KVM: x86: POPA emulation may not clear bits [63:32]

POPA should assign the values to the registers as usual registers are assigned.
In other words, 32-bits register assignments should clear bits [63:32] of the
register.

Split the code of register assignments that will be used by future changes as
well.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Message-Id: <1427719163-5429-3-git-send-email-namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 23 insertions, 16 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 62f7a395717d..4961dc5eb303 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -478,6 +478,25 @@ static void assign_masked(ulong *dest, ulong src, ulong mask)
         *dest = (*dest & ~mask) | (src & mask);
 }
 
+static void assign_register(unsigned long *reg, u64 val, int bytes)
+{
+        /* The 4-byte case *is* correct: in 64-bit mode we zero-extend. */
+        switch (bytes) {
+        case 1:
+                *(u8 *)reg = (u8)val;
+                break;
+        case 2:
+                *(u16 *)reg = (u16)val;
+                break;
+        case 4:
+                *reg = (u32)val;
+                break;  /* 64b: zero-extend */
+        case 8:
+                *reg = val;
+                break;
+        }
+}
+
 static inline unsigned long ad_mask(struct x86_emulate_ctxt *ctxt)
 {
         return (1UL << (ctxt->ad_bytes << 3)) - 1;
@@ -1691,21 +1710,7 @@ static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
 
 static void write_register_operand(struct operand *op)
 {
-        /* The 4-byte case *is* correct: in 64-bit mode we zero-extend. */
-        switch (op->bytes) {
-        case 1:
-                *(u8 *)op->addr.reg = (u8)op->val;
-                break;
-        case 2:
-                *(u16 *)op->addr.reg = (u16)op->val;
-                break;
-        case 4:
-                *op->addr.reg = (u32)op->val;
-                break;  /* 64b: zero-extend */
-        case 8:
-                *op->addr.reg = op->val;
-                break;
-        }
+        return assign_register(op->addr.reg, op->val, op->bytes);
 }
 
 static int writeback(struct x86_emulate_ctxt *ctxt, struct operand *op)
@@ -1926,6 +1931,7 @@ static int em_popa(struct x86_emulate_ctxt *ctxt)
 {
         int rc = X86EMUL_CONTINUE;
         int reg = VCPU_REGS_RDI;
+        u32 val;
 
         while (reg >= VCPU_REGS_RAX) {
                 if (reg == VCPU_REGS_RSP) {
@@ -1933,9 +1939,10 @@ static int em_popa(struct x86_emulate_ctxt *ctxt)
                         --reg;
                 }
 
-                rc = emulate_pop(ctxt, reg_rmw(ctxt, reg), ctxt->op_bytes);
+                rc = emulate_pop(ctxt, &val, ctxt->op_bytes);
                 if (rc != X86EMUL_CONTINUE)
                         break;
+                assign_register(reg_rmw(ctxt, reg), val, ctxt->op_bytes);
                 --reg;
         }
         return rc;