xen: Port Xen grant table driver from mini-os

Make required updates to run on u-boot.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Anastasiia Lukianenko <anastasiia_lukianenko@epam.com>

board/xen/xenguest_arm64/xenguest_arm64.c

@@ -21,6 +21,7 @@
 
 #include <linux/compiler.h>
 
+#include <xen/gnttab.h>
 #include <xen/hvm.h>
 
 DECLARE_GLOBAL_DATA_PTR;
@@ -63,6 +64,8 @@ static int setup_mem_map(void)
 	struct fdt_resource res;
 	const void *blob = gd->fdt_blob;
 	u64 gfn;
+	phys_addr_t gnttab_base;
+	phys_size_t gnttab_sz;
 
 	/*
 	 * Add "magic" region which is used by Xen to provide some essentials
@@ -96,6 +99,16 @@ static int setup_mem_map(void)
 				PTE_BLOCK_INNER_SHARE);
 	i++;
 
+	/* Get Xen's suggested physical page assignments for the grant table. */
+	get_gnttab_base(&gnttab_base, &gnttab_sz);
+
+	xen_mem_map[i].virt = gnttab_base;
+	xen_mem_map[i].phys = gnttab_base;
+	xen_mem_map[i].size = gnttab_sz;
+	xen_mem_map[i].attrs = (PTE_BLOCK_MEMTYPE(MT_NORMAL) |
+				PTE_BLOCK_INNER_SHARE);
+	i++;
+
 	mem = get_next_memory_node(blob, -1);
 	if (mem < 0) {
 		printf("%s: Missing /memory node\n", __func__);

drivers/xen/Makefile

@@ -5,3 +5,4 @@
 obj-y += hypervisor.o
 obj-y += events.o
 obj-y += xenbus.o
+obj-y += gnttab.o

