[PATCH v6 09/17] powerpc/vas: Define vas_rx_win_open() interface

[Sukadev Bhattiprolu]

Define the vas_rx_win_open() interface. This interface is intended to be
used by the Nest Accelerator (NX) driver(s) to setup receive windows for
one or more NX engines (which implement compression/encryption algorithms
in the hardware).

Follow-on patches will provide an interface to close the window and to open
a send window that kenrel subsystems can use to access the NX engines.

The interface to open a receive window is expected to be invoked for each
instance of VAS in the system.

Signed-off-by: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx>
---

Changelog[v6]:
	- Add support for FTW windows

Changelog[v4]:
	- Export the symbols

Changelog[v3]:
	- Fault receive windows must enable interrupts and disable
	  notifications. NX Windows are opposite.
	- Use macros rather than enum for threshold-control mode
	- Ignore irq_ports for in-kernel windows. They are needed for
	  user space windows and will be added later
---
 arch/powerpc/include/asm/vas.h              |  47 ++++
 arch/powerpc/platforms/powernv/vas-window.c | 357 +++++++++++++++++++++++++++-
 arch/powerpc/platforms/powernv/vas.h        |  14 ++
 3 files changed, 417 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/vas.h b/arch/powerpc/include/asm/vas.h
index 30667db..a3778d7 100644
--- a/arch/powerpc/include/asm/vas.h
+++ b/arch/powerpc/include/asm/vas.h
@@ -35,6 +35,36 @@ enum vas_cop_type {
 };
 
 /*
+ * Receive window attributes specified by the (in-kernel) owner of window.
+ */
+struct vas_rx_win_attr {
+	void *rx_fifo;
+	int rx_fifo_size;
+	int wcreds_max;
+
+	bool pin_win;
+	bool rej_no_credit;
+	bool tx_wcred_mode;
+	bool rx_wcred_mode;
+	bool tx_win_ord_mode;
+	bool rx_win_ord_mode;
+	bool data_stamp;
+	bool nx_win;
+	bool fault_win;
+	bool user_win;
+	bool notify_disable;
+	bool intr_disable;
+	bool notify_early;
+
+	int lnotify_lpid;
+	int lnotify_pid;
+	int lnotify_tid;
+	uint32_t pswid;
+
+	int tc_mode;
+};
+
+/*
  * Return a system-wide unique id for the VAS window @win.
  */
 extern uint32_t vas_win_id(struct vas_window *win);
@@ -44,4 +74,21 @@ extern uint32_t vas_win_id(struct vas_window *win);
  * can map that address into their address space.
  */
 extern uint64_t vas_win_paste_addr(struct vas_window *win);
+
+/*
+ * Helper to initialize receive window attributes to defaults for an
+ * NX window.
+ */
+extern void vas_init_rx_win_attr(struct vas_rx_win_attr *rxattr,
+				enum vas_cop_type cop);
+
+/*
+ * Open a VAS receive window for the instance of VAS identified by @vasid
+ * Use @attr to initialize the attributes of the window.
+ *
+ * Return a handle to the window or ERR_PTR() on error.
+ */
+extern struct vas_window *vas_rx_win_open(int vasid, enum vas_cop_type cop,
+			struct vas_rx_win_attr *attr);
+
 #endif /* _MISC_VAS_H */
diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c
index 42c1d4f..ff64022 100644
--- a/arch/powerpc/platforms/powernv/vas-window.c
+++ b/arch/powerpc/platforms/powernv/vas-window.c
@@ -12,6 +12,8 @@
 #include <linux/slab.h>
 #include <linux/io.h>
 #include <linux/log2.h>
+#include <linux/rcupdate.h>
+#include <linux/cred.h>
 
 #include "vas.h"
 
@@ -544,7 +546,7 @@ void vas_window_free(struct vas_window *window)
 	vas_release_window_id(&vinst->ida, winid);
 }
 
-struct vas_window *vas_window_alloc(struct vas_instance *vinst)
+static struct vas_window *vas_window_alloc(struct vas_instance *vinst)
 {
 	int winid;
 	struct vas_window *window;
@@ -570,6 +572,359 @@ struct vas_window *vas_window_alloc(struct vas_instance *vinst)
 	return ERR_PTR(-ENOMEM);
 }
 
