[Xen-devel] [PATCH] Fix softtsc for AMD-V

[John Byrne <john.l.byrne@xxxxxx>]

The softtsc code for AMD does not update the ip; enabling it on AMD-V 
results in the domain spinning on the RDTSC instruction. The patch is 
against xen-unstable 18331.
Signed-off-by: John Byrne <john.l.byrne@xxxxxx>

diff -r d09404ad5730 xen/arch/x86/hvm/svm/emulate.c
--- a/xen/arch/x86/hvm/svm/emulate.c    Thu Aug 14 16:26:06 2008 +0100
+++ b/xen/arch/x86/hvm/svm/emulate.c    Thu Aug 14 12:05:44 2008 -0500
@@ -71,6 +71,7 @@ MAKE_INSTR(VMCALL, 3, 0x0f, 0x01, 0xd9);
 MAKE_INSTR(VMCALL, 3, 0x0f, 0x01, 0xd9);
 MAKE_INSTR(HLT,    1, 0xf4);
 MAKE_INSTR(INT3,   1, 0xcc);
+MAKE_INSTR(RDTSC,  2, 0x0f, 0x31);
 
 static const u8 *opc_bytes[INSTR_MAX_COUNT] = 
 {
@@ -81,7 +82,8 @@ static const u8 *opc_bytes[INSTR_MAX_COU
     [INSTR_WRMSR]  = OPCODE_WRMSR,
     [INSTR_VMCALL] = OPCODE_VMCALL,
     [INSTR_HLT]    = OPCODE_HLT,
-    [INSTR_INT3]   = OPCODE_INT3
+    [INSTR_INT3]   = OPCODE_INT3,
+    [INSTR_RDTSC]  = OPCODE_RDTSC
 };
 
 static int fetch(struct vcpu *v, u8 *buf, unsigned long addr, int len)
diff -r d09404ad5730 xen/arch/x86/hvm/svm/svm.c
--- a/xen/arch/x86/hvm/svm/svm.c        Thu Aug 14 16:26:06 2008 +0100
+++ b/xen/arch/x86/hvm/svm/svm.c        Thu Aug 14 12:05:44 2008 -0500
@@ -1128,6 +1128,17 @@ static void svm_vmexit_do_hlt(struct vmc
     hvm_hlt(regs->eflags);
 }
 
+static void svm_vmexit_do_rdtsc(struct cpu_user_regs *regs)
+{
+    unsigned int inst_len;
+
+    if ( (inst_len = __get_instruction_length(current, INSTR_RDTSC)) == 0 )
+        return;
+    __update_guest_eip(regs, inst_len);
+
+    hvm_rdtsc_intercept(regs);
+}
+
 static void wbinvd_ipi(void *info)
 {
     wbinvd();
@@ -1344,7 +1355,7 @@ asmlinkage void svm_vmexit_handler(struc
         break;
 
     case VMEXIT_RDTSC:
-        hvm_rdtsc_intercept(regs);
+        svm_vmexit_do_rdtsc(regs);
         break;
 
     case VMEXIT_RDTSCP:
diff -r d09404ad5730 xen/include/asm-x86/hvm/svm/emulate.h
--- a/xen/include/asm-x86/hvm/svm/emulate.h     Thu Aug 14 16:26:06 2008 +0100
+++ b/xen/include/asm-x86/hvm/svm/emulate.h     Thu Aug 14 12:05:45 2008 -0500
@@ -30,6 +30,7 @@ enum instruction_index {
     INSTR_VMCALL,
     INSTR_HLT,
     INSTR_INT3,
+    INSTR_RDTSC,
     INSTR_MAX_COUNT /* Must be last - Number of instructions supported */
 };
 

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