Rationalize max_grant_frames and max_maptrack_frames handling

Xen used to have single, system-wide limits for the number of grant
frames and maptrack frames a guest was allowed to create. Increasing
or decreasing this single limit on the Xen command-line would change
the limit for all guests on the system.

Later, per-domain limits for these values was created. The system-wide
limits became strict limits: domains could not be created with higher
limits, but could be created with lower limits. However, that change
also introduced a range of different "default" values into various
places in the toolstack:

- The python libxc bindings hard-coded these values to 32 and 1024,
  respectively
- The libxl default values are 32 and 1024 respectively.
- xl will use the libxl default for maptrack, but does its own default
  calculation for grant frames: either 32 or 64, based on the max
  possible mfn.

These defaults interact poorly with the hypervisor command-line limit:

- The hypervisor command-line limit cannot be used to raise the limit
  for all guests anymore, as the default in the toolstack will
  effectively override this.
- If you use the hypervisor command-line limit to *reduce* the limit,
  then the "default" values generated by the toolstack are too high,
  and all guest creations will fail.

In other words, the toolstack defaults require any change to be
effected by having the admin explicitly specify a new value in every
guest.

In order to address this, have grant_table_init treat negative values
for max_grant_frames and max_maptrack_frames as instructions to use the
system-wide default, and have all the above toolstacks default to passing
-1 unless a different value is explicitly configured.

This restores the old behavior in that changing the hypervisor command-line
option can change the behavior for all guests, while retaining the ability
to set per-guest values.  It also removes the bug that reducing the
system-wide max will cause all domains without explicit limits to fail.

NOTE: - The Ocaml bindings require the caller to always specify a value,
        and the code to start a xenstored stubdomain hard-codes these to 4
	and 128 respectively; this behavour will not be modified.

Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Juergen Gross <jgross@suse.com>
Acked-by: Wei Liu <wl@xen.org>
Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

diff --git a/docs/man/xl.conf.5.pod b/docs/man/xl.conf.5.pod
index 962144e38ee9676ce922595cee56b7203ddc823a..207ab3e77a7b0c26288ce8af2b75b7896c65a253 100644 (file)
--- a/docs/man/xl.conf.5.pod
+++ b/docs/man/xl.conf.5.pod
@@ -81,13 +81,15 @@ Default: C</var/lock/xl>
 
 Sets the default value for the C<max_grant_frames> domain config value.
 
-Default: C<32> on hosts up to 16TB of memory, C<64> on hosts larger than 16TB
+Default: value of Xen command line B<gnttab_max_frames> parameter (or its
+default value if unspecified).
 
 =item B<max_maptrack_frames=NUMBER>
 
 Sets the default value for the C<max_maptrack_frames> domain config value.
 
-Default: C<1024>
+Default: value of Xen command line B<gnttab_max_maptrack_frames>
+parameter (or its default value if unspecified).
 
 =item B<vif.default.script="PATH">
 

diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 49b56fa1a36c382af2cb75a8ba7bf6b85692172d..54abb9db1f93786045828d88a7018bc429498c21 100644 (file)
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -364,8 +364,17 @@
  */
 #define LIBXL_HAVE_BUILDINFO_GRANT_LIMITS 1
 
-#define LIBXL_MAX_GRANT_FRAMES_DEFAULT 32
-#define LIBXL_MAX_MAPTRACK_FRAMES_DEFAULT 1024
+#define LIBXL_MAX_GRANT_DEFAULT (~(uint32_t)0)
+#define LIBXL_MAX_GRANT_FRAMES_DEFAULT 32 /* deprecated */
+#define LIBXL_MAX_MAPTRACK_FRAMES_DEFAULT 1024 /* deprecated */
+/*
+ * LIBXL_HAVE_BUILDINFO_GRANT_DEFAULT indicates that the default
+ * values of max_grant_frames and max_maptrack_frames fields in
+ * libxl_domain_build_info are the special sentinel value
+ * LIBXL_MAX_GRANT_DEFAULT rather than the fixed values above.
+ * This means to use the hypervisor's default.
+ */
+#define LIBXL_HAVE_BUILDINFO_GRANT_DEFAULT 1
 
