[PATCH v3] x86/altp2m: Add a subop for obtaining the mem access of a page

* [PATCH v3] x86/altp2m: Add a subop for obtaining the mem access of a page
@ 2018-07-25 11:16 Adrian Pop
  2018-07-31 11:37 ` Jan Beulich
  0 siblings, 1 reply; 5+ messages in thread
From: Adrian Pop @ 2018-07-25 11:16 UTC (permalink / raw)
  To: xen-devel
  Cc: Stefano Stabellini, Wei Liu, Razvan Cojocaru, George Dunlap,
	Andrew Cooper, Adrian Pop, Ian Jackson, Tim Deegan, Julien Grall,
	Tamas K Lengyel, Jan Beulich, Sergej Proskurin

Currently there is a subop for setting the memaccess of a page, but not
for consulting it.  The new HVMOP_altp2m_get_mem_access adds this
functionality.

Both altp2m get/set mem access functions use the struct
xen_hvm_altp2m_mem_access which has now dropped the `set' part and has
been renamed from xen_hvm_altp2m_set_mem_access.

Signed-off-by: Adrian Pop <apop@bitdefender.com>
---
Changes in v3:
- remove the unrelated helper function
- simplify the locking in p2m_get_mem_access

Changes in v2:
- use the _p2m_get_mem_access helper from p2m_get_mem_access
- minor Arm adjustments
- move out the addition of a memaccess helper function to a separate
  patch in the attempts of making the diff clearer
---
 tools/libxc/include/xenctrl.h   |  3 +++
 tools/libxc/xc_altp2m.c         | 33 ++++++++++++++++++++++++++++++---
 xen/arch/arm/mem_access.c       |  8 ++++++--
 xen/arch/x86/hvm/hvm.c          | 26 ++++++++++++++++++++++----
 xen/arch/x86/mm/mem_access.c    | 21 +++++++++++++++++++--
 xen/common/mem_access.c         |  2 +-
 xen/include/public/hvm/hvm_op.h | 10 ++++++----
 xen/include/xen/mem_access.h    |  3 ++-
 8 files changed, 89 insertions(+), 17 deletions(-)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index dd7d8a9724..82286c2f52 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -1972,6 +1972,9 @@ int xc_altp2m_set_mem_access(xc_interface *handle, uint32_t domid,
 int xc_altp2m_set_mem_access_multi(xc_interface *handle, uint32_t domid,
                                    uint16_t view_id, uint8_t *access,
                                    uint64_t *gfns, uint32_t nr);
+int xc_altp2m_get_mem_access(xc_interface *handle, uint32_t domid,
+                             uint16_t view_id, xen_pfn_t gfn,
+                             xenmem_access_t *access);
 int xc_altp2m_change_gfn(xc_interface *handle, uint32_t domid,
                          uint16_t view_id, xen_pfn_t old_gfn,
                          xen_pfn_t new_gfn);
diff --git a/tools/libxc/xc_altp2m.c b/tools/libxc/xc_altp2m.c
index ce4a1e4d60..0ddb18fa2c 100644
--- a/tools/libxc/xc_altp2m.c
+++ b/tools/libxc/xc_altp2m.c
@@ -177,9 +177,9 @@ int xc_altp2m_set_mem_access(xc_interface *handle, uint32_t domid,
     arg->version = HVMOP_ALTP2M_INTERFACE_VERSION;
     arg->cmd = HVMOP_altp2m_set_mem_access;
     arg->domain = domid;
-    arg->u.set_mem_access.view = view_id;
-    arg->u.set_mem_access.hvmmem_access = access;
-    arg->u.set_mem_access.gfn = gfn;
+    arg->u.mem_access.view = view_id;
+    arg->u.mem_access.hvmmem_access = access;
+    arg->u.mem_access.gfn = gfn;
 
     rc = xencall2(handle->xcall, __HYPERVISOR_hvm_op, HVMOP_altp2m,
 		  HYPERCALL_BUFFER_AS_ARG(arg));
@@ -254,3 +254,30 @@ int xc_altp2m_set_mem_access_multi(xc_interface *xch, uint32_t domid,
 
     return rc;
 }
+
+int xc_altp2m_get_mem_access(xc_interface *handle, uint32_t domid,
+                             uint16_t view_id, xen_pfn_t gfn,
+                             xenmem_access_t *access)
+{
+    int rc;
+    DECLARE_HYPERCALL_BUFFER(xen_hvm_altp2m_op_t, arg);
+
+    arg = xc_hypercall_buffer_alloc(handle, arg, sizeof(*arg));
+    if ( arg == NULL )
+        return -1;
+
+    arg->version = HVMOP_ALTP2M_INTERFACE_VERSION;
+    arg->cmd = HVMOP_altp2m_get_mem_access;
+    arg->domain = domid;
+    arg->u.mem_access.view = view_id;
+    arg->u.mem_access.gfn = gfn;
+
+    rc = xencall2(handle->xcall, __HYPERVISOR_hvm_op, HVMOP_altp2m,
+                 HYPERCALL_BUFFER_AS_ARG(arg));
+
+    if ( !rc )
+        *access = arg->u.mem_access.hvmmem_access;
+
+    xc_hypercall_buffer_free(handle, arg);
+    return rc;
+}
diff --git a/xen/arch/arm/mem_access.c b/xen/arch/arm/mem_access.c
index ba4ec780fd..178bc1a6c1 100644
--- a/xen/arch/arm/mem_access.c
+++ b/xen/arch/arm/mem_access.c
@@ -236,7 +236,7 @@ bool p2m_mem_access_check(paddr_t gpa, vaddr_t gla, const struct npfec npfec)
     if ( !p2m->mem_access_enabled )
         return true;
 
-    rc = p2m_get_mem_access(v->domain, gaddr_to_gfn(gpa), &xma);
+    rc = p2m_get_mem_access(v->domain, gaddr_to_gfn(gpa), &xma, 0);
     if ( rc )
         return true;
 
@@ -441,11 +441,15 @@ long p2m_set_mem_access_multi(struct domain *d,
 }
 
 int p2m_get_mem_access(struct domain *d, gfn_t gfn,
-                       xenmem_access_t *access)
+                       xenmem_access_t *access, unsigned int altp2m_idx)
 {
     int ret;
     struct p2m_domain *p2m = p2m_get_hostp2m(d);
 
+    /* altp2m is not yet implemented on Arm. The altp2m_idx should be 0. */
+    if ( altp2m_idx )
+        return -EINVAL;
+
     p2m_read_lock(p2m);
     ret = __p2m_get_mem_access(d, gfn, access);
     p2m_read_unlock(p2m);
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 67b99af334..49f4afabac 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4495,6 +4495,7 @@ static int do_altp2m_op(
     case HVMOP_altp2m_switch_p2m:
     case HVMOP_altp2m_set_mem_access:
     case HVMOP_altp2m_set_mem_access_multi:
+    case HVMOP_altp2m_get_mem_access:
     case HVMOP_altp2m_change_gfn:
         break;
 
@@ -4611,12 +4612,12 @@ static int do_altp2m_op(
         break;
 
     case HVMOP_altp2m_set_mem_access:
-        if ( a.u.set_mem_access.pad )
+        if ( a.u.mem_access.pad )
             rc = -EINVAL;
         else
-            rc = p2m_set_mem_access(d, _gfn(a.u.set_mem_access.gfn), 1, 0, 0,
-                                    a.u.set_mem_access.hvmmem_access,
-                                    a.u.set_mem_access.view);
+            rc = p2m_set_mem_access(d, _gfn(a.u.mem_access.gfn), 1, 0, 0,
+                                    a.u.mem_access.hvmmem_access,
+                                    a.u.mem_access.view);
         break;
 
     case HVMOP_altp2m_set_mem_access_multi:
@@ -4652,6 +4653,23 @@ static int do_altp2m_op(
         }
         break;
 
+    case HVMOP_altp2m_get_mem_access:
+        if ( a.u.mem_access.pad )
+            rc = -EINVAL;
+        else
+        {
+            xenmem_access_t access;
+
+            rc = p2m_get_mem_access(d, _gfn(a.u.mem_access.gfn), &access,
+                                    a.u.mem_access.view);
+            if ( !rc )
+            {
+                a.u.mem_access.hvmmem_access = access;
+                rc = __copy_to_guest(arg, &a, 1) ? -EFAULT : 0;
+            }
+        }
+        break;
+
     case HVMOP_altp2m_change_gfn:
         if ( a.u.change_gfn.pad1 || a.u.change_gfn.pad2 )
             rc = -EINVAL;
diff --git a/xen/arch/x86/mm/mem_access.c b/xen/arch/x86/mm/mem_access.c
index 03a8641569..d55825097a 100644
--- a/xen/arch/x86/mm/mem_access.c
+++ b/xen/arch/x86/mm/mem_access.c
@@ -467,9 +467,26 @@ long p2m_set_mem_access_multi(struct domain *d,
     return rc;
 }
 
