x86/fpu: Create a typedef for the x87/SSE area inside "struct xsave_struct"

Making the union non-anonymous would cause a lot of headaches, because a lot of
code relies on it being so, but it's possible to make a typedef of the anonymous
union so all callsites currently relying on typeof() can stop doing so directly.

This commit creates a `fpusse_t` typedef to the anonymous union at the head of
the XSAVE area and uses it instead of typeof().

No functional change.

Signed-off-by: Alejandro Vallejo <alejandro.vallejo@cloud.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/hvm/emulate.c

@@ -2363,8 +2363,7 @@ static int cf_check hvmemul_get_fpu(
         alternative_vcall(hvm_funcs.fpu_dirty_intercept);
     else if ( type == X86EMUL_FPU_fpu )
     {
-        const typeof(curr->arch.xsave_area->fpu_sse) *fpu_ctxt =
-            curr->arch.fpu_ctxt;
+        const fpusse_t *fpu_ctxt = curr->arch.fpu_ctxt;
 
         /*
          * Latch current register state so that we can back out changes
@@ -2404,7 +2403,7 @@ static void cf_check hvmemul_put_fpu(
 
     if ( aux )
     {
-        typeof(curr->arch.xsave_area->fpu_sse) *fpu_ctxt = curr->arch.fpu_ctxt;
+        fpusse_t *fpu_ctxt = curr->arch.fpu_ctxt;
         bool dval = aux->dval;
         int mode = hvm_guest_x86_mode(curr);
 

xen/arch/x86/i387.c

@@ -39,7 +39,7 @@ static inline void fpu_xrstor(struct vcpu *v, uint64_t mask)
 /* Restore x87 FPU, MMX, SSE and SSE2 state */
 static inline void fpu_fxrstor(struct vcpu *v)
 {
-    const typeof(v->arch.xsave_area->fpu_sse) *fpu_