 /*
  * LIBXL_HAVE_BUILDINFO_* indicates that libxl_domain_build_info has

diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 0546d7865ab85cd1778f9a78622affe5192a9f14..7921950f6afc801be4a9c32055a8379e00390a36 100644 (file)
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -511,8 +511,8 @@ libxl_domain_build_info = Struct("domain_build_info",[
 
     ("vnuma_nodes", Array(libxl_vnode_info, "num_vnuma_nodes")),
 
-    ("max_grant_frames",    uint32, {'init_val': 'LIBXL_MAX_GRANT_FRAMES_DEFAULT'}),
-    ("max_maptrack_frames", uint32, {'init_val': 'LIBXL_MAX_MAPTRACK_FRAMES_DEFAULT'}),
+    ("max_grant_frames",    uint32, {'init_val': 'LIBXL_MAX_GRANT_DEFAULT'}),
+    ("max_maptrack_frames", uint32, {'init_val': 'LIBXL_MAX_GRANT_DEFAULT'}),
     
     ("device_model_version", libxl_device_model_version),
     ("device_model_stubdomain", libxl_defbool),

diff --git a/tools/libxl/libxlu_cfg.c b/tools/libxl/libxlu_cfg.c
index 72815d25dddfcc6f962f437b16120e0509808300..cafc632fc1da0f468a397c87f07326722062a302 100644 (file)
--- a/tools/libxl/libxlu_cfg.c
+++ b/tools/libxl/libxlu_cfg.c
@@ -268,8 +268,9 @@ int xlu_cfg_replace_string(const XLU_Config *cfg, const char *n,
     return 0;
 }
 
-int xlu_cfg_get_long(const XLU_Config *cfg, const char *n,
-                     long *value_r, int dont_warn) {
+int xlu_cfg_get_bounded_long(const XLU_Config *cfg, const char *n,
+                             long min, long max, long *value_r,
+                             int dont_warn) {
     long l;
     XLU_ConfigSetting *set;
     int e;
@@ -303,10 +304,31 @@ int xlu_cfg_get_long(const XLU_Config *cfg, const char *n,
                     cfg->config_source, set->lineno, n);
         return EINVAL;
     }
+    if (l < min) {
+        if (!dont_warn)
+            fprintf(cfg->report,
+                    "%s:%d: warning: value `%ld' is smaller than minimum bound '%ld'\n",
+                    cfg->config_source, set->lineno, l, min);
+        return EINVAL;
+    }
+    if (l > max) {
+        if (!dont_warn)
+            fprintf(cfg->report,
+                    "%s:%d: warning: value `%ld' is greater than maximum bound '%ld'\n",
+                    cfg->config_source, set->lineno, l, max);
+        return EINVAL;
+    }
+
     *value_r= l;
     return 0;
 }
 
+int xlu_cfg_get_long(const XLU_Config *cfg, const char *n,
+                     long *value_r, int dont_warn) {
+    return xlu_cfg_get_bounded_long(cfg, n, LONG_MIN, LONG_MAX, value_r,
+                                    dont_warn);
+}
+
 int xlu_cfg_get_defbool(const XLU_Config *cfg, const char *n, libxl_defbool *b,
                      int dont_warn)
 {

