[RFC,v2,1/8] domain: GADDR based shared guest area registration alternative - teardown

Commit Message

Jan Beulich Jan. 23, 2023, 2:53 p.m. UTC

In preparation of the introduction of new vCPU operations allowing to
register the respective areas (one of the two is x86-specific) by
guest-physical address, add the necessary domain cleanup hooks.

Signed-off-by: Jan Beulich <[e-mail]>
Reviewed-by: Julien Grall <[e-mail]>
---
RFC: Zapping the areas in pv_shim_shutdown() may not be strictly
     necessary: Aiui unmap_vcpu_info() is called only because the vCPU
     info area cannot be re-registered. Beyond that I guess the
     assumption is that the areas would only be re-registered as they
     were before. If that's not the case I wonder whether the guest
     handles for both areas shouldn't also be zapped.
---
v2: Add assertion in unmap_guest_area().

Patch

--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1014,7 +1014,10 @@  int arch_domain_soft_reset(struct domain
     }
 
     for_each_vcpu ( d, v )
+    {
         set_xen_guest_handle(v->arch.time_info_guest, NULL);
+        unmap_guest_area(v, &v->arch.time_guest_area);
+    }
 
  exit_put_gfn:
     put_gfn(d, gfn_x(gfn));
@@ -2329,6 +2332,8 @@  int domain_relinquish_resources(struct d
             if ( ret )
                 return ret;
 
+            unmap_guest_area(v, &v->arch.time_guest_area);
+
             vpmu_destroy(v);
         }
 
--- a/xen/arch/x86/include/asm/domain.h
+++ b/xen/arch/x86/include/asm/domain.h
@@ -658,6 +658,7 @@  struct arch_vcpu
 
     /* A secondary copy of the vcpu time info. */
     XEN_GUEST_HANDLE(vcpu_time_info_t) time_info_guest;
+    struct guest_area time_guest_area;
 
     struct arch_vm_event *vm_event;
 
--- a/xen/arch/x86/pv/shim.c
+++ b/xen/arch/x86/pv/shim.c
@@ -394,8 +394,10 @@  int pv_shim_shutdown(uint8_t reason)
 
     for_each_vcpu ( d, v )
     {
-        /* Unmap guest vcpu_info pages. */
+        /* Unmap guest vcpu_info page and runstate/time areas. */
         unmap_vcpu_info(v);
+        unmap_guest_area(v, &v->runstate_guest_area);
+        unmap_guest_area(v, &v->arch.time_guest_area);
 
         /* Reset the periodic timer to the default value. */
         vcpu_set_periodic_timer(v, MILLISECS(10));
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -963,7 +963,10 @@  int domain_kill(struct domain *d)
         if ( cpupool_move_domain(d, cpupool0) )
             return -ERESTART;
         for_each_vcpu ( d, v )
+        {
             unmap_vcpu_info(v);
+            unmap_guest_area(v, &v->runstate_guest_area);
+        }
         d->is_dying = DOMDYING_dead;
         /* Mem event cleanup has to go here because the rings 
          * have to be put before we call put_domain. */
@@ -1417,6 +1420,7 @@  int domain_soft_reset(struct domain *d,
     {
         set_xen_guest_handle(runstate_guest(v), NULL);
         unmap_vcpu_info(v);
+        unmap_guest_area(v, &v->runstate_guest_area);
     }
 
     rc = arch_domain_soft_reset(d);
@@ -1568,6 +1572,19 @@  void unmap_vcpu_info(struct vcpu *v)
     put_page_and_type(mfn_to_page(mfn));
 }
 
+/*
+ * This is only intended to be used for domain cleanup (or more generally only
+ * with at least the respective vCPU, if it's not the current one, reliably
+ * paused).
+ */
+void unmap_guest_area(struct vcpu *v, struct guest_area *area)
+{
+    struct domain *d = v->domain;
+
+    if ( v != current )
+        ASSERT(atomic_read(&v->pause_count) | atomic_read(&d->pause_count));
+}
+
 int default_initialise_vcpu(struct vcpu *v, XEN_GUEST_HANDLE_PARAM(void) arg)
 {
     struct vcpu_guest_context *ctxt;
--- a/xen/include/xen/domain.h
+++ b/xen/include/xen/domain.h
@@ -5,6 +5,12 @@ 
 #include <xen/types.h>
 
 #include <public/xen.h>
+
+struct guest_area {
+    struct page_info *pg;
+    void *map;
+};
+
 #include <asm/domain.h>
 #include <asm/numa.h>
 
@@ -76,6 +82,11 @@  void arch_vcpu_destroy(struct vcpu *v);
 int map_vcpu_info(struct vcpu *v, unsigned long gfn, unsigned int offset);
 void unmap_vcpu_info(struct vcpu *v);
 
+int map_guest_area(struct vcpu *v, paddr_t gaddr, unsigned int size,
+                   struct guest_area *area,
+                   void (*populate)(void *dst, struct vcpu *v));
+void unmap_guest_area(struct vcpu *v, struct guest_area *area);
+
 int arch_domain_create(struct domain *d,
                        struct xen_domctl_createdomain *config,
                        unsigned int flags);
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -202,6 +202,7 @@  struct vcpu
         XEN_GUEST_HANDLE(vcpu_runstate_info_compat_t) compat;
     } runstate_guest; /* guest address */
 #endif
+    struct guest_area runstate_guest_area;
     unsigned int     new_state;
 
     /* Has the FPU been initialised? */