libxl/xl: Overhaul passthrough setting logic

LIBXL_PASSTHROUGH_UNKNOWN (aka "ENABLED" in an earlier uncommitted
version of this code) is doing double duty.  We actually need all of
the following to be specifiable:
  * "default": enable PT iff we have devices to
    pass through specified in the initial config file.
  * "enabled" (and fail if the platform doesn't support it).
  * "disabled" (and reject future PT hotplug).
  * "share_pt"/"sync_pt": enable PT and set a specific PT mode.

Defaulting and error checking should be done in libxl.  So, we make
several changes here.

We introduce "enabled", and rename "unknown" to "default".

We move all of the error checking and defaulting code from xl into
libxl.  Now, libxl__domain_config_setdefault has all of the necessary
information to get this right.  So we can do it all there.  Choosing
the specific mode is arch-specific.

We can also arrange to have only one place each which calculates
(i) whether passthrough needs to be enabled because pt devices were
specified (ii) whether pt_share can be used (for each arch).

xl now only has to parse the enum in the same way as it parses all
other enums.

This change fixes a regression from earlier 4.13-pre: until recent
changes, passthrough was only enabled by default if passthrough
devices were specified.  We restore this behaviour.

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Julien Grall <julien@xen.org>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
CC: Andrew Cooper <Andrew.Cooper3@citrix.com>
CC: Paul Durrant <pdurrant@gmail.com>
CC: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Juergen Gross <jgross@suse.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>

diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
index 64bed30bcedcfe5d5a6d13a6705df073d1fbd11e..245d3f94728a3d3574830f0855f9ff61b37390ca 100644 (file)
--- a/docs/man/xl.cfg.5.pod.in
+++ b/docs/man/xl.cfg.5.pod.in
@@ -660,6 +660,12 @@ in preference. However, the availability of this option is hardware
 specific. If B<xl info> reports B<virt_caps> containing
 B<iommu_hap_pt_share> then this option may be used.
 
+=item B<default>
+
+The default, which chooses between B<disabled> and B<enabled>
+according to whether passthrough devices are enabled in the config
+file.
+
 =back
 
 =back

diff --git a/tools/libxl/libxl_arch.h b/tools/libxl/libxl_arch.h
index d624159e53ea7d09697348b8b2de29f5d65e8f6a..ee6641b3e606e8828f9b5c60756da2f6415c3265 100644 (file)
--- a/tools/libxl/libxl_arch.h
+++ b/tools/libxl/libxl_arch.h
@@ -72,6 +72,12 @@ _hidden
 void libxl__arch_domain_build_info_setdefault(libxl__gc *gc,
                                               libxl_domain_build_info *b_info);
 
+_hidden
+int libxl__arch_passthrough_mode_setdefault(libxl__gc *gc,
+                                            uint32_t domid,
+                                            libxl_domain_config *d_config,
+                                            const libxl_physinfo *physinfo);
+
 _hidden
 int libxl__arch_extra_memory(libxl__gc *gc,
                              const libxl_domain_build_info *info,

diff --git a/tools/libxl/libxl_arm.c b/tools/libxl/libxl_arm.c
index bf31b9b3cae48ac1fb31e813d6cbf3d9935504f9..2f1ca694317954fc35f7fab4dc0fa3ef58cda565 100644 (file)
--- a/tools/libxl/libxl_arm.c
+++ b/tools/libxl/libxl_arm.c
@@ -1191,6 +1191,30 @@ void libxl__arch_domain_build_info_setdefault(libxl__gc *gc,
     libxl_domain_build_info_init_type(b_info, LIBXL_DOMAIN_TYPE_PVH);
 }
 
+int libxl__arch_passthrough_mode_setdefault(libxl__gc *gc,
+                                            uint32_t domid,
+                                            libxl_domain_config *d_config,
+                                            const libxl_physinfo *physinfo)
+{
+    int rc;
+    libxl_domain_create_info *const c_info = &d_config->c_info;
+
+    if (c_info->passthrough == LIBXL_PASSTHROUGH_ENABLED) {
+        c_info->passthrough = LIBXL_PASSTHROUGH_SHARE_PT;
+    }
+
+    if (c_info->passthrough == LIBXL_PASSTHROUGH_SYNC_PT) {
+        LOGD(ERROR, domid,
+             "passthrough=\"sync_pt\" not supported on ARM\n");
+        rc = ERROR_INVAL;
+        goto out;
+    }
+
+    rc = 0;
+ out:
+    return rc;
+}
+
 /*
  * Local variables:
  * mode: C

diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index 7869d54b320ef75dd887af91e89855a03a354ecb..d59ac2ab0556b913de42d17bbf3dbb980001ac63 100644 (file)
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -57,18 +57,6 @@ int libxl__domain_create_info_setdefault(libxl__gc *gc,
     if (!c_info->ssidref)
         c_info->ssidref = SECINITSID_DOMU;
 
