Add a new domctl to get a single record from the HVM save context

Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>

xen/arch/x86/domctl.c

@@ -417,6 +417,34 @@ long arch_do_domctl(
     }
     break;
 
+    case XEN_DOMCTL_gethvmcontext_partial:
+    { 
+        struct domain *d;
+
+        ret = -ESRCH;
+        if ( (d = rcu_lock_domain_by_id(domctl->domain)) == NULL )
+            break;
+
+        ret = xsm_hvmcontext(d, domctl->cmd);
+        if ( ret )
+            goto gethvmcontext_partial_out;
+
+        ret = -EINVAL;
+        if ( !is_hvm_domain(d) ) 
+            goto gethvmcontext_partial_out;
+
+        domain_pause(d);
+        ret = hvm_save_one(d, domctl->u.hvmcontext_partial.type,
+                           domctl->u.hvmcontext_partial.instance,
+                           domctl->u.hvmcontext_partial.buffer);
+        domain_unpause(d);
+
+    gethvmcontext_partial_out:
+        rcu_unlock_domain(d);
+    }
+    break;
+
+
     case XEN_DOMCTL_set_address_size:
     {
         struct domain *d;

xen/common/hvm/save.c

@@ -26,6 +26,7 @@
 #include <xen/version.h>
 #include <public/version.h>
 #include <xen/sched.h>
+#include <xen/guest_access.h>
 
 #include <asm/hvm/support.h>
 
@@ -75,6 +76,53 @@ size_t hvm_save_size(struct domain *d)
     return sz;
 }
 
+/* Extract a single instance of a save record, by marshalling all
+ * records of that type and copying out the one we need. */
+int hvm_save_one(struct domain *d, uint16_t typecode, uint16_t instance, 
+                 XEN_GUEST_HANDLE_64(uint8) handle)
+{
+    int rv = 0;
+    size_t sz = 0;
+    struct vcpu *v;
+    hvm_domain_context_t ctxt = { 0, };
+
+    if ( d->is_dying 
+         || typecode > HVM_SAVE_CODE_MAX 
+         || hvm_sr_handlers[typecode].size < sizeof(struct hvm_save_descriptor)
+         || hvm_sr_handlers[typecode].save == NULL )
+        return -EINVAL;
+
+    if ( hvm_sr_handlers[typecode].kind == HVMSR_PER_VCPU )
+        for_each_vcpu(d, v)
+            sz += hvm_sr_handlers[typecode].size;
+    else 
+        sz = hvm_sr_handlers[typecode].size;
+    
+    if ( (instance + 1) * hvm_sr_handlers[typecode].size > sz )
+        return -EINVAL;
+
+    ctxt.size = sz;
+    ctxt.data = xmalloc_bytes(sz);
+    if ( !ctxt.data )
+        return -ENOMEM;
+
+    if ( hvm_sr_handlers[typecode].save(d, &ctxt) != 0 )
+    {
+        gdprintk(XENLOG_ERR, 
+                 "HVM save: failed to save type %"PRIu16"\n", typecode);
+        rv = -EFAULT;
+    }
+    else if ( copy_to_guest(handle,
+                            ctxt.data 
+                            + (instance * hvm_sr_handlers[typecode].size) 
+                            + sizeof (struct hvm_save_descriptor), 
+                            hvm_sr_handlers[typecode].size
+                            - sizeof (struct hvm_save_descriptor)) )
+        rv = -EFAULT;
+
+    xfree(ctxt.data);
+    return rv;
+}
 
 int hvm_save(struct domain *d, hvm_domain_context_t *h)
 {

xen/include/public/domctl.h

@@ -630,6 +630,17 @@ struct xen_domctl_debug_op {
 typedef struct xen_domctl_debug_op xen_domctl_debug_op_t;
 DEFINE_XEN_GUEST_HANDLE(xen_domctl_debug_op_t);
 
+/*
+ * Request a particular record from the HVM context
+ */
+#define XEN_DOMCTL_gethvmcontext_partial   55
+typedef struct xen_domctl_hvmcontext_partial {
+    uint32_t type;                      /* IN: Type of record required */
+    uint32_t instance;                  /* IN: Instance of that type */
+    XEN_GUEST_HANDLE_64(uint8) buffer;  /* OUT: buffer to write record into */
+} xen_domctl_hvmcontext_partial_t;
+DEFINE_XEN_GUEST_HANDLE(xen_domctl_hvmcontext_partial_t);
+
 
 struct xen_domctl {
     uint32_t cmd;
@@ -658,6 +669,7 @@ struct xen_domctl {
         struct xen_domctl_settimeoffset     settimeoffset;
         struct xen_domctl_real_mode_area    real_mode_area;
         struct xen_domctl_hvmcontext        hvmcontext;
+        struct xen_domctl_hvmcontext_partial hvmcontext_partial;
         struct xen_domctl_address_size      address_size;
         struct xen_domctl_sendtrigger       sendtrigger;
         struct xen_domctl_get_device_group  get_device_group;

xen/include/xen/hvm/save.h

@@ -152,6 +152,8 @@ __initcall(__hvm_register_##_x##_save_and_restore);
 /* Entry points for saving and restoring HVM domain state */
 size_t hvm_save_size(struct domain *d);
 int hvm_save(struct domain *d, hvm_domain_context_t *h);
+int hvm_save_one(struct domain *d,  uint16_t typecode, uint16_t instance, 
+                 XEN_GUEST_HANDLE_64(uint8) handle);
 int hvm_load(struct domain *d, hvm_domain_context_t *h);
 
 /* Arch-specific definitions. */

xen/xsm/flask/hooks.c

@@ -820,6 +820,7 @@ static int flask_hvmcontext(struct domain *d, uint32_t cmd)
             perm = HVM__SETHVMC;
         break;
         case XEN_DOMCTL_gethvmcontext:
+        case XEN_DOMCTL_gethvmcontext_partial:
             perm = HVM__GETHVMC;
         break;
         default: