While for us it's not as bad as it was for Linux, their commit
13e457e0ee ("KVM: x86: Emulator does not decode clflush well", by
Nadav Amit <na...@cs.technion.ac.il>) nevertheless points out two
shortcomings in our code: opcode 0F AE /7 is clflush only when it uses
a memory mode (otherwise it's SFENCE) and when there's no REP prefix
(an operand size prefix is fine, as that's CLFLUSHOPT).
Signed-off-by: Jan Beulich <jbeul...@suse.com>
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -4400,7 +4400,9 @@ x86_emulate(
case 0xae: /* Grp15 */
switch ( modrm_reg & 7 )
{
- case 7: /* clflush */
+ case 7: /* clflush{,opt} */
+ fail_if(modrm_mod == 3);
+ fail_if(rep_prefix());
fail_if(ops->wbinvd == NULL);
if ( (rc = ops->wbinvd(ctxt)) != 0 )
goto done;
x86emul: tighten CLFLUSH emulation
While for us it's not as bad as it was for Linux, their commit
13e457e0ee ("KVM: x86: Emulator does not decode clflush well", by
Nadav Amit <na...@cs.technion.ac.il>) nevertheless points out two
shortcomings in our code: opcode 0F AE /7 is clflush only when it uses
a memory mode (otherwise it's SFENCE) and when there's no REP prefix
(an operand size prefix is fine, as that's CLFLUSHOPT).
Signed-off-by: Jan Beulich <jbeul...@suse.com>
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -4400,7 +4400,9 @@ x86_emulate(
case 0xae: /* Grp15 */
switch ( modrm_reg & 7 )
{
- case 7: /* clflush */
+ case 7: /* clflush{,opt} */
+ fail_if(modrm_mod == 3);
+ fail_if(rep_prefix());
fail_if(ops->wbinvd == NULL);
if ( (rc = ops->wbinvd(ctxt)) != 0 )
goto done;
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