[xen staging] x86emul: extend x86_insn_is_mem_write() coverage

[patchbot@xxxxxxx]

commit fc6fa977be54a24a1325e3f2d08b1b1dcb675f44
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue May 5 09:50:54 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue May 5 09:50:54 2020 +0200

    x86emul: extend x86_insn_is_mem_write() coverage
    
    Several insns were missed when this function was first added. As far as
    insns already supported by the emulator go - SMSW and {,V}STMXCSR were
    wrongly considered r/o insns so far.
    
    Insns like the VMX, SVM, or CET-SS ones, PTWRITE, or AMD's new SNP ones
    are intentionally not covered just yet. VMPTRST is put there just to
    complete the respective group.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/x86_emulate/x86_emulate.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c 
b/xen/arch/x86/x86_emulate/x86_emulate.c
index 1959fc227a..7503da980f 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -11551,13 +11551,39 @@ x86_insn_is_mem_write(const struct x86_emulate_state 
*state,
         break;
 
     case X86EMUL_OPC(0x0f, 0x01):
-        return !(state->modrm_reg & 6); /* SGDT / SIDT */
+        switch ( state->modrm_reg & 7 )
+        {
+        case 0: /* SGDT */
+        case 1: /* SIDT */
+        case 4: /* SMSW */
+            return true;
+        }
+        break;
+
+    case X86EMUL_OPC(0x0f, 0xae):
+        switch ( state->modrm_reg & 7 )
+        {
+        case 0: /* FXSAVE */
+        case 3: /* {,V}STMXCSR */
+        case 4: /* XSAVE */
+        case 6: /* XSAVEOPT */
+            return true;
+        }
+        break;
 
     case X86EMUL_OPC(0x0f, 0xba):
         return (state->modrm_reg & 7) > 4; /* BTS / BTR / BTC */
 
     case X86EMUL_OPC(0x0f, 0xc7):
-        return (state->modrm_reg & 7) == 1; /* CMPXCHG{8,16}B */
+        switch ( state->modrm_reg & 7 )
+        {
+        case 1: /* CMPXCHG{8,16}B */
+        case 4: /* XSAVEC */
+        case 5: /* XSAVES */
+        case 7: /* VMPTRST */
+            return true;
+        }
+        break;
     }
 
     return false;
--
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