[Xen-changelog] [xen master] arm/hypercall: Use the common hcall_preempted boolean

[patchbot@xxxxxxx]

commit 9353e3628a8cba7edc5aea470b448f290af76118
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Feb 14 17:56:33 2017 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Thu Feb 16 14:15:25 2017 +0000

    arm/hypercall: Use the common hcall_preempted boolean
    
    With hcall_preempted having just been made common, ARM can use use it to
    simplify its hypercall handling.
    
    This simplifies the continuation logic and removes the risk of accidentally
    skipping multiple instructions.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
---
 xen/arch/arm/domain.c | 10 ++--------
 xen/arch/arm/traps.c  | 16 ++++++++--------
 2 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index 0010b8f..ee80334 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -348,17 +348,12 @@ void sync_vcpu_execstate(struct vcpu *v)
 
 void hypercall_cancel_continuation(void)
 {
-    struct cpu_user_regs *regs = guest_cpu_user_regs();
     struct mc_state *mcs = &current->mc_state;
 
     if ( mcs->flags & MCSF_in_multicall )
-    {
         __clear_bit(_MCSF_call_preempted, &mcs->flags);
-    }
     else
-    {
-        regs->pc += 4; /* undo re-execute 'hvc #XEN_HYPERCALL_TAG' */
-    }
+        current->hcall_preempted = false;
 }
 
 unsigned long hypercall_create_continuation(
@@ -390,8 +385,7 @@ unsigned long hypercall_create_continuation(
     {
         regs = guest_cpu_user_regs();
 
-        /* Ensure the hypercall trap instruction is re-executed. */
-        regs->pc -= 4;  /* re-execute 'hvc #XEN_HYPERCALL_TAG' */
+        current->hcall_preempted = true;
 
 #ifdef CONFIG_ARM_64
         if ( !is_32bit_domain(current->domain) )
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 718e820..729b012 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1453,9 +1453,6 @@ static void do_trap_hypercall(struct cpu_user_regs *regs, 
register_t *nr,
                               unsigned long iss)
 {
     arm_hypercall_fn_t call = NULL;
-#ifndef NDEBUG
-    register_t orig_pc = regs->pc;
-#endif
 
     BUILD_BUG_ON(NR_hypercalls < ARRAY_SIZE(arm_hypercall_table) );
 
@@ -1469,6 +1466,8 @@ static void do_trap_hypercall(struct cpu_user_regs *regs, 
register_t *nr,
         return;
     }
 
+    current->hcall_preempted = false;
+
     perfc_incra(hypercalls, *nr);
     call = arm_hypercall_table[*nr].fn;
     if ( call == NULL )
@@ -1480,12 +1479,9 @@ static void do_trap_hypercall(struct cpu_user_regs 
*regs, register_t *nr,
     HYPERCALL_RESULT_REG(regs) = call(HYPERCALL_ARGS(regs));
 
 #ifndef NDEBUG
-    /*
-     * Clobber argument registers only if pc is unchanged, otherwise
-     * this is a hypercall continuation.
-     */
-    if ( orig_pc == regs->pc )
+    if ( !current->hcall_preempted )
     {
+        /* Deliberately corrupt parameter regs used by this hypercall. */
         switch ( arm_hypercall_table[*nr].nr_args ) {
         case 5: HYPERCALL_ARG5(regs) = 0xDEADBEEF;
         case 4: HYPERCALL_ARG4(regs) = 0xDEADBEEF;
@@ -1498,6 +1494,10 @@ static void do_trap_hypercall(struct cpu_user_regs 
*regs, register_t *nr,
         *nr = 0xDEADBEEF;
     }
 #endif
+
+    /* Ensure the hypercall trap instruction is re-executed. */
+    if ( current->hcall_preempted )
+        regs->pc -= 4;  /* re-execute 'hvc #XEN_HYPERCALL_TAG' */
 }
 
 static bool check_multicall_32bit_clean(struct multicall_entry *multi)
--
generated by git-patchbot for /home/xen/git/xen.git#master

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