--- /dev/null
+// 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;
+}
+
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