xen/arm, libxl: Revert XEN_DOMCTL_shadow_op; use p2m mempool hypercalls

This reverts most of commit cf2a68d2ff, and bits
of cbea5a1149.

First of all, with ARM borrowing x86's implementation, the logic to set the
pool size should have been common, not duplicated.  Introduce
libxl__domain_set_paging_mempool_size() as a shared implementation, and use it
from the ARM and x86 paths.  It is left as an exercise to the reader to judge
how libxl/xl can reasonably function without the ability to query the pool
size...

Remove ARM's p2m_domctl() infrastructure now the functioanlity has been
replaced with a working and unit tested interface.

This is part of XSA-409 / CVE-2022-33747.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>

tools/libs/light/libxl_arm.c

@@ -209,19 +209,7 @@ int libxl__arch_domain_create(libxl__gc *gc,
                               libxl__domain_build_state *state,
                               uint32_t domid)
 {
-    libxl_ctx *ctx = libxl__gc_owner(gc);
-    unsigned int shadow_mb = DIV_ROUNDUP(d_config->b_info.shadow_memkb, 1024);
-
-    int r = xc_shadow_control(ctx->xch, domid,
-                              XEN_DOMCTL_SHADOW_OP_SET_ALLOCATION,
-                              &shadow_mb, 0);
-    if (r) {
-        LOGED(ERROR, domid,
-              "Failed to set %u MiB shadow allocation", shadow_mb);
-        return ERROR_FAIL;
-    }
-
-    return 0;
+    return libxl__domain_set_paging_mempool_size(gc, d_config, domid);
 }
 
 int libxl__arch_extra_memory(libxl__gc *gc,

tools/libs/light/libxl_dom.c

@@ -1448,6 +1448,24 @@ out:
     return rc;
 }
 
+int libxl__domain_set_paging_mempool_size(
+    libxl__gc *gc, libxl_domain_config *d_config, uint32_t domid)
+{
+    uint64_t shadow_mem;
+
+    shadow_mem = d_config->b_info.shadow_memkb;
+    shadow_mem <<= 10;
+
+    int r = xc_set_paging_mempool_size(CTX->xch, domid, shadow_mem);
+    if (r) {
+        LOGED(ERROR, domid,
+              "Failed to set paging mempool size to %"PRIu64"kB", shadow_mem);
+        return ERROR_FAIL;
+    }
+
+    return 0;
+}
+
 /*
  * Local variables:
  * mode: C

tools/libs/light/libxl_internal.h

@@ -4864,6 +4864,9 @@ int libxl__is_domid_recent(libxl__gc *gc, uint32_t domid, bool *recent);
 /* os-specific implementation of setresuid() */
 int libxl__setresuid(uid_t ruid, uid_t euid, uid_t suid);
 
+_hidden int libxl__domain_set_paging_mempool_size(
+    libxl__gc *gc, libxl_domain_config *d_config, uint32_t domid);
+
 #endif
 
 /*

tools/libs/light/libxl_x86.c

@@ -529,20 +529,9 @@ int libxl__arch_domain_create(libxl__gc *gc,
         xc_domain_set_time_offset(ctx->xch, domid, rtc_timeoffset);
 
     if (d_config->b_info.type != LIBXL_DOMAIN_TYPE_PV) {
-        unsigned int shadow_mb = DIV_ROUNDUP(d_config->b_info.shadow_memkb,
-                                             1024);
-        int r = xc_shadow_control(ctx->xch, domid,
-                                  XEN_DOMCTL_SHADOW_OP_SET_ALLOCATION,
-                                  &shadow_mb, 0);
-
-        if (r) {
-            LOGED(ERROR, domid,
-                  "Failed to set %u MiB %s allocation",
-                  shadow_mb,
-                  libxl_defbool_val(d_config->c_info.hap) ? "HAP" : "shadow");
-            ret = ERROR_FAIL;
+        ret = libxl__domain_set_paging_mempool_size(gc, d_config, domid);
+        if (ret)
             goto out;
-        }
     }
 
     if (d_config->c_info.type == LIBXL_DOMAIN_TYPE_PV &&

xen/arch/arm/domctl.c

@@ -47,64 +47,11 @@ static int handle_vuart_init(struct domain *d,
     return rc;
 }
 
-static long p2m_domctl(struct domain *d, struct xen_domctl_shadow_op *sc,
-                       XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
-{
-    long rc;
-    bool preempted = false;
-
-    if ( unlikely(d == current->domain) )
-    {
-        printk(XENLOG_ERR "Tried to do a p2m domctl op on itself.\n");
-        return -EINVAL;
-    }
-
-    if ( unlikely(d->is_dying) )
-    {
-        printk(XENLOG_ERR "Tried to do a p2m domctl op on dying domain %u\n",
-               d->domain_id);
-        return -EINVAL;
-    }
-
-    switch ( sc->op )
-    {
-    case XEN_DOMCTL_SHADOW_OP_SET_ALLOCATION:
-    {
-        /* Allow and handle preemption */
-        spin_lock(&d->arch.paging.lock);
-        rc = p2m_set_allocation(d, sc->mb << (20 - PAGE_SHIFT), &preempted);
-        spin_unlock(&d->arch.paging.lock);
-
-        if ( preempted )
-            /* Not finished. Set up to re-run the call. */
-            rc = hypercall_create_continuation(__HYPERVISOR_domctl, "h",
-                                               u_domctl);
-        else
-            /* Finished. Return the new allocation. */
-            sc->mb = p2m_get_allocation(d);
-
-        return rc;
-    }
-    case XEN_DOMCTL_SHADOW_OP_GET_ALLOCATION:
-    {
-        sc->mb = p2m_get_allocation(d);
-        return 0;
-    }
-    default:
-    {
-        printk(XENLOG_ERR "Bad p2m domctl op %u\n", sc->op);
-        return -EINVAL;
-    }
-    }
-}
-
 long arch_do_domctl(struct xen_domctl *domctl, struct domain *d,
                     XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
 {
     switch ( domctl->cmd )
     {
-    case XEN_DOMCTL_shadow_op:
-        return p2m_domctl(d, &domctl->u.shadow_op, u_domctl);
     case XEN_DOMCTL_cacheflush:
     {
         gfn_t s = _gfn(domctl->u.cacheflush.start_pfn);

xen/arch/arm/include/asm/p2m.h

@@ -222,7 +222,6 @@ void p2m_restore_state(struct vcpu *n);
 /* Print debugging/statistial info about a domain's p2m */
 void p2m_dump_info(struct domain *d);
 
-unsigned int p2m_get_allocation(struct domain *d);
 int p2m_set_allocation(struct domain *d, unsigned long pages, bool *preempted);
 int p2m_teardown_allocation(struct domain *d);
 

xen/arch/arm/p2m.c

@@ -92,14 +92,6 @@ static void p2m_free_page(struct domain *d, struct page_info *pg)
     spin_unlock(&d->arch.paging.lock);
 }
 
-/* Return the size of the pool, rounded up to the nearest MB */
-unsigned int p2m_get_allocation(struct domain *d)
-{
-    unsigned long nr_pages = ACCESS_ONCE(d->arch.paging.p2m_total_pages);
-
-    return ROUNDUP(nr_pages, 1 << (20 - PAGE_SHIFT)) >> (20 - PAGE_SHIFT);
-}
-
 /* Return the size of the pool, in bytes. */
 int arch_get_paging_mempool_size(struct domain *d, uint64_t *size)
 {