[PATCH] KVM: MMU: Fix cmpxchg8b emulation

cmpxchg8b uses edx:eax as the compare operand, not edi:eax.

cmpxchg8b is used by 32-bit pae guests to set page table entries atomically,
and this is emulated touching shadowed guest page tables.

Also, implement it for 32-bit hosts.

Signed-off-by: Avi Kivity <avi@qumranet.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index cec1010..2e6bc56 100644 (file)
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -936,6 +936,30 @@ static int emulator_cmpxchg_emulated(unsigned long addr,
        return emulator_write_emulated(addr, new, bytes, ctxt);
 }
 
+#ifdef CONFIG_X86_32
+
+static int emulator_cmpxchg8b_emulated(unsigned long addr,
+                                      unsigned long old_lo,
+                                      unsigned long old_hi,
+                                      unsigned long new_lo,
+                                      unsigned long new_hi,
+                                      struct x86_emulate_ctxt *ctxt)
+{
+       static int reported;
+       int r;
+
+       if (!reported) {
+               reported = 1;
+               printk(KERN_WARNING "kvm: emulating exchange8b as write\n");
+       }
+       r = emulator_write_emulated(addr, new_lo, 4, ctxt);
+       if (r != X86EMUL_CONTINUE)
+               return r;
+       return emulator_write_emulated(addr+4, new_hi, 4, ctxt);
+}
+
+#endif
+
 static unsigned long get_segment_base(struct kvm_vcpu *vcpu, int seg)
 {
        return kvm_arch_ops->get_segment_base(vcpu, seg);
@@ -1010,6 +1034,9 @@ struct x86_emulate_ops emulate_ops = {
        .read_emulated       = emulator_read_emulated,
        .write_emulated      = emulator_write_emulated,
        .cmpxchg_emulated    = emulator_cmpxchg_emulated,
+#ifdef CONFIG_X86_32
+       .cmpxchg8b_emulated  = emulator_cmpxchg8b_emulated,
+#endif
 };
 
 int emulate_instruction(struct kvm_vcpu *vcpu,

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 1bff3e9..be70795 100644 (file)
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -1323,7 +1323,7 @@ twobyte_special_insn:
                                                         ctxt)) != 0))
                                goto done;
                        if ((old_lo != _regs[VCPU_REGS_RAX])
-                           || (old_hi != _regs[VCPU_REGS_RDI])) {
+                           || (old_hi != _regs[VCPU_REGS_RDX])) {
                                _regs[VCPU_REGS_RAX] = old_lo;
                                _regs[VCPU_REGS_RDX] = old_hi;
                                _eflags &= ~EFLG_ZF;