+/*
+ * Check if current task has permissions to pair with the process that
+ * opened the receive window @rxwin. For now the check is based on
+ * kill_ok_by_cred() - i.e equivalent to current task being able to
+ * send a signal to owner of @rxwin.
+ */
+static bool valid_permissions(struct vas_window *rxwin)
+{
+	bool rc;
+	struct task_struct *wtask;
+	const struct cred *txcred, *rxcred;
+
+	rcu_read_lock();
+	wtask = find_task_by_vpid(rxwin->pid);
+
+	/*
+	 * CHECK: Don't need to get_task_struct(wtask) since we hold
+	 *	  RCU till we complete the uid checks? Since rxwin is
+	 *	  open, the task has not exited.
+	 */
+
+	txcred = current_cred();
+	rxcred = __task_cred(wtask);
+
+	rc = false;
+	if (uid_eq(txcred->euid, rxcred->suid) ||
+			uid_eq(txcred->euid, rxcred->uid) ||
+			uid_eq(txcred->uid, rxcred->suid) ||
+			uid_eq(txcred->uid, rxcred->uid) ||
+			capable(CAP_KILL))
+		rc = true;
+
+	rcu_read_unlock();
+
+	return rc;
+}
+
+/*
+ * Find the user space receive window given the @pswid.
+ *
+ * The pswid, aka rx_win_handle, comes from user space so we should
+ * validate it carefully.
+ *      - We must have a valid vasid and it must belong to this instance.
+ *      - The window must refer to an OPEN, FTW, RECEIVE window.
+ *      - Calling process must have "kill" capabilities to the process
+ *        that opened/owns the receive window.
+ *      - Anything else?
+ *
+ * NOTE: We access ->windows[] table and assume that vinst->mutex is held.
+ */
+struct vas_window *get_user_rxwin(struct vas_instance *vinst, uint32_t pswid)
+{
+	int vasid, winid;
+	struct vas_window *rxwin;
+
+	decode_pswid(pswid, &vasid, &winid);
+
+	if (vinst->vas_id != vasid)
+		return ERR_PTR(-EINVAL);
+
+	rxwin = vinst->windows[winid];
+
+	if (!rxwin || rxwin->tx_win || rxwin->cop != VAS_COP_TYPE_FTW)
+		return ERR_PTR(-EINVAL);
+
+	if (!valid_permissions(rxwin))
+		return ERR_PTR(-EACCES);
+
+	return rxwin;
+}
+
+/*
+ * Get the VAS receive window associated with NX engine identified
+ * by @cop and if applicable, @pswid.
+ *
+ * See also function header of set_vinst_win().
+ */
+struct vas_window *get_vinst_rxwin(struct vas_instance *vinst,
+			enum vas_cop_type cop, uint32_t pswid)
+{
+	struct vas_window *rxwin;
+
+	mutex_lock(&vinst->mutex);
+
+	if (cop == VAS_COP_TYPE_FTW)
+		rxwin = get_user_rxwin(vinst, pswid);
+	else
+		rxwin = vinst->rxwin[cop] ?: ERR_PTR(-EINVAL);
+
+	if (!IS_ERR(rxwin))
+		atomic_inc(&rxwin->num_txwins);
+
+	mutex_unlock(&vinst->mutex);
+
+	return rxwin;
+}
+
+/*
+ * We have two tables of windows in a VAS instance. The first one,
+ * ->windows[], contains all the windows in the instance and allows
+ * looking up a window by its id. It is used to look up send windows
+ * during fault handling and receive windows when pairing user space
+ * send/receive windows.
+ *
+ * The second table, ->rxwin[], contains receive windows that are
+ * associated with NX engines. This table has VAS_COP_TYPE_MAX
+ * entries and is used to look up a receive window by its
+ * coprocessor type.
+ *
+ * Here, we save @window in the ->windows[] table. If it is a receive
+ * window, we also save the window in the ->rxwin[] table.
+ */
+static void set_vinst_win(struct vas_instance *vinst,
+			struct vas_window *window)
+{
+	int id = window->winid;
+
+	mutex_lock(&vinst->mutex);
+
+	/*
+	 * There should only be one receive window for a coprocessor type
+	 * unless its a user (FTW) window.
+	 */
+	if (!window->user_win && !window->tx_win) {
+		WARN_ON_ONCE(vinst->rxwin[window->cop]);
+		vinst->rxwin[window->cop] = window;
+	}
+
+	WARN_ON_ONCE(vinst->windows[id] != NULL);
+	vinst->windows[id] = window;
+
+	mutex_unlock(&vinst->mutex);
+}
+
+/*
+ * Clear this window from the table(s) of windows for this VAS instance.
