[Skiboot] [PATCH skiboot v2] npu2: Add XTS_BDF_MAP wildcard refcount

[Alexey Kardashevskiy]

Currently PID wildcard is programmed into the NPU once and never cleared
up. This works for the bare metal as MSR does not change while the host
OS is running.

However with the device virtualization, we need to keep track of wildcard
entries use and clear them up before switching a GPU from a host to
a guest or vice versa.

This adds refcount to a NPU2, one counter per wildcard entry. The index
is a short lparid which is allocated in opal_npu_map_lpar() and should be
smaller than NPU2_XTS_BDF_MAP_SIZE.

Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
---
Changes:
v2:
* fixed error handling opal_npu_init_context when checking xts_bdf_pid
---
 include/npu2.h |  2 ++
 hw/npu2.c      | 42 +++++++++++++++++++++++++++++++++---------
 2 files changed, 35 insertions(+), 9 deletions(-)

diff --git a/include/npu2.h b/include/npu2.h
index 1de963d..d05c001 100644
--- a/include/npu2.h
+++ b/include/npu2.h
@@ -19,6 +19,7 @@
 
 #include <pci.h>
 #include <phys-map.h>
+#include <npu2-regs.h>
 
 /* Debugging options */
 #define NPU2DBG(p, fmt, a...)	prlog(PR_DEBUG, "NPU%d: " fmt, \
@@ -162,6 +163,7 @@ struct npu2 {
 	uint32_t	total_devices;
 	struct npu2_dev	*devices;
 	enum phys_map_type gpu_map_type;
+	int		ctx_ref[NPU2_XTS_BDF_MAP_SIZE];
 
 	/* IODA cache */
 	uint64_t	lxive_cache[8];
diff --git a/hw/npu2.c b/hw/npu2.c
index ba1264b..80043e3 100644
--- a/hw/npu2.c
+++ b/hw/npu2.c
@@ -28,7 +28,6 @@
 #include <ccan/str/str.h>
 #include <ccan/array_size/array_size.h>
 #include <affinity.h>
-#include <npu2-regs.h>
 #include <npu2.h>
 #include <lock.h>
 #include <xscom.h>
@@ -2097,6 +2096,11 @@ static int64_t opal_npu_init_context(uint64_t phb_id, int pasid __unused,
 	}
 
 	id = GETFIELD(NPU2_XTS_BDF_MAP_LPARSHORT, xts_bdf);
+	if (id >= NPU2_XTS_BDF_MAP_SIZE) {
+		NPU2ERR(p, "Out of bounds id=%d\n", id);
+		id = OPAL_INTERNAL_ERROR;
+		goto out;
+	}
 	NPU2DBG(p, "Found LPARSHORT = 0x%x for BDF = 0x%03llx\n", id, bdf);
 
 	/* Enable this mapping for both real and virtual addresses */
@@ -2129,14 +2133,20 @@ static int64_t opal_npu_init_context(uint64_t phb_id, int pasid __unused,
 		    GETFIELD(NPU2_XTS_PID_MAP_MSR, xts_bdf_pid)) {
 			NPU2ERR(p, "%s: Unexpected MSR value\n", __func__);
 			id = OPAL_PARAMETER;
+			goto out;
+		} else if (!p->ctx_ref[id]) {
+			NPU2ERR(p, "%s: Unexpected mapping\n", __func__);
+			id = OPAL_INTERNAL_ERROR;
+			goto out;
 		}
-
-		goto out;
 	}
 
 	/* Write the entry */
-	NPU2DBG(p, "XTS_PID_MAP[%03d] = 0x%08llx\n", id, xts_bdf_pid);
-	npu2_write(p, NPU2_XTS_PID_MAP + id*0x20, xts_bdf_pid);
+	if (!p->ctx_ref[id]) {
+		NPU2DBG(p, "XTS_PID_MAP[%03d] = 0x%08llx\n", id, xts_bdf_pid);
+		npu2_write(p, NPU2_XTS_PID_MAP + id*0x20, xts_bdf_pid);
+	}
+	++p->ctx_ref[id];
 
 	if (!GETFIELD(NPU2_XTS_BDF_MAP_VALID, xts_bdf)) {
 		xts_bdf = SETFIELD(NPU2_XTS_BDF_MAP_VALID, xts_bdf, 1);
@@ -2155,7 +2165,7 @@ static int opal_npu_destroy_context(uint64_t phb_id, uint64_t pid __unused,
 	struct phb *phb = pci_get_phb(phb_id);
 	struct npu2 *p;
 	uint64_t xts_bdf;
-	int rc = 0;
+	int rc = 0, id;
 
 	if (!phb || phb->phb_type != phb_type_npu_v2)
 		return OPAL_PARAMETER;
@@ -2172,10 +2182,24 @@ static int opal_npu_destroy_context(uint64_t phb_id, uint64_t pid __unused,
 	}
 
 	/*
-	 * The bdf/pid table only contains wildcard entries, so we don't
-	 * need to remove anything here.
+	 * The bdf/pid table contains wildcard entries and MSR bits which
+	 * we need to clear between switching a device from a host to a guest
+	 * or vice versa.
 	 */
-
+	id = GETFIELD(NPU2_XTS_BDF_MAP_LPARSHORT, xts_bdf);
+	if (id >= NPU2_XTS_BDF_MAP_SIZE) {
+		NPU2ERR(p, "Out of bounds id=%d\n", id);
+		rc = OPAL_INTERNAL_ERROR;
+	} else {
+		--p->ctx_ref[id];
+		rc = p->ctx_ref[id]; /* For debug */
+		if (p->ctx_ref[id] < 0) {
+			rc = OPAL_INTERNAL_ERROR; /* Sanity check */
+		} else if (!p->ctx_ref[id]) {
+			NPU2DBG(p, "XTS_PID_MAP[%03d] = 0 (destroy)\n", id);
+			npu2_write(p, NPU2_XTS_PID_MAP + id*0x20, 0);
+		}
+	}
 	unlock(&p->lock);
 	return rc;
 }
-- 
2.17.1