[Xen-devel] [PATCH] enable tmem functionality for PV on HVM guests

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

(Keir, please also apply for 4.0.1 if it's not too late.)

Enable tmem functionality for PV on HVM guests.  Guest kernel
must still be tmem-enabled to use this functionality (e.g.
won't work for Windows), but upstream Linux tmem (aka
cleancache and frontswap) patches apply cleanly on top
of PV on HVM patches.

Also, fix up some ASSERTS and code used only when bad guest
mfns are passed to tmem.  Previous code could crash Xen
if a buggy/malicious guest passes bad gmfns.

Signed-off-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>

diff -r ba2c0eecaf7f xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c    Tue Jun 15 11:31:43 2010 +0100
+++ b/xen/arch/x86/hvm/hvm.c    Mon Jun 21 10:37:05 2010 -0600
@@ -2265,7 +2265,8 @@ static hvm_hypercall_t *hvm_hypercall32_
     HYPERCALL(xen_version),
     HYPERCALL(event_channel_op),
     HYPERCALL(sched_op),
-    HYPERCALL(hvm_op)
+    HYPERCALL(hvm_op),
+    HYPERCALL(tmem_op)
 };
 
 #else /* defined(__x86_64__) */
@@ -2313,7 +2314,8 @@ static hvm_hypercall_t *hvm_hypercall64_
     HYPERCALL(xen_version),
     HYPERCALL(event_channel_op),
     HYPERCALL(sched_op),
-    HYPERCALL(hvm_op)
+    HYPERCALL(hvm_op),
+    HYPERCALL(tmem_op)
 };
 
 static hvm_hypercall_t *hvm_hypercall32_table[NR_hypercalls] = {
@@ -2323,7 +2325,8 @@ static hvm_hypercall_t *hvm_hypercall32_
     HYPERCALL(xen_version),
     HYPERCALL(event_channel_op),
     HYPERCALL(sched_op),
-    HYPERCALL(hvm_op)
+    HYPERCALL(hvm_op),
+    HYPERCALL(tmem_op)
 };
 
 #endif /* defined(__x86_64__) */
diff -r ba2c0eecaf7f xen/common/tmem.c
--- a/xen/common/tmem.c Tue Jun 15 11:31:43 2010 +0100
+++ b/xen/common/tmem.c Mon Jun 21 10:37:05 2010 -0600
@@ -1483,6 +1483,7 @@ copy_uncompressed:
         pgp_free_data(pgp, pool);
     if ( ( pgp->pfp = tmem_page_alloc(pool) ) == NULL )
         goto failed_dup;
+    pgp->size = 0;
     /* tmh_copy_from_client properly handles len==0 and offsets != 0 */
     ret = tmh_copy_from_client(pgp->pfp,cmfn,tmem_offset,pfn_offset,len,0);
     if ( ret == -EFAULT )
@@ -1492,7 +1493,6 @@ copy_uncompressed:
         if ( pcd_associate(pgp,NULL,0) == -ENOMEM )
             goto failed_dup;
     }
-    pgp->size = 0;
 
 done:
     /* successfully replaced data, clean up and return success */
@@ -1509,12 +1509,14 @@ bad_copy:
 bad_copy:
     /* this should only happen if the client passed a bad mfn */
     failed_copies++;
-ASSERT(0);
-    return -EFAULT;
+    ret = -EFAULT;
+    goto cleanup;
 
 failed_dup:
    /* couldn't change out the data, flush the old data and return
     * -ENOSPC instead of -ENOMEM to differentiate failed _dup_ put */
+    ret = -ENOSPC;
+cleanup:
     pgpfound = pgp_delete_from_obj(obj, pgp->index);
     ASSERT(pgpfound == pgp);
     pgp_delete(pgpfound,0);
@@ -1528,7 +1530,7 @@ failed_dup:
         tmem_spin_unlock(&obj->obj_spinlock);
     }
     pool->dup_puts_flushed++;
-    return -ENOSPC;
+    return ret;
 }
 
 
@@ -1579,6 +1581,7 @@ static NOINLINE int do_tmem_put(pool_t *
         goto free;
     ASSERT(ret != -EEXIST);
     pgp->index = index;
+    pgp->size = 0;
 
     if ( len != 0 && client->compress )
     {
@@ -1615,7 +1618,6 @@ copy_uncompressed:
         if ( pcd_associate(pgp,NULL,0) == -ENOMEM )
             goto delete_and_free;
     }
-    pgp->size = 0;
 
 insert_page:
     if ( is_ephemeral(pool) )
@@ -1648,6 +1650,11 @@ insert_page:
         tot_good_eph_puts++;
     return 1;
 
+bad_copy:
+    /* this should only happen if the client passed a bad mfn */
+    ret = -EFAULT;
+    failed_copies++;
+
 delete_and_free:
     ASSERT((obj != NULL) && (pgp != NULL) && (pgp->index != -1));
     pgpdel = pgp_delete_from_obj(obj, pgp->index);
@@ -1669,12 +1676,6 @@ free:
     }
     pool->no_mem_puts++;
     return ret;
-
-bad_copy:
-    /* this should only happen if the client passed a bad mfn */
-    failed_copies++;
-ASSERT(0);
-    goto free;
 }
 
 static NOINLINE int do_tmem_get(pool_t *pool, uint64_t oid, uint32_t index,
@@ -1758,7 +1759,6 @@ bad_copy:
 bad_copy:
     /* this should only happen if the client passed a bad mfn */
     failed_copies++;
-ASSERT(0);
     return -EFAULT;
 
 }
diff -r ba2c0eecaf7f xen/common/tmem_xen.c
--- a/xen/common/tmem_xen.c     Tue Jun 15 11:31:43 2010 +0100
+++ b/xen/common/tmem_xen.c     Mon Jun 21 10:37:05 2010 -0600
@@ -100,7 +100,7 @@ static inline void *cli_mfn_to_va(tmem_c
     p2m_type_t t;
 
     cli_mfn = mfn_x(gfn_to_mfn(current->domain, cmfn, &t));
-    if (t != p2m_ram_rw)
+    if (t != p2m_ram_rw || cli_mfn == INVALID_MFN)
         return NULL;
     if (pcli_mfn != NULL)
         *pcli_mfn = cli_mfn;
diff -r ba2c0eecaf7f xen/include/xen/tmem_xen.h
--- a/xen/include/xen/tmem_xen.h        Tue Jun 15 11:31:43 2010 +0100
+++ b/xen/include/xen/tmem_xen.h        Mon Jun 21 10:37:05 2010 -0600
@@ -456,7 +456,9 @@ static inline int tmh_get_tmemop_from_cl
 static inline int tmh_get_tmemop_from_client(tmem_op_t *op, tmem_cli_op_t uops)
 {
 #ifdef CONFIG_COMPAT
-    if ( is_pv_32on64_vcpu(current) )
+    if ( is_hvm_vcpu(current) ?
+         hvm_guest_x86_mode(current) != 8 :
+         is_pv_32on64_vcpu(current) )
     {
         int rc;
         enum XLAT_tmem_op_u u;

Attachment: tmem-hvm.patch
Description: Binary data

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