+ * See also function header of set_vinst_win().
+ */
+void clear_vinst_win(struct vas_window *window)
+{
+	int id = window->winid;
+	struct vas_instance *vinst = window->vinst;
+
+	mutex_lock(&vinst->mutex);
+
+	if (!window->tx_win) {
+		WARN_ON_ONCE(!vinst->rxwin[window->cop]);
+		vinst->rxwin[window->cop] = NULL;
+	}
+
+	WARN_ON_ONCE(vinst->windows[id] != window);
+	vinst->windows[id] = NULL;
+
+	mutex_unlock(&vinst->mutex);
+}
+
+static void init_winctx_for_rxwin(struct vas_window *rxwin,
+			struct vas_rx_win_attr *rxattr,
+			struct vas_winctx *winctx)
+{
+	/*
+	 * We first zero (memset()) all fields and only set non-zero fields.
+	 * Following fields are 0/false but maybe deserve a comment:
+	 *
+	 *	->notify_os_intr_reg	In powerNV, send intrs to HV
+	 *	->notify_disable	False for NX windows
+	 *	->intr_disable		False for Fault Windows
+	 *	->xtra_write		False for NX windows
+	 *	->notify_early		NA for NX windows
+	 *	->rsvd_txbuf_count	NA for Rx windows
+	 *	->lpid, ->pid, ->tid	NA for Rx windows
+	 */
+
+	memset(winctx, 0, sizeof(struct vas_winctx));
+
+	winctx->rx_fifo = rxattr->rx_fifo;
+	winctx->rx_fifo_size = rxattr->rx_fifo_size;
+	winctx->wcreds_max = rxattr->wcreds_max ?: VAS_WCREDS_DEFAULT;
+	winctx->pin_win = rxattr->pin_win;
+
+	winctx->nx_win = rxattr->nx_win;
+	winctx->fault_win = rxattr->fault_win;
+	winctx->rx_word_mode = rxattr->rx_win_ord_mode;
+	winctx->tx_word_mode = rxattr->tx_win_ord_mode;
+	winctx->rx_wcred_mode = rxattr->rx_wcred_mode;
+	winctx->tx_wcred_mode = rxattr->tx_wcred_mode;
+
+	if (winctx->nx_win) {
+		winctx->data_stamp = true;
+		winctx->intr_disable = true;
+		winctx->pin_win = true;
+
+		WARN_ON_ONCE(winctx->fault_win);
+		WARN_ON_ONCE(!winctx->rx_word_mode);
+		WARN_ON_ONCE(!winctx->tx_word_mode);
+		WARN_ON_ONCE(winctx->notify_after_count);
+	} else if (winctx->fault_win) {
+		winctx->notify_disable = true;
+	} else if (winctx->user_win) {
+		/*
+		 * Section 1.8.1 Low Latency Core-Core Wake up of
+		 * the VAS workbook:
+		 *
+		 *      - disable credit checks ([tr]x_wcred_mode = false)
+		 *      - disable FIFO writes
+		 *      - enable ASB_Notify, disable interrupt
+		 */
+		winctx->fifo_disable = true;
+		winctx->intr_disable = true;
+		winctx->rx_fifo = NULL;
+	}
+
+	winctx->lnotify_lpid = rxattr->lnotify_lpid;
+	winctx->lnotify_pid = rxattr->lnotify_pid;
+	winctx->lnotify_tid = rxattr->lnotify_tid;
+	winctx->pswid = rxattr->pswid;
+	winctx->dma_type = VAS_DMA_TYPE_INJECT;
+	winctx->tc_mode = rxattr->tc_mode;
+
+	winctx->min_scope = VAS_SCOPE_LOCAL;
+	winctx->max_scope = VAS_SCOPE_VECTORED_GROUP;
+}
+
+static bool rx_win_args_valid(enum vas_cop_type cop,
+			struct vas_rx_win_attr *attr)
+{
+	dump_rx_win_attr(attr);
+
+	if (cop >= VAS_COP_TYPE_MAX)
+		return false;
+
+	if (cop != VAS_COP_TYPE_FTW &&
+				attr->rx_fifo_size < VAS_RX_FIFO_SIZE_MIN)
+		return false;
+
+	if (attr->rx_fifo_size > VAS_RX_FIFO_SIZE_MAX)
+		return false;
+
+	if (attr->nx_win) {
+		/* cannot be fault or user window if it is nx */
+		if (attr->fault_win || attr->user_win)
+			return false;
+		/*
+		 * Section 3.1.4.32: NX Windows must not disable notification,
+		 *	and must not enable interrupts or early notification.
+		 */
+		if (attr->notify_disable || !attr->intr_disable ||
+				attr->notify_early)
+			return false;
+	} else if (attr->fault_win) {
+		/* cannot be both fault and user window */
+		if (attr->user_win)
+			return false;
+
+		/*
+		 * Section 3.1.4.32: Fault windows must disable notification
+		 *	but not interrupts.
+		 */
+		if (!attr->notify_disable || attr->intr_disable)
+			return false;
+
+	} else if (attr->user_win) {
+		/*
+		 * User receive windows are only for fast-thread-wakeup
