--- /dev/null
+/*
+ * Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+#include <strings.h>
+#include <errno.h>
+#include <assert.h>
+#include <ipxe/io.h>
+#include <ipxe/xen.h>
+#include <ipxe/xengrant.h>
+
+/** @file
+ *
+ * Xen grant tables
+ *
+ */
+
+/** Grant table version to try setting
+ *
+ * Using version 1 grant tables limits guests to using 16TB of
+ * grantable RAM, and prevents the use of subpage grants. Some
+ * versions of the Xen hypervisor refuse to allow the grant table
+ * version to be set after the first grant references have been
+ * created, so the loaded operating system may be stuck with whatever
+ * choice we make here. We therefore currently use version 2 grant
+ * tables, since they give the most flexibility to the loaded OS.
+ *
+ * Current versions (7.2.0) of the Windows PV drivers have no support
+ * for version 2 grant tables, and will merrily create version 1
+ * entries in what the hypervisor believes to be a version 2 table.
+ * This causes some confusion.
+ *
+ * Avoid this problem by attempting to use version 1 tables, since
+ * otherwise we may render Windows unable to boot.
+ *
+ * Play nicely with other potential bootloaders by accepting either
+ * version 1 or version 2 grant tables (if we are unable to set our
+ * requested version).
+ */
+#define XENGRANT_TRY_VERSION 1
+
+/**
+ * Initialise grant table
+ *
+ * @v xen Xen hypervisor
+ * @ret rc Return status code
+ */
+int xengrant_init ( struct xen_hypervisor *xen ) {
+ struct gnttab_query_size size;
+ struct gnttab_set_version set_version;
+ struct gnttab_get_version get_version;
+ struct grant_entry_v1 *v1;
+ union grant_entry_v2 *v2;
+ unsigned int version;
+ int xenrc;
+ int rc;
+
+ /* Get grant table size */
+ size.dom = DOMID_SELF;
+ if ( ( xenrc = xengrant_query_size ( xen, &size ) ) != 0 ) {
+ rc = -EXEN ( xenrc );
+ DBGC ( xen, "XENGRANT could not get table size: %s\n",
+ strerror ( rc ) );
+ return rc;
+ }
+ xen->grant.len = ( size.nr_frames * PAGE_SIZE );
+
+ /* Set grant table version, if applicable */
+ set_version.version = XENGRANT_TRY_VERSION;
+ if ( ( xenrc = xengrant_set_version ( xen, &set_version ) ) != 0 ) {
+ rc = -EXEN ( xenrc );
+ DBGC ( xen, "XENGRANT could not set version %d: %s\n",
+ XENGRANT_TRY_VERSION, strerror ( rc ) );
+ /* Continue; use whatever version is current */
+ }
+
+ /* Get grant table version */
+ get_version.dom = DOMID_SELF;
+ get_version.pad = 0;
+ if ( ( xenrc = xengrant_get_version ( xen, &get_version ) ) == 0 ) {
+ version = get_version.version;
+ switch ( version ) {
+
+ case 0:
+ /* Version not yet specified: will be version 1 */
+ version = 1;
+ break;
+
+ case 1 :
+ /* Version 1 table: nothing special to do */
+ break;
+
+ case 2:
+ /* Version 2 table: configure shift appropriately */
+ xen->grant.shift = ( fls ( sizeof ( *v2 ) /
+ sizeof ( *v1 ) ) - 1 );
+ break;
+
+ default:
+ /* Unsupported version */
+ DBGC ( xen, "XENGRANT detected unsupported version "
+ "%d\n", version );
+ return -ENOTSUP;
+
+ }
+ } else {
+ rc = -EXEN ( xenrc );
+ DBGC ( xen, "XENGRANT could not get version (assuming v1): "
+ "%s\n", strerror ( rc ) );
+ version = 1;
+ }
+
+ DBGC ( xen, "XENGRANT using v%d table with %d entries\n",
+ version, xengrant_entries ( xen ) );
+ return 0;
+}
+
+/**
+ * Allocate grant references
+ *
+ * @v xen Xen hypervisor
+ * @v refs Grant references to fill in
+ * @v count Number of references
+ * @ret rc Return status code
+ */
+int xengrant_alloc ( struct xen_hypervisor *xen, grant_ref_t *refs,
+ unsigned int count ) {
+ struct grant_entry_header *hdr;
+ unsigned int entries = xengrant_entries ( xen );
+ unsigned int mask = ( entries - 1 );
+ unsigned int check = 0;
+ unsigned int avail;
+ unsigned int ref;
+
+ /* Fail unless we have enough references available */
+ avail = ( entries - xen->grant.used - GNTTAB_NR_RESERVED_ENTRIES );
+ if ( avail < count ) {
+ DBGC ( xen, "XENGRANT cannot allocate %d references (only %d "
+ "of %d available)\n", count, avail, entries );
+ return -ENOBUFS;
+ }
+ DBGC ( xen, "XENGRANT allocating %d references (from %d of %d "
+ "available)\n", count, avail, entries );
+
+ /* Update number of references used */
+ xen->grant.used += count;
+
+ /* Find unused references */
+ for ( ref = xen->grant.ref ; count ; ref = ( ( ref + 1 ) & mask ) ) {
+
+ /* Sanity check */
+ assert ( check++ < entries );
+
+ /* Skip reserved references */
+ if ( ref < GNTTAB_NR_RESERVED_ENTRIES )
+ continue;
+
+ /* Skip in-use references */
+ hdr = xengrant_header ( xen, ref );
+ if ( readw ( &hdr->flags ) & GTF_type_mask )
+ continue;
+ if ( readw ( &hdr->domid ) == DOMID_SELF )
+ continue;
+
+ /* Zero reference */
+ xengrant_zero ( xen, hdr );
+
+ /* Mark reference as in-use. We leave the flags as
+ * empty (to avoid creating a valid grant table entry)
+ * and set the domid to DOMID_SELF.
+ */
+ writew ( DOMID_SELF, &hdr->domid );
+ DBGC2 ( xen, "XENGRANT allocated ref %d\n", ref );
+
+ /* Record reference */
+ refs[--count] = ref;
+ }
+
+ /* Update cursor */
+ xen->grant.ref = ref;
+
+ return 0;
+}
+
+/**
+ * Free grant references
+ *
+ * @v xen Xen hypervisor
+ * @v refs Grant references
+ * @v count Number of references
+ */
+void xengrant_free ( struct xen_hypervisor *xen, grant_ref_t *refs,
+ unsigned int count ) {
+ struct grant_entry_header *hdr;
+ unsigned int ref;
+ unsigned int i;
+
+ /* Free references */
+ for ( i = 0 ; i < count ; i++ ) {
+
+ /* Sanity check */
+ ref = refs[i];
+ assert ( ref < xengrant_entries ( xen ) );
+
+ /* Zero reference */
+ hdr = xengrant_header ( xen, ref );
+ xengrant_zero ( xen, hdr );
+ DBGC2 ( xen, "XENGRANT freed ref %d\n", ref );
+ }
+}
Code Review / kvmfornfv.git / blobdiff