drivers/xen/gnttab.c

@@ -0,0 +1,216 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * (C) 2006 - Cambridge University
+ * (C) 2020 - EPAM Systems Inc.
+ *
+ * File: gnttab.c [1]
+ * Author: Steven Smith (sos22@cam.ac.uk)
+ * Changes: Grzegorz Milos (gm281@cam.ac.uk)
+ *
+ * Date: July 2006
+ *
+ * Description: Simple grant tables implementation. About as stupid as it's
+ * possible to be and still work.
+ *
+ * [1] - http://xenbits.xen.org/gitweb/?p=mini-os.git;a=summary
+ */
+#include <common.h>
+#include <linux/compiler.h>
+#include <log.h>
+#include <malloc.h>
+
+#include <asm/armv8/mmu.h>
+#include <asm/io.h>
+#include <asm/xen/system.h>
+
+#include <linux/bug.h>
+
+#include <xen/gnttab.h>
+#include <xen/hvm.h>
+
+#include <xen/interface/memory.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+#define NR_RESERVED_ENTRIES 8
+
+/* NR_GRANT_FRAMES must be less than or equal to that configured in Xen */
+#define NR_GRANT_FRAMES 1
+#define NR_GRANT_ENTRIES (NR_GRANT_FRAMES * PAGE_SIZE / sizeof(struct grant_entry_v1))
+
+static struct grant_entry_v1 *gnttab_table;
+static grant_ref_t gnttab_list[NR_GRANT_ENTRIES];
+
+static void put_free_entry(grant_ref_t ref)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	gnttab_list[ref] = gnttab_list[0];
+	gnttab_list[0]  = ref;
+	local_irq_restore(flags);
+}
+
+static grant_ref_t get_free_entry(void)
+{
+	unsigned int ref;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	ref = gnttab_list[0];
+	BUG_ON(ref < NR_RESERVED_ENTRIES || ref >= NR_GRANT_ENTRIES);
+	gnttab_list[0] = gnttab_list[ref];
+	local_irq_restore(flags);
+	return ref;
+}
+
+/**
+ * gnttab_grant_access() - Allow access to the given frame.
+ * The function creates an entry in the grant table according
+ * to the specified parameters.
+ * @domid: the id of the domain for which access is allowed
+ * @frame: the number of the shared frame
+ * @readonly: determines whether the frame is shared read-only or read-write
+ *
+ * Return: relevant grant reference
+ */
+grant_ref_t gnttab_grant_access(domid_t domid, unsigned long frame, int readonly)
+{
+	grant_ref_t ref;
+
+	ref = get_free_entry();
+	gnttab_table[ref].frame = frame;
+	gnttab_table[ref].domid = domid;
+	wmb();
+	readonly *= GTF_readonly;
+	gnttab_table[ref].flags = GTF_permit_access | readonly;
+
+	return ref;
+}
+
+/**
+ * gnttab_end_access() - End of memory sharing. The function invalidates
+ * the entry in the grant table.
+ */
+int gnttab_end_access(grant_ref_t ref)
+{
+	u16 flags, nflags;
+
+	BUG_ON(ref >= NR_GRANT_ENTRIES || ref < NR_RESERVED_ENTRIES);
+
+	nflags = gnttab_table[ref].flags;
+	do {
+		if ((flags = nflags) & (GTF_reading | GTF_writing)) {
+			printf("WARNING: g.e. still in use! (%x)\n", flags);
+			return 0;
+		}
+	} while ((nflags = synch_cmpxchg(&gnttab_table[ref].flags, flags, 0)) !=
+		 flags);
+
+	put_free_entry(ref);
+	return 1;
+}
+
+grant_ref_t gnttab_alloc_and_grant(void **map)
+{
+	unsigned long mfn;
+	grant_ref_t gref;
+
+	*map = (void *)memalign(PAGE_SIZE, PAGE_SIZE);
+	mfn = virt_to_mfn(*map);
+	gref = gnttab_grant_access(0, mfn, 0);
+	return gref;
+}
+
+static const char * const gnttabop_error_msgs[] = GNTTABOP_error_msgs;
+
+const char *gnttabop_error(int16_t status)
+{
+	status = -status;
+	if (status < 0 || status >= ARRAY_SIZE(gnttabop_error_msgs))
+		return "bad status";
+	else
+		return gnttabop_error_msgs[status];
+}
+
+/* Get Xen's suggested physical page assignments for the grant table. */
+void get_gnttab_base(phys_addr_t *gnttab_base, phys_size_t *gnttab_sz)
+{
+	const void *blob = gd->fdt_blob;
+	struct fdt_resource res;
+	int mem;
+
+	mem = fdt_node_offset_by_compatible(blob, -1, "xen,xen");
+	if (mem < 0) {
+		printf("No xen,xen compatible found\n");
+		BUG();
+	}
+
+	mem = fdt_get_resource(blob, mem, "reg", 0, &res);
+	if (mem == -FDT_ERR_NOTFOUND) {
+		printf("No grant table base in the device tree\n");
+		BUG();
+	}
+
+	*gnttab_base = (phys_addr_t)res.start;
+	if (gnttab_sz)
+		*gnttab_sz = (phys_size_t)(res.end - res.start + 1);
+
+	debug("FDT suggests grant table base at %llx\n",
+	      *gnttab_base);
+}
+
+void init_gnttab(void)
+{
+	struct xen_add_to_physmap xatp;
+	struct gnttab_setup_table setup;
+	xen_pfn_t frames[NR_GRANT_FRAMES];
+	int i, rc;
+
+	debug("%s\n", __func__);
+
+	for (i = NR_RESERVED_ENTRIES; i < NR_GRANT_ENTRIES; i++)
+		put_free_entry(i);
+
+	get_gnttab_base((phys_addr_t *)&gnttab_table, NULL);
+
+	for (i = 0; i < NR_GRANT_FRAMES; i++) {
+		xatp.domid = DOMID_SELF;
+		xatp.size = 0;
+		xatp.space = XENMAPSPACE_grant_table;
+		xatp.idx = i;
+		xatp.gpfn = PFN_DOWN((unsigned long)gnttab_table) + i;
+		rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp);
+		if (rc)
+			printf("XENMEM_add_to_physmap failed; status = %d\n",
+			       rc);
+		BUG_ON(rc != 0);
+	}
+
+	setup.dom = DOMID_SELF;
+	setup.nr_frames = NR_GRANT_FRAMES;
+	set_xen_guest_handle(setup.frame_list, frames);
+}
+
+void fini_gnttab(void)
+{
+	struct xen_remove_from_physmap xrtp;
+	struct gnttab_setup_table setup;
+	int i, rc;
+
+	debug("%s\n", __func__);
+
+	for (i = 0; i < NR_GRANT_FRAMES; i++) {
+		xrtp.domid = DOMID_SELF;
+		xrtp.gpfn = PFN_DOWN((unsigned long)gnttab_table) + i;
+		rc = HYPERVISOR_memory_op(XENMEM_remove_from_physmap, &xrtp);
+		if (rc)
+			printf("XENMEM_remove_from_physmap failed; status = %d\n",
+			       rc);
+		BUG_ON(rc != 0);
+	}
+
+	setup.dom = DOMID_SELF;
+	setup.nr_frames = 0;
+}
+

drivers/xen/hypervisor.c

@@ -21,6 +21,7 @@
 
 #include <xen/hvm.h>
 #include <xen/events.h>
+#include <xen/gnttab.h>
 #include <xen/xenbus.h>
 #include <xen/interface/memory.h>
 
@@ -238,5 +239,6 @@ void xen_init(void)
 	map_shared_info(NULL);
 	init_events();
 	init_xenbus();
+	init_gnttab();
 }
 

include/xen.h

@@ -8,7 +8,8 @@
 /**
  * xen_init() - Xen initialization
  *
- * Map Xen memory pages, initialize event handler and xenbus.
+ * Map Xen memory pages, initialize event handler and xenbus,
+ * setup the grant table.
  */
 void xen_init(void);
 

include/xen/gnttab.h

@@ -0,0 +1,24 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0
+ *
+ * (C) 2006, Steven Smith <sos22@cam.ac.uk>
+ * (C) 2006, Grzegorz Milos <gm281@cam.ac.uk>
+ * (C) 2020, EPAM Systems Inc.
+ */
+#ifndef __GNTTAB_H__
+#define __GNTTAB_H__
+
+#include <xen/interface/grant_table.h>
+
+void init_gnttab(void);
+void fini_gnttab(void);
+
+grant_ref_t gnttab_alloc_and_grant(void **map);
+grant_ref_t gnttab_grant_access(domid_t domid, unsigned long frame,
+				int readonly);
+int gnttab_end_access(grant_ref_t ref);
+const char *gnttabop_error(int16_t status);
+
+void get_gnttab_base(phys_addr_t *gnttab_base, phys_size_t *gnttab_sz);
+
+#endif /* !__GNTTAB_H__ */