+		 * (FTW). They don't need a FIFO and must disable interrupts
+		 */
+		if (attr->rx_fifo || attr->rx_fifo_size || !attr->intr_disable)
+			return false;
+	} else {
+		/* Rx window must be one of NX or Fault or User window. */
+		return false;
+	}
+
+	return true;
+}
+
+void vas_init_rx_win_attr(struct vas_rx_win_attr *rxattr, enum vas_cop_type cop)
+{
+	memset(rxattr, 0, sizeof(*rxattr));
+
+	if (cop == VAS_COP_TYPE_842 || cop == VAS_COP_TYPE_842_HIPRI) {
+		rxattr->pin_win = true;
+		rxattr->nx_win = true;
+		rxattr->fault_win = false;
+		rxattr->intr_disable = true;
+		rxattr->rx_wcred_mode = true;
+		rxattr->tx_wcred_mode = true;
+		rxattr->rx_win_ord_mode = true;
+		rxattr->tx_win_ord_mode = true;
+	} else if (cop == VAS_COP_TYPE_FAULT) {
+		rxattr->pin_win = true;
+		rxattr->fault_win = true;
+		rxattr->notify_disable = true;
+		rxattr->rx_wcred_mode = true;
+		rxattr->tx_wcred_mode = true;
+		rxattr->rx_win_ord_mode = true;
+		rxattr->tx_win_ord_mode = true;
+	} else if (cop == VAS_COP_TYPE_FTW) {
+		rxattr->user_win = true;
+		rxattr->intr_disable = true;
+
+		/*
+		 * As noted in the VAS Workbook we disable credit checks.
+		 * If we enable credit checks in the future, we must also
+		 * implement a mechanism to return the user credits or new
+		 * paste operations will fail.
+		 */
+	}
+}
+EXPORT_SYMBOL_GPL(vas_init_rx_win_attr);
+
+struct vas_window *vas_rx_win_open(int vasid, enum vas_cop_type cop,
+			struct vas_rx_win_attr *rxattr)
+{
+	struct vas_instance *vinst;
+	struct vas_window *rxwin;
+	struct vas_winctx winctx;
+
+	if (!vas_initialized())
+		return ERR_PTR(-EAGAIN);
+
+	if (!rx_win_args_valid(cop, rxattr))
+		return ERR_PTR(-EINVAL);
+
+	vinst = find_vas_instance(vasid);
+	if (!vinst) {
+		pr_devel("VAS: vasid %d not found!\n", vasid);
+		return ERR_PTR(-EINVAL);
+	}
+	pr_devel("VAS: Found instance %d\n", vasid);
+
+	rxwin = vas_window_alloc(vinst);
+	if (IS_ERR(rxwin)) {
+		pr_devel("VAS: Unable to allocate memory for Rx window\n");
+		return rxwin;
+	}
+
+	rxwin->tx_win = false;
+	rxwin->nx_win = rxattr->nx_win;
+	rxwin->user_win = rxattr->user_win;
+	rxwin->cop = cop;
+	if (rxattr->user_win)
+		rxwin->pid = task_pid_vnr(current);
+
+	init_winctx_for_rxwin(rxwin, rxattr, &winctx);
+	init_winctx_regs(rxwin, &winctx);
+
+	set_vinst_win(vinst, rxwin);
+
+	return rxwin;
+}
+EXPORT_SYMBOL_GPL(vas_rx_win_open);
+
 /* stub for now */
 int vas_win_close(struct vas_window *window)
 {
diff --git a/arch/powerpc/platforms/powernv/vas.h b/arch/powerpc/platforms/powernv/vas.h
index 3eadf90..61fd80f 100644
--- a/arch/powerpc/platforms/powernv/vas.h
+++ b/arch/powerpc/platforms/powernv/vas.h
@@ -289,6 +289,9 @@ enum vas_notify_after_count {
 /*
  * One per instance of VAS. Each instance will have a separate set of
  * receive windows, one per coprocessor type.
+ *
+ * See also function header of set_vinst_win() for details on ->windows[]
+ * and ->rxwin[] tables.
  */
 struct vas_instance {
 	int vas_id;
@@ -397,6 +400,16 @@ extern struct vas_instance *find_vas_instance(int vasid);
 #define VREG(r)		VREG_SFX(r, _OFFSET)
 
 #ifdef vas_debug
+static inline void dump_rx_win_attr(struct vas_rx_win_attr *attr)
+{
+	pr_err("VAS: fault %d, notify %d, intr %d early %d\n",
+			attr->fault_win, attr->notify_disable,
+			attr->intr_disable, attr->notify_early);
+
+	pr_err("VAS: rx_fifo_size %d, max value %d\n",
+				attr->rx_fifo_size, VAS_RX_FIFO_SIZE_MAX);
+}
+
 static inline void vas_log_write(struct vas_window *win, char *name,
 			void *regptr, uint64_t val)
 {
@@ -409,6 +422,7 @@ static inline void vas_log_write(struct vas_window *win, char *name,
 #else	/* vas_debug */
 
 #define vas_log_write(win, name, reg, val)
+#define dump_rx_win_attr(attr)
 
 #endif	/* vas_debug */
 
-- 
2.7.4