[Xen-devel] [PATCH 6/6] xen/public: Obsolete HVM_PARAM_PAE_ENABLED

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

HVM_PARAM_PAE_ENABLED is undocumented and Xen has never acted upon its value,
contrary perhaps to expectations based on how other boolean fields work.

It was only ever used as a non-standard calling convention for
xc_cpuid_apply_policy() but that has been fixed now.

Purge its use, and any possible confusion over its behaviour, by having Xen
reject any attempts to use it.  Forgo setting it up in libxl's
hvm_set_conf_params().  The only backwards compatibility necessary is to have
the HVM restore stream discard it if found.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien@xxxxxxx>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
 tools/libxc/xc_sr_restore_x86_hvm.c | 10 ++++++++++
 tools/libxc/xc_sr_save_x86_hvm.c    |  1 -
 tools/libxl/libxl_x86.c             |  8 +-------
 xen/arch/arm/hvm.c                  |  3 ++-
 xen/arch/x86/hvm/hvm.c              |  2 ++
 xen/include/public/hvm/params.h     |  2 +-
 6 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/tools/libxc/xc_sr_restore_x86_hvm.c 
b/tools/libxc/xc_sr_restore_x86_hvm.c
index 3f78248f32..da1574ce11 100644
--- a/tools/libxc/xc_sr_restore_x86_hvm.c
+++ b/tools/libxc/xc_sr_restore_x86_hvm.c
@@ -72,6 +72,16 @@ static int handle_hvm_params(struct xc_sr_context *ctx,
         case HVM_PARAM_BUFIOREQ_PFN:
             xc_clear_domain_page(xch, ctx->domid, entry->value);
             break;
+
+        case HVM_PARAM_PAE_ENABLED:
+            /*
+             * This HVM_PARAM only ever existed a non-standard calling ABI for
+             * xc_cpuid_apply_policy().  It has now been updated to use a
+             * regular calling convention, making the param obsolete.
+             *
+             * Discard if we find it in an old migration stream.
+             */
+            continue;
         }
 
         rc = xc_hvm_param_set(xch, ctx->domid, entry->index, entry->value);
diff --git a/tools/libxc/xc_sr_save_x86_hvm.c b/tools/libxc/xc_sr_save_x86_hvm.c
index d99efe65e5..7d3f3ddb8f 100644
--- a/tools/libxc/xc_sr_save_x86_hvm.c
+++ b/tools/libxc/xc_sr_save_x86_hvm.c
@@ -71,7 +71,6 @@ static int write_hvm_params(struct xc_sr_context *ctx)
         HVM_PARAM_ACPI_IOPORTS_LOCATION,
         HVM_PARAM_VIRIDIAN,
         HVM_PARAM_IDENT_PT,
-        HVM_PARAM_PAE_ENABLED,
         HVM_PARAM_VM_GENERATION_ID_ADDR,
         HVM_PARAM_IOREQ_SERVER_PFN,
         HVM_PARAM_NR_IOREQ_SERVER_PAGES,
diff --git a/tools/libxl/libxl_x86.c b/tools/libxl/libxl_x86.c
index 1cae0e2b26..f8bc828e62 100644
--- a/tools/libxl/libxl_x86.c
+++ b/tools/libxl/libxl_x86.c
@@ -391,12 +391,10 @@ static int hvm_set_conf_params(libxl__gc *gc, uint32_t 
domid,
     libxl_ctx *ctx = libxl__gc_owner(gc);
     xc_interface *xch = ctx->xch;
     int ret = ERROR_FAIL;
-    bool pae = true, altp2m = info->altp2m;
+    bool altp2m = info->altp2m;
 
     switch(info->type) {
     case LIBXL_DOMAIN_TYPE_HVM:
-        pae = libxl_defbool_val(info->u.hvm.pae);
-
         /* The config parameter "altp2m" replaces the parameter "altp2mhvm". 
For
          * legacy reasons, both parameters are accepted on x86 HVM guests.
          *
@@ -425,10 +423,6 @@ static int hvm_set_conf_params(libxl__gc *gc, uint32_t 
domid,
 
         /* Fallthrough */
     case LIBXL_DOMAIN_TYPE_PVH:
-        if (xc_hvm_param_set(xch, domid, HVM_PARAM_PAE_ENABLED, pae)) {
-            LOG(ERROR, "Couldn't set HVM_PARAM_PAE_ENABLED");
-            goto out;
-        }
         if (xc_hvm_param_set(xch, domid, HVM_PARAM_TIMER_MODE,
                              timer_mode(info))) {
             LOG(ERROR, "Couldn't set HVM_PARAM_TIMER_MODE");
diff --git a/xen/arch/arm/hvm.c b/xen/arch/arm/hvm.c
index 76b27c9168..f3426f37fe 100644
--- a/xen/arch/arm/hvm.c
+++ b/xen/arch/arm/hvm.c
@@ -46,7 +46,8 @@ long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE_PARAM(void) 
arg)
         if ( copy_from_guest(&a, arg, 1) )
             return -EFAULT;
 
-        if ( a.index >= HVM_NR_PARAMS )
+        if ( a.index >= HVM_NR_PARAMS ||
+             a.index == HVM_PARAM_PAE_ENABLED )
             return -EINVAL;
 
         d = rcu_lock_domain_by_any_id(a.domid);
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 00a9e70b7c..2b869ac997 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4104,6 +4104,7 @@ static int hvm_allow_set_param(struct domain *d,
     case HVM_PARAM_X87_FIP_WIDTH:
         break;
     /* The following parameters are deprecated. */
+    case HVM_PARAM_PAE_ENABLED:
     case HVM_PARAM_DM_DOMAIN:
     case HVM_PARAM_BUFIOREQ_EVTCHN:
         rc = -EPERM;
@@ -4410,6 +4411,7 @@ static int hvm_allow_get_param(struct domain *d,
     case HVM_PARAM_X87_FIP_WIDTH:
         break;
     /* The following parameters are deprecated. */
+    case HVM_PARAM_PAE_ENABLED:
     case HVM_PARAM_DM_DOMAIN:
     case HVM_PARAM_BUFIOREQ_EVTCHN:
         rc = -ENODATA;
diff --git a/xen/include/public/hvm/params.h b/xen/include/public/hvm/params.h
index 36832e4b94..faa6bda095 100644
--- a/xen/include/public/hvm/params.h
+++ b/xen/include/public/hvm/params.h
@@ -86,7 +86,7 @@
 #define HVM_PARAM_STORE_PFN    1
 #define HVM_PARAM_STORE_EVTCHN 2
 
-#define HVM_PARAM_PAE_ENABLED  4
+#define HVM_PARAM_PAE_ENABLED  4 /* Obsolete.  Do not use. */
 
 #define HVM_PARAM_IOREQ_PFN    5
 
-- 
2.11.0


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