diff --git a/tools/libxl/libxlutil.h b/tools/libxl/libxlutil.h
index 057cc25cb2cccc32ef0334bbfe4837b49eeb0cdb..92e35c5462786ee64acd3353dd52b4c3c1d8fd37 100644 (file)
--- a/tools/libxl/libxlutil.h
+++ b/tools/libxl/libxlutil.h
@@ -63,6 +63,8 @@ int xlu_cfg_replace_string(const XLU_Config *cfg, const char *n,
                            char **value_r, int dont_warn);
 int xlu_cfg_get_long(const XLU_Config*, const char *n, long *value_r,
                      int dont_warn);
+int xlu_cfg_get_bounded_long(const XLU_Config*, const char *n, long min,
+                             long max, long *value_r, int dont_warn);
 int xlu_cfg_get_defbool(const XLU_Config*, const char *n, libxl_defbool *b,
                      int dont_warn);
 

diff --git a/tools/python/xen/lowlevel/xc/xc.c b/tools/python/xen/lowlevel/xc/xc.c
index 44d36061413df486f0aaaca04836e423496385bd..a751e859102f479eb0a3e91d4c8f56f0657a7fb6 100644 (file)
--- a/tools/python/xen/lowlevel/xc/xc.c
+++ b/tools/python/xen/lowlevel/xc/xc.c
@@ -127,8 +127,8 @@ static PyObject *pyxc_domain_create(XcObject *self,
         },
         .max_vcpus = 1,
         .max_evtchn_port = -1, /* No limit. */
-        .max_grant_frames = 32,
-        .max_maptrack_frames = 1024,
+        .max_grant_frames = -1,
+        .max_maptrack_frames = -1,
     };
 
     static char *kwd_list[] = { "domid", "ssidref", "handle", "flags",

diff --git a/tools/xl/xl.c b/tools/xl/xl.c
index ddd29b3f1b2d591e2aef1aa883dc367587f3e2bb..3d4390a46dcb554475f7d34bcb91c671db47f2cc 100644 (file)
--- a/tools/xl/xl.c
+++ b/tools/xl/xl.c
@@ -23,6 +23,7 @@
 #include <ctype.h>
 #include <inttypes.h>
 #include <regex.h>
+#include <limits.h>
 
 #include <libxl.h>
 #include <libxl_utils.h>
@@ -96,7 +97,6 @@ static void parse_global_config(const char *configfile,
     XLU_Config *config;
     int e;
     const char *buf;
-    libxl_physinfo physinfo;
 
     config = xlu_cfg_init(stderr, configfile);
     if (!config) {
@@ -197,17 +197,19 @@ static void parse_global_config(const char *configfile,
     xlu_cfg_replace_string (config, "colo.default.proxyscript",
         &default_colo_proxy_script, 0);
 
-    if (!xlu_cfg_get_long (config, "max_grant_frames", &l, 0))
+    e = xlu_cfg_get_bounded_long (config, "max_grant_frames", 0, INT_MAX,
+                                  &l, 1);
+    if (!e)
         max_grant_frames = l;
-    else {
-        libxl_physinfo_init(&physinfo);
-        max_grant_frames = (libxl_get_physinfo(ctx, &physinfo) != 0 ||
-                            !(physinfo.max_possible_mfn >> 32))
-                           ? 32 : 64;
-        libxl_physinfo_dispose(&physinfo);
-    }
-    if (!xlu_cfg_get_long (config, "max_maptrack_frames", &l, 0))
+    else if (e != ESRCH)
+        exit(1);
+
+    e = xlu_cfg_get_bounded_long (config, "max_maptrack_frames", 0,
+                                  INT_MAX, &l, 1);
+    if (!e)
         max_maptrack_frames = l;
+    else if (e != ESRCH)
+        exit(1);
 
     libxl_cpu_bitmap_alloc(ctx, &global_vm_affinity_mask, 0);
     libxl_cpu_bitmap_alloc(ctx, &global_hvm_affinity_mask, 0);

diff --git a/tools/xl/xl_parse.c b/tools/xl/xl_parse.c
index 112f8ee026067e9319d20e6a0f9fcc19027d3e4c..b88118480485136dfa4821e0727477c6bc084942 100644 (file)
--- a/tools/xl/xl_parse.c
+++ b/tools/xl/xl_parse.c
@@ -1411,14 +1411,23 @@ void parse_config_data(const char *config_source,
         !xlu_cfg_get_string (config, "cpus_soft", &buf, 0))
         parse_vcpu_affinity(b_info, cpus, buf, num_cpus, false);
 