-    if (info->cap_hvm_directio &&
-        (c_info->passthrough == LIBXL_PASSTHROUGH_UNKNOWN)) {
-        c_info->passthrough = ((c_info->type == LIBXL_DOMAIN_TYPE_PV) ||
-                               !info->cap_iommu_hap_pt_share) ?
-            LIBXL_PASSTHROUGH_SYNC_PT : LIBXL_PASSTHROUGH_SHARE_PT;
-    } else if (!info->cap_hvm_directio) {
-        c_info->passthrough = LIBXL_PASSTHROUGH_DISABLED;
-    }
-
-    /* An explicit setting should now have been chosen */
-    assert(c_info->passthrough != LIBXL_PASSTHROUGH_UNKNOWN);
-
     return 0;
 }
 
@@ -591,7 +579,7 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
                 libxl_defbool_val(info->oos) ? 0 : XEN_DOMCTL_CDF_oos_off;
         }
 
-        assert(info->passthrough != LIBXL_PASSTHROUGH_UNKNOWN);
+        assert(info->passthrough != LIBXL_PASSTHROUGH_DEFAULT);
         LOG(DETAIL, "passthrough: %s",
             libxl_passthrough_to_string(info->passthrough));
 
@@ -908,6 +896,7 @@ int libxl__domain_config_setdefault(libxl__gc *gc,
     libxl_ctx *ctx = libxl__gc_owner(gc);
     int ret;
     bool pod_enabled = false;
+    libxl_domain_create_info *c_info = &d_config->c_info;
 
     libxl_physinfo physinfo;
     ret = libxl_get_physinfo(CTX, &physinfo);
@@ -979,6 +968,34 @@ int libxl__domain_config_setdefault(libxl__gc *gc,
         goto error_out;
     }
 
+    bool need_pt = d_config->num_pcidevs || d_config->num_dtdevs;
+    if (c_info->passthrough == LIBXL_PASSTHROUGH_DEFAULT) {
+        c_info->passthrough = need_pt
+            ? LIBXL_PASSTHROUGH_ENABLED : LIBXL_PASSTHROUGH_DISABLED;
+    }
+
+    bool iommu_enabled = physinfo.cap_hvm_directio;
+    if (c_info->passthrough != LIBXL_PASSTHROUGH_DISABLED && !iommu_enabled) {
+        LOGD(ERROR, domid,
+             "passthrough not supported on this platform\n");
+        ret = ERROR_INVAL;
+        goto error_out;
+    }
+
+    if (c_info->passthrough == LIBXL_PASSTHROUGH_DISABLED && need_pt) {
+        LOGD(ERROR, domid,
+             "passthrough disabled but devices are specified");
+        ret = ERROR_INVAL;
+        goto error_out;
+    }
+
+    ret = libxl__arch_passthrough_mode_setdefault(gc,domid,d_config,&physinfo);
+    if (ret) goto error_out;
+
+    /* An explicit setting should now have been chosen */
+    assert(c_info->passthrough != LIBXL_PASSTHROUGH_DEFAULT);
+    assert(c_info->passthrough != LIBXL_PASSTHROUGH_ENABLED);
+
     /* If target_memkb is smaller than max_memkb, the subsequent call
      * to libxc when building HVM domain will enable PoD mode.
      */

diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 3ac9494b8033971cbdb21f54003606439cf38915..0546d7865ab85cd1778f9a78622affe5192a9f14 100644 (file)
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -264,10 +264,11 @@ libxl_vkb_backend = Enumeration("vkb_backend", [
     ])
 
 libxl_passthrough = Enumeration("passthrough", [
-    (0, "unknown"),
+    (0, "default"),
     (1, "disabled"),
-    (2, "sync_pt"),
-    (3, "share_pt"),
+    (2, "enabled"), # becomes {sync,share}_pt once defaults are evaluated
+    (3, "sync_pt"),
+    (4, "share_pt"),
     ])
 
 #

diff --git a/tools/libxl/libxl_x86.c b/tools/libxl/libxl_x86.c
index c0f88a7eaa4622320f28458be3795f5432734e51..8b804537bafe003ef247b13f1c593846dbafbf12 100644 (file)
--- a/tools/libxl/libxl_x86.c
+++ b/tools/libxl/libxl_x86.c
@@ -631,6 +631,47 @@ void libxl__arch_domain_build_info_setdefault(libxl__gc *gc,
     libxl_defbool_setdefault(&b_info->acpi, true);
 }
 
