[Xen-devel] [PATCH] x86-64: pv wrmsr emulation fix

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

Make sure the upper 32 bits of RAX are disregarded during MSR write
emulation.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

Index: 2007-08-08/xen/arch/x86/traps.c
===================================================================
--- 2007-08-08.orig/xen/arch/x86/traps.c        2007-08-08 11:37:08.000000000 
+0200
+++ 2007-08-08/xen/arch/x86/traps.c     2007-08-08 11:40:02.000000000 +0200
@@ -1696,6 +1696,8 @@ static int emulate_privileged_op(struct 
         break;
 
     case 0x30: /* WRMSR */
+        data = regs->eax;
+        res = ((u64)regs->edx << 32) | data;
         switch ( regs->ecx )
         {
 #ifdef CONFIG_X86_64
@@ -1704,24 +1706,21 @@ static int emulate_privileged_op(struct 
                 goto fail;
             if ( wrmsr_safe(MSR_FS_BASE, regs->eax, regs->edx) )
                 goto fail;
-            v->arch.guest_context.fs_base =
-                ((u64)regs->edx << 32) | regs->eax;
+            v->arch.guest_context.fs_base = res;
             break;
         case MSR_GS_BASE:
             if ( is_pv_32on64_vcpu(v) )
                 goto fail;
             if ( wrmsr_safe(MSR_GS_BASE, regs->eax, regs->edx) )
                 goto fail;
-            v->arch.guest_context.gs_base_kernel =
-                ((u64)regs->edx << 32) | regs->eax;
+            v->arch.guest_context.gs_base_kernel = res;
             break;
         case MSR_SHADOW_GS_BASE:
             if ( is_pv_32on64_vcpu(v) )
                 goto fail;
             if ( wrmsr_safe(MSR_SHADOW_GS_BASE, regs->eax, regs->edx) )
                 goto fail;
-            v->arch.guest_context.gs_base_user =
-                ((u64)regs->edx << 32) | regs->eax;
+            v->arch.guest_context.gs_base_user = res;
             break;
 #endif
         default:




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