KVM: Clean up unloved invlpg emulation

invlpg shouldn't fetch the "src" address, since it may not be valid,
however SVM's "solution" which neuters emulation of all group 7
instruction is horrible and breaks kvm-lite.  The simplest fix is to
put a special check in for invlpg.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 3 insertions, 13 deletions

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 7439b3422ecf..342594d78d8c 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -213,19 +213,6 @@ static u16 twobyte_table[256] = {
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
 };
 
-/*
- * Tell the emulator that of the Group 7 instructions (sgdt, lidt, etc.) we
- * are interested only in invlpg and not in any of the rest.
- *
- * invlpg is a special instruction in that the data it references may not
- * be mapped.
- */
-void kvm_emulator_want_group7_invlpg(void)
-{
-        twobyte_table[1] &= ~SrcMem;
-}
-EXPORT_SYMBOL_GPL(kvm_emulator_want_group7_invlpg);
-
 /* Type, address-of, and value of an instruction's operand. */
 struct operand {
         enum { OP_REG, OP_MEM, OP_IMM } type;
@@ -791,6 +778,9 @@ done_prefixes:
                 goto srcmem_common;
         case SrcMem:
                 src.bytes = (d & ByteOp) ? 1 : op_bytes;
+                /* Don't fetch the address for invlpg: it could be unmapped. */
+                if (twobyte && b == 0x01 && modrm_reg == 7)
+                        break;
               srcmem_common:
                 src.type = OP_MEM;
                 src.ptr = (unsigned long *)cr2;