[Xen-devel] [PATCH] vmx_fpu.patch

[Arun Sharma <arun.sharma@xxxxxxxxx>]

Implement a eager save/lazy restore algorithm for dealing with the FP state of 
a VMX guest.

Signed-off-by: Xin B Li <xin.b.li@xxxxxxxxx>
Signed-off-by: Asit Mallick <asit.k.mallick@xxxxxxxxx>
Signed-off-by: Arun Sharma <arun.sharma@xxxxxxxxx>

--- 1.171/xen/arch/x86/traps.c  2005-05-10 03:53:31 -07:00
+++ edited/xen/arch/x86/traps.c 2005-05-11 11:09:00 -07:00
@@ -917,15 +917,7 @@
 asmlinkage int math_state_restore(struct cpu_user_regs *regs)
 {
     /* Prevent recursion. */
-    clts();
-
-    if ( !test_and_set_bit(EDF_USEDFPU, &current->flags) )
-    {
-        if ( test_bit(EDF_DONEFPUINIT, &current->flags) )
-            restore_fpu(current);
-        else
-            init_fpu();
-    }
+    do_clts();
 
     if ( test_and_clear_bit(EDF_GUEST_STTS, &current->flags) )
     {
===== xen/arch/x86/vmx.c 1.48 vs edited =====
--- 1.48/xen/arch/x86/vmx.c     2005-05-09 07:33:15 -07:00
+++ edited/xen/arch/x86/vmx.c   2005-05-11 11:09:28 -07:00
@@ -154,6 +154,20 @@
     return result;
 }
 
+static void vmx_do_no_device_fault() 
+{
+    unsigned long cr0;
+        
+    do_clts();
+    __vmread(CR0_READ_SHADOW, &cr0);
+    if (!(cr0 & X86_CR0_TS)) {
+        __vmread(GUEST_CR0, &cr0);
+        cr0 &= ~X86_CR0_TS;
+        __vmwrite(GUEST_CR0, cr0);
+    }
+    __vmwrite(EXCEPTION_BITMAP, MONITOR_DEFAULT_EXCEPTION_BITMAP);
+}
+
 static void vmx_do_general_protection_fault(struct cpu_user_regs *regs) 
 {
     unsigned long eip, error_code;
@@ -894,6 +908,8 @@
         mov_from_cr(cr, gp, regs);
         break;
     case TYPE_CLTS:
+        do_clts();
+
         __vmread(GUEST_CR0, &value);
         value &= ~X86_CR0_TS; /* clear TS */
         __vmwrite(GUEST_CR0, value);
@@ -1093,6 +1109,11 @@
             break;
         }
 #endif
+        case TRAP_no_device:
+        {
+            vmx_do_no_device_fault();
+            break;  
+        }
         case TRAP_gp_fault:
         {
             vmx_do_general_protection_fault(&regs);
===== xen/arch/x86/vmx_io.c 1.22 vs edited =====
--- 1.22/xen/arch/x86/vmx_io.c  2005-04-28 07:04:10 -07:00
+++ edited/xen/arch/x86/vmx_io.c        2005-05-11 11:02:52 -07:00
@@ -429,6 +429,7 @@
 
 void vmx_do_resume(struct exec_domain *d) 
 {
+    vmx_stts();
     if ( test_bit(VMX_CPU_STATE_PG_ENABLED, &d->arch.arch_vmx.cpu_state) )
         __vmwrite(GUEST_CR3, pagetable_val(d->arch.shadow_table));
     else
===== xen/arch/x86/vmx_vmcs.c 1.21 vs edited =====
--- 1.21/xen/arch/x86/vmx_vmcs.c        2005-04-28 07:04:10 -07:00
+++ edited/xen/arch/x86/vmx_vmcs.c      2005-05-11 11:05:12 -07:00
@@ -164,6 +164,9 @@
     struct pfn_info *page;
     struct cpu_user_regs *regs = get_cpu_user_regs();
 
+    vmx_stts();
+    set_bit(EDF_GUEST_STTS, &ed->flags);
+
     cpu = smp_processor_id();
 
     page = (struct pfn_info *) alloc_domheap_page(NULL);
===== xen/include/asm-x86/i387.h 1.9 vs edited =====
--- 1.9/xen/include/asm-x86/i387.h      2005-05-08 05:06:08 -07:00
+++ edited/xen/include/asm-x86/i387.h   2005-05-11 11:16:26 -07:00
@@ -28,4 +28,17 @@
     __asm__ __volatile__ ( "ldmxcsr %0" : : "m" (__mxcsr) ); \
 } while ( 0 )
 
+/* Make current domain the FPU owner */
+static inline void do_clts()
+{
+    clts();
+    if ( !test_and_set_bit(EDF_USEDFPU, &current->flags) )
+    {
+        if ( test_bit(EDF_DONEFPUINIT, &current->flags) )
+            restore_fpu(current);
+        else
+            init_fpu();
+    }
+}
+
 #endif /* __ASM_I386_I387_H */
===== xen/include/asm-x86/vmx.h 1.6 vs edited =====
--- 1.6/xen/include/asm-x86/vmx.h       2005-04-28 07:04:11 -07:00
+++ edited/xen/include/asm-x86/vmx.h    2005-05-11 11:13:28 -07:00
@@ -24,6 +24,7 @@
 #include <asm/regs.h>
 #include <asm/processor.h>
 #include <asm/vmx_vmcs.h>
+#include <asm/i387.h>
 
 extern void vmx_asm_vmexit_handler(struct cpu_user_regs);
 extern void vmx_asm_do_resume(void);
@@ -251,4 +252,19 @@
     return 0;
 }
 
+/* Make sure that xen intercepts any FP accesses from current */
+static inline void vmx_stts()
+{
+    unsigned long cr0;
+
+    __vmread(GUEST_CR0, &cr0);
+    if (!(cr0 & X86_CR0_TS))
+        __vmwrite(GUEST_CR0, cr0 | X86_CR0_TS);
+
+    __vmread(CR0_READ_SHADOW, &cr0);
+    if (!(cr0 & X86_CR0_TS))
+       __vmwrite(EXCEPTION_BITMAP, MONITOR_DEFAULT_EXCEPTION_BITMAP | 
+                                   EXCEPTION_BITMAP_NM);
+}
+ 
 #endif /* __ASM_X86_VMX_H__ */

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