+int libxl__arch_passthrough_mode_setdefault(libxl__gc *gc,
+                                            uint32_t domid,
+                                            libxl_domain_config *d_config,
+                                            const libxl_physinfo *physinfo)
+{
+    int rc;
+    libxl_domain_create_info *const c_info = &d_config->c_info;
+
+    if (c_info->passthrough != LIBXL_PASSTHROUGH_DISABLED &&
+        c_info->type == LIBXL_DOMAIN_TYPE_PVH) {
+        LOGD(ERROR, domid,
+             "passthrough not yet supported for x86 PVH guests\n");
+        rc = ERROR_INVAL;
+        goto out;
+    }
+
+    const char *whynot_pt_share =
+        c_info->type == LIBXL_DOMAIN_TYPE_PV ? "not valid for PV domain" :
+        !physinfo->cap_iommu_hap_pt_share ? "not supported on this platform" :
+        !libxl_defbool_val(d_config->c_info.hap) ?"only valid for HAP guests":
+        NULL;
+
+    if (c_info->passthrough == LIBXL_PASSTHROUGH_ENABLED) {
+        c_info->passthrough = whynot_pt_share
+            ? LIBXL_PASSTHROUGH_SYNC_PT : LIBXL_PASSTHROUGH_SHARE_PT;
+    }
+
+    if (c_info->passthrough == LIBXL_PASSTHROUGH_SHARE_PT && whynot_pt_share) {
+        LOGD(ERROR, domid,
+             "passthrough=\"share_pt\" %s\n",
+             whynot_pt_share);
+        rc = ERROR_INVAL;
+        goto out;
+    }
+
+    rc = 0;
+ out:
+    return rc;
+}
+
+
 /*
  * Local variables:
  * mode: C

diff --git a/tools/xl/xl_parse.c b/tools/xl/xl_parse.c
index 79871c22d09a108ab1962caf9e8a9b2062ac30a0..112f8ee026067e9319d20e6a0f9fcc19027d3e4c 100644 (file)
--- a/tools/xl/xl_parse.c
+++ b/tools/xl/xl_parse.c
@@ -1222,7 +1222,6 @@ void parse_config_data(const char *config_source,
     int pci_seize = 0;
     int i, e;
     char *kernel_basename;
-    bool iommu_enabled, iommu_hap_pt_share;
 
     libxl_domain_create_info *c_info = &d_config->c_info;
     libxl_domain_build_info *b_info = &d_config->b_info;
@@ -1234,8 +1233,6 @@ void parse_config_data(const char *config_source,
         exit(EXIT_FAILURE);
     }
 
-    iommu_enabled = physinfo.cap_hvm_directio;
-    iommu_hap_pt_share = physinfo.cap_iommu_hap_pt_share;
     libxl_physinfo_dispose(&physinfo);
 
     config= xlu_cfg_init(stderr, config_source);
@@ -1509,67 +1506,13 @@ void parse_config_data(const char *config_source,
         }
     }
 
-    if (xlu_cfg_get_string(config, "passthrough", &buf, 0)) {
-        c_info->passthrough =
-            (d_config->num_pcidevs || d_config->num_dtdevs)
-            ? LIBXL_PASSTHROUGH_UNKNOWN : LIBXL_PASSTHROUGH_DISABLED;
-    } else {
-        if (!strcasecmp("enabled", buf))
-            c_info->passthrough = LIBXL_PASSTHROUGH_UNKNOWN;
-        else {
-            libxl_passthrough o;
-
-            e = libxl_passthrough_from_string(buf, &o);
-            if (e || !strcasecmp("unknown", buf)) {
-                fprintf(stderr,
-                        "ERROR: unknown passthrough option '%s'\n",
-                        buf);
-                exit(-ERROR_FAIL);
-            }
-
-            c_info->passthrough = o;
-        }
-    }
-
-    switch (c_info->passthrough) {
-    case LIBXL_PASSTHROUGH_UNKNOWN:
-        /*
-         * Choose a suitable default. libxl would also do this but
-         * choosing here allows the code calculating 'iommu_memkb'
-         * below make an informed decision.
-         */
-        c_info->passthrough =
-            (c_info->type == LIBXL_DOMAIN_TYPE_PV) || !iommu_hap_pt_share
-            ? LIBXL_PASSTHROUGH_SYNC_PT : LIBXL_PASSTHROUGH_SHARE_PT;
-        break;
-
-    case LIBXL_PASSTHROUGH_DISABLED:
-        if (d_config->num_pcidevs || d_config->num_dtdevs) {
+    if (!xlu_cfg_get_string(config, "passthrough", &buf, 0)) {
+        if (libxl_passthrough_from_string(buf, &c_info->passthrough)) {
             fprintf(stderr,
-                    "ERROR: passthrough disabled but devices are specified\n");
-            exit(-ERROR_FAIL);
-        }
-        break;
-    case LIBXL_PASSTHROUGH_SHARE_PT:
-        if (c_info->type == LIBXL_DOMAIN_TYPE_PV) {
-            fprintf(stderr,
-                    "ERROR: passthrough=\"share_pt\" not valid for PV domain\n");
-            exit(-ERROR_FAIL);
-        } else if (!iommu_hap_pt_share) {
-            fprintf(stderr,
-                    "ERROR: passthrough=\"share_pt\" not supported on this platform\n");
-            exit(-ERROR_FAIL);
+                    "ERROR: unknown passthrough option '%s'\n",
+                    buf);
+            exit(1);
         }
-        break;
-    case LIBXL_PASSTHROUGH_SYNC_PT:
-        break;
-    }
-
-    if ((c_info->passthrough != LIBXL_PASSTHROUGH_DISABLED) &&
-        !iommu_enabled) {
-        fprintf(stderr,
-                "ERROR: passthrough not supported on this platform\n");
-        exit(-ERROR_FAIL);
     }
 
     if (!xlu_cfg_get_long(config, "shadow_memory", &l, 0))