-    if (!xlu_cfg_get_long (config, "max_grant_frames", &l, 0))
+    e = xlu_cfg_get_bounded_long (config, "max_grant_frames", 0, INT_MAX,
+                                  &l, 1);
+    if (e == ESRCH) /* not specified */
+        b_info->max_grant_frames = max_grant_frames;
+    else if (!e)
         b_info->max_grant_frames = l;
     else
-        b_info->max_grant_frames = max_grant_frames;
-    if (!xlu_cfg_get_long (config, "max_maptrack_frames", &l, 0))
-        b_info->max_maptrack_frames = l;
-    else if (max_maptrack_frames != -1)
+        exit(1);
+
+    e = xlu_cfg_get_bounded_long (config, "max_maptrack_frames", 0,
+                                  INT_MAX, &l, 1);
+    if (e == ESRCH) /* not specified */
         b_info->max_maptrack_frames = max_maptrack_frames;
+    else if (!e)
+        b_info->max_maptrack_frames = l;
+    else
+        exit(1);
 
     libxl_defbool_set(&b_info->claim_mode, claim_mode);
 

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 51d32106b7e0a8f7c097387ade6ac2d1715268e4..3c899cd4a0842e4525812e2f8ed2313826df3356 100644 (file)
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -789,7 +789,7 @@ void __init start_xen(unsigned long boot_phys_offset,
         .flags = XEN_DOMCTL_CDF_hvm | XEN_DOMCTL_CDF_hap,
         .max_evtchn_port = -1,
         .max_grant_frames = gnttab_dom0_frames(),
-        .max_maptrack_frames = opt_max_maptrack_frames,
+        .max_maptrack_frames = -1,
     };
     int rc;
 

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 00ee87bde5c38ebb50b805ecf6b8c4618e45bfb5..7d27f360536cf846005c0dd36e28d42e8e945d0f 100644 (file)
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -697,8 +697,8 @@ void __init noreturn __start_xen(unsigned long mbi_p)
     struct xen_domctl_createdomain dom0_cfg = {
         .flags = IS_ENABLED(CONFIG_TBOOT) ? XEN_DOMCTL_CDF_s3_integrity : 0,
         .max_evtchn_port = -1,
-        .max_grant_frames = opt_max_grant_frames,
-        .max_maptrack_frames = opt_max_maptrack_frames,
+        .max_grant_frames = -1,
+        .max_maptrack_frames = -1,
     };
 
     /* Critical region without IDT or TSS.  Any fault is deadly! */

diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index b34d520f6d4939864b6546f3fe57a370178f3ecf..729f362ea87c43c1af2f7a7a631a0b0ad6fa9962 100644 (file)
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -84,11 +84,42 @@ struct grant_table {
     struct grant_table_arch arch;
 };
 
+static int parse_gnttab_limit(const char *param, const char *arg,
+                              unsigned int *valp)
+{
+    const char *e;
+    unsigned long val;
+
+    val = simple_strtoul(arg, &e, 0);
+    if ( *e )
+        return -EINVAL;
+
+    if ( val > INT_MAX )
+        return -ERANGE;
+
+    *valp = val;
+
+    return 0;
+}
+
 unsigned int __read_mostly opt_max_grant_frames = 64;
-integer_runtime_param("gnttab_max_frames", opt_max_grant_frames);
 
