resource_ticket(struct gunyah_vm *ghvm,
 				      struct gunyah_vm_resource_ticket *ticket);
 
+/*
+ * gunyah_vm_io_handler contains the info about an io device and its associated
+ * addr and the ops associated with the io device.
+ */
+struct gunyah_vm_io_handler {
+	struct rb_node node;
+	u64 addr;
+
+	bool datamatch;
+	u8 len;
+	u64 data;
+	struct gunyah_vm_io_handler_ops *ops;
+};
+
+/*
+ * gunyah_vm_io_handler_ops contains function pointers associated with an iodevice.
+ */
+struct gunyah_vm_io_handler_ops {
+	int (*read)(struct gunyah_vm_io_handler *io_dev, u64 addr, u32 len,
+		    u64 data);
+	int (*write)(struct gunyah_vm_io_handler *io_dev, u64 addr, u32 len,
+		     u64 data);
+};
+
+int gunyah_vm_add_io_handler(struct gunyah_vm *ghvm,
+			     struct gunyah_vm_io_handler *io_dev);
+void gunyah_vm_remove_io_handler(struct gunyah_vm *ghvm,
+				 struct gunyah_vm_io_handler *io_dev);
+
 #endif

-- 
2.43.0