[PATCH 2 of 2] xen: hvm_save: Add pre-3.4 compatibility for hvm_hw_cpu

[George Dunlap <george.dunlap@eu.citrix.com>]

Xen 4.0 added "msr_tsc_aux" in the middle of the hvm_hw_cpu structure, making
it incompatible with pre-3.4 savefiles.  This patch uses the recently introduced
backwards-compatibility infrastructure to convert the old to the new.

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>

diff -r ba5c95ba74d3 -r e2f2377fedef xen/include/public/arch-x86/hvm/save.h
--- a/xen/include/public/arch-x86/hvm/save.h	Thu Mar 31 15:21:21 2011 +0100
+++ b/xen/include/public/arch-x86/hvm/save.h	Thu Mar 31 15:21:21 2011 +0100
@@ -46,6 +46,8 @@
 
 /*
  * Processor
+ *
+ * Compat: Pre-3.4 didn't have msr_tsc_aux
  */
 
 struct hvm_hw_cpu {
@@ -157,8 +159,131 @@
     uint32_t error_code;
 };
 
-DECLARE_HVM_SAVE_TYPE(CPU, 2, struct hvm_hw_cpu);
+struct hvm_hw_cpu_compat {
+    uint8_t  fpu_regs[512];
 
+    uint64_t rax;
+    uint64_t rbx;
+    uint64_t rcx;
+    uint64_t rdx;
+    uint64_t rbp;
+    uint64_t rsi;
+    uint64_t rdi;
+    uint64_t rsp;
+    uint64_t r8;
+    uint64_t r9;
+    uint64_t r10;
+    uint64_t r11;
+    uint64_t r12;
+    uint64_t r13;
+    uint64_t r14;
+    uint64_t r15;
+
+    uint64_t rip;
+    uint64_t rflags;
+
+    uint64_t cr0;
+    uint64_t cr2;
+    uint64_t cr3;
+    uint64_t cr4;
+
+    uint64_t dr0;
+    uint64_t dr1;
+    uint64_t dr2;
+    uint64_t dr3;
+    uint64_t dr6;
+    uint64_t dr7;    
+
+    uint32_t cs_sel;
+    uint32_t ds_sel;
+    uint32_t es_sel;
+    uint32_t fs_sel;
+    uint32_t gs_sel;
+    uint32_t ss_sel;
+    uint32_t tr_sel;
+    uint32_t ldtr_sel;
+
+    uint32_t cs_limit;
+    uint32_t ds_limit;
+    uint32_t es_limit;
+    uint32_t fs_limit;
+    uint32_t gs_limit;
+    uint32_t ss_limit;
+    uint32_t tr_limit;
+    uint32_t ldtr_limit;
+    uint32_t idtr_limit;
+    uint32_t gdtr_limit;
+
+    uint64_t cs_base;
+    uint64_t ds_base;
+    uint64_t es_base;
+    uint64_t fs_base;
+    uint64_t gs_base;
+    uint64_t ss_base;
+    uint64_t tr_base;
+    uint64_t ldtr_base;
+    uint64_t idtr_base;
+    uint64_t gdtr_base;
+
+    uint32_t cs_arbytes;
+    uint32_t ds_arbytes;
+    uint32_t es_arbytes;
+    uint32_t fs_arbytes;
+    uint32_t gs_arbytes;
+    uint32_t ss_arbytes;
+    uint32_t tr_arbytes;
+    uint32_t ldtr_arbytes;
+
+    uint64_t sysenter_cs;
+    uint64_t sysenter_esp;
+    uint64_t sysenter_eip;
+
+    /* msr for em64t */
+    uint64_t shadow_gs;
+
+    /* msr content saved/restored. */
+    uint64_t msr_flags;
+    uint64_t msr_lstar;
+    uint64_t msr_star;
+    uint64_t msr_cstar;
+    uint64_t msr_syscall_mask;
+    uint64_t msr_efer;
+    /*uint64_t msr_tsc_aux; COMPAT */
+
+    /* guest's idea of what rdtsc() would return */
+    uint64_t tsc;
+
+    /* pending event, if any */
+    union {
+        uint32_t pending_event;
+        struct {
+            uint8_t  pending_vector:8;
+            uint8_t  pending_type:3;
+            uint8_t  pending_error_valid:1;
+            uint32_t pending_reserved:19;
+            uint8_t  pending_valid:1;
+        };
+    };
+    /* error code for pending event */
+    uint32_t error_code;
+};
+
+static inline int _hvm_hw_fix_cpu(void *h) {
+    struct hvm_hw_cpu *new=h;
+    struct hvm_hw_cpu_compat *old=h;
+
+    /* If we copy from the end backwards, we should
+     * be able to do the modification in-place */
+    new->error_code=old->error_code;
+    new->pending_event=old->pending_event;
+    new->tsc=old->tsc;
+    new->msr_tsc_aux=0;
+
+    return 0;
+}
+
+DECLARE_HVM_SAVE_TYPE_COMPAT(CPU, 2, struct hvm_hw_cpu, \
+                             struct hvm_hw_cpu_compat, _hvm_hw_fix_cpu);
 
 /*
  * PIC