-unsigned int __read_mostly opt_max_maptrack_frames = 1024;
-integer_runtime_param("gnttab_max_maptrack_frames", opt_max_maptrack_frames);
+static int parse_gnttab_max_frames(const char *arg)
+{
+    return parse_gnttab_limit("gnttab_max_frames", arg,
+                              &opt_max_grant_frames);
+}
+custom_runtime_param("gnttab_max_frames", parse_gnttab_max_frames);
+
+static unsigned int __read_mostly opt_max_maptrack_frames = 1024;
+
+static int parse_gnttab_max_maptrack_frames(const char *arg)
+{
+    return parse_gnttab_limit("gnttab_max_maptrack_frames", arg,
+                              &opt_max_maptrack_frames);
+}
+custom_runtime_param("gnttab_max_maptrack_frames",
+                     parse_gnttab_max_maptrack_frames);
 
 #ifndef GNTTAB_MAX_VERSION
 #define GNTTAB_MAX_VERSION 2
@@ -1837,12 +1868,18 @@ active_alloc_failed:
     return -ENOMEM;
 }
 
-int grant_table_init(struct domain *d, unsigned int max_grant_frames,
-                     unsigned int max_maptrack_frames)
+int grant_table_init(struct domain *d, int max_grant_frames,
+                     int max_maptrack_frames)
 {
     struct grant_table *gt;
     int ret = -ENOMEM;
 
+    /* Default to maximum value if no value was specified */
+    if ( max_grant_frames < 0 )
+        max_grant_frames = opt_max_grant_frames;
+    if ( max_maptrack_frames < 0 )
+        max_maptrack_frames = opt_max_maptrack_frames;
+
     if ( max_grant_frames < INITIAL_NR_GRANT_FRAMES ||
          max_grant_frames > opt_max_grant_frames ||
          max_maptrack_frames > opt_max_maptrack_frames )

diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 9f2cfd602cb28b869d8748b5bbc2b311b6dd0d8e..e313da499f6ab9255315120afa8298d82ce8f3f5 100644 (file)
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -82,13 +82,15 @@ struct xen_domctl_createdomain {
     uint32_t iommu_opts;
 
     /*
-     * Various domain limits, which impact the quantity of resources (global
-     * mapping space, xenheap, etc) a guest may consume.
+     * Various domain limits, which impact the quantity of resources
+     * (global mapping space, xenheap, etc) a guest may consume.  For
+     * max_grant_frames and max_maptrack_frames, < 0 means "use the
+     * default maximum value in the hypervisor".
      */
     uint32_t max_vcpus;
     uint32_t max_evtchn_port;
-    uint32_t max_grant_frames;
-    uint32_t max_maptrack_frames;
+    int32_t max_grant_frames;
+    int32_t max_maptrack_frames;
 
     struct xen_arch_domainconfig arch;
 };

diff --git a/xen/include/xen/grant_table.h b/xen/include/xen/grant_table.h
index 6f9345d9ef546dbc123c73b400a1ac21dde87717..98603604b86d9a3308aadf60aca3427e6d26d6bc 100644 (file)
--- a/xen/include/xen/grant_table.h
+++ b/xen/include/xen/grant_table.h
@@ -33,11 +33,10 @@
 struct grant_table;
 
 extern unsigned int opt_max_grant_frames;
-extern unsigned int opt_max_maptrack_frames;
 
 /* Create/destroy per-domain grant table context. */
-int grant_table_init(struct domain *d, unsigned int max_grant_frames,
-                     unsigned int max_maptrack_frames);
+int grant_table_init(struct domain *d, int max_grant_frames,
+                     int max_maptrack_frames);
 void grant_table_destroy(
     struct domain *d);
 void grant_table_init_vcpu(struct vcpu *v);
@@ -65,11 +64,10 @@ int gnttab_get_status_frame(struct domain *d, unsigned long idx,
 #else
 
 #define opt_max_grant_frames 0
-#define opt_max_maptrack_frames 0
 
 static inline int grant_table_init(struct domain *d,
-                                   unsigned int max_grant_frames,
-                                   unsigned int max_maptrack_frames)
+                                   int max_grant_frames,
+                                   int max_maptrack_frames)
 {
     return 0;
 }