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Subject[PATCH v2 18/18] powerpc/vas: Add support for user receive window
Date
Add support for user space receive window (for the Fast thread-wakeup
coprocessor type)

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
---
arch/powerpc/platforms/powernv/vas-window.c | 59 +++++++++++++++++++++++++----
1 file changed, 52 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c
index 1d08b64..99642ec 100644
--- a/arch/powerpc/platforms/powernv/vas-window.c
+++ b/arch/powerpc/platforms/powernv/vas-window.c
@@ -16,7 +16,8 @@
#include <linux/log2.h>
#include <linux/rcupdate.h>
#include <linux/cred.h>
-
+#include <asm/switch_to.h>
+#include <asm/ppc-opcode.h>
#include "vas.h"
#include "copy-paste.h"

@@ -602,6 +603,32 @@ static void put_rx_win(struct vas_window *rxwin)
}

/*
+ * Find the user space receive window given the @pswid.
+ * - We must have a valid vasid and it must belong to this instance.
+ * (so both send and receive windows are on the same VAS instance)
+ * - The window must refer to an OPEN, FTW, RECEIVE window.
+ *
+ * NOTE: We access ->windows[] table and assume that vinst->mutex is held.
+ */
+static struct vas_window *get_user_rxwin(struct vas_instance *vinst, u32 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);
+
+ return rxwin;
+}
+
+/*
* Get the VAS receive window associated with NX engine identified
* by @cop and if applicable, @pswid.
*
@@ -614,10 +641,10 @@ static struct vas_window *get_vinst_rxwin(struct vas_instance *vinst,

mutex_lock(&vinst->mutex);

- if (cop == VAS_COP_TYPE_842 || cop == VAS_COP_TYPE_842_HIPRI)
- rxwin = vinst->rxwin[cop] ?: ERR_PTR(-EINVAL);
+ if (cop == VAS_COP_TYPE_FTW)
+ rxwin = get_user_rxwin(vinst, pswid);
else
- rxwin = ERR_PTR(-EINVAL);
+ rxwin = vinst->rxwin[cop] ?: ERR_PTR(-EINVAL);

if (!IS_ERR(rxwin))
atomic_inc(&rxwin->num_txwins);
@@ -941,10 +968,9 @@ static void init_winctx_for_txwin(struct vas_window *txwin,
winctx->tx_word_mode = txattr->tx_win_ord_mode;
winctx->rsvd_txbuf_count = txattr->rsvd_txbuf_count;

- if (winctx->nx_win) {
+ winctx->intr_disable = true;
+ if (winctx->nx_win)
winctx->data_stamp = true;
- winctx->intr_disable = true;
- }

winctx->lpid = txattr->lpid;
winctx->pidr = txattr->pidr;
@@ -989,6 +1015,14 @@ struct vas_window *vas_tx_win_open(int vasid, enum vas_cop_type cop,
if (!tx_win_args_valid(cop, attr))
return ERR_PTR(-EINVAL);

+ /*
+ * If caller did not specify a vasid but specified the PSWID of a
+ * receive window (applicable only to FTW windows), use the vasid
+ * from that receive window.
+ */
+ if (vasid == -1 && attr->pswid)
+ decode_pswid(attr->pswid, &vasid, NULL);
+
vinst = find_vas_instance(vasid);
if (!vinst) {
pr_devel("vasid %d not found!\n", vasid);
@@ -1037,6 +1071,17 @@ struct vas_window *vas_tx_win_open(int vasid, enum vas_cop_type cop,

set_vinst_win(vinst, txwin);

+ set_thread_used_vas();
+
+ /*
+ * Even a process that has no foreign real address mapping can use
+ * an unpaired COPY instruction (to no real effect). Issue CP_ABORT
+ * to clear any pending COPY and prevent a covert channel.
+ *
+ * __switch_to() will issue CP_ABORT on future context switches.
+ */
+ asm volatile(PPC_CP_ABORT);
+
return txwin;

free_window:
--
2.7.4
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