-int p2m_get_mem_access(struct domain *d, gfn_t gfn, xenmem_access_t *access)
+int p2m_get_mem_access(struct domain *d, gfn_t gfn, xenmem_access_t *access,
+                       unsigned int altp2m_idx)
 {
-    struct p2m_domain *p2m = p2m_get_hostp2m(d);
+    struct p2m_domain *p2m;
+
+    if ( !altp2m_active(d) )
+    {
+        if ( altp2m_idx )
+            return -EINVAL;
+
+        p2m = p2m_get_hostp2m(d);
+    }
+    else
+    {
+        if ( altp2m_idx >= MAX_ALTP2M ||
+             d->arch.altp2m_eptp[altp2m_idx] == mfn_x(INVALID_MFN) )
+            return -EINVAL;
+
+        p2m = d->arch.altp2m_p2m[altp2m_idx];
+    }
 
     return _p2m_get_mem_access(p2m, gfn, access);
 }
diff --git a/xen/common/mem_access.c b/xen/common/mem_access.c
index 1bf6824442..010e6f8dbf 100644
--- a/xen/common/mem_access.c
+++ b/xen/common/mem_access.c
@@ -99,7 +99,7 @@ int mem_access_memop(unsigned long cmd,
         if ( (mao.pfn > domain_get_maximum_gpfn(d)) && mao.pfn != ~0ull )
             break;
 
-        rc = p2m_get_mem_access(d, _gfn(mao.pfn), &access);
+        rc = p2m_get_mem_access(d, _gfn(mao.pfn), &access, 0);
         if ( rc != 0 )
             break;
 
diff --git a/xen/include/public/hvm/hvm_op.h b/xen/include/public/hvm/hvm_op.h
index bbba99e5f5..36fd97f329 100644
--- a/xen/include/public/hvm/hvm_op.h
+++ b/xen/include/public/hvm/hvm_op.h
@@ -234,7 +234,7 @@ struct xen_hvm_altp2m_view {
 typedef struct xen_hvm_altp2m_view xen_hvm_altp2m_view_t;
 DEFINE_XEN_GUEST_HANDLE(xen_hvm_altp2m_view_t);
 
-struct xen_hvm_altp2m_set_mem_access {
+struct xen_hvm_altp2m_mem_access {
     /* view */
     uint16_t view;
     /* Memory type */
@@ -243,8 +243,8 @@ struct xen_hvm_altp2m_set_mem_access {
     /* gfn */
     uint64_t gfn;
 };
-typedef struct xen_hvm_altp2m_set_mem_access xen_hvm_altp2m_set_mem_access_t;
-DEFINE_XEN_GUEST_HANDLE(xen_hvm_altp2m_set_mem_access_t);
+typedef struct xen_hvm_altp2m_mem_access xen_hvm_altp2m_mem_access_t;
+DEFINE_XEN_GUEST_HANDLE(xen_hvm_altp2m_mem_access_t);
 
 struct xen_hvm_altp2m_set_mem_access_multi {
     /* view */
@@ -296,6 +296,8 @@ struct xen_hvm_altp2m_op {
 #define HVMOP_altp2m_change_gfn           8
 /* Set access for an array of pages */
 #define HVMOP_altp2m_set_mem_access_multi 9
+/* Get the access of a page of memory from a certain view */
+#define HVMOP_altp2m_get_mem_access       10
     domid_t domain;
     uint16_t pad1;
     uint32_t pad2;
@@ -303,7 +305,7 @@ struct xen_hvm_altp2m_op {
         struct xen_hvm_altp2m_domain_state         domain_state;
         struct xen_hvm_altp2m_vcpu_enable_notify   enable_notify;
         struct xen_hvm_altp2m_view                 view;
-        struct xen_hvm_altp2m_set_mem_access       set_mem_access;
+        struct xen_hvm_altp2m_mem_access           mem_access;
         struct xen_hvm_altp2m_change_gfn           change_gfn;
         struct xen_hvm_altp2m_set_mem_access_multi set_mem_access_multi;
         uint8_t pad[64];
diff --git a/xen/include/xen/mem_access.h b/xen/include/xen/mem_access.h
index 5ab34c1553..99fe11f6bc 100644
--- a/xen/include/xen/mem_access.h
+++ b/xen/include/xen/mem_access.h
@@ -76,7 +76,8 @@ long p2m_set_mem_access_multi(struct domain *d,
  * Get access type for a gfn.
  * If gfn == INVALID_GFN, gets the default access type.
  */
-int p2m_get_mem_access(struct domain *d, gfn_t gfn, xenmem_access_t *access);
+int p2m_get_mem_access(struct domain *d, gfn_t gfn, xenmem_access_t *access,
+                       unsigned int altp2m_idx);
 
 #ifdef CONFIG_HAS_MEM_ACCESS
 int mem_access_memop(unsigned long cmd,
-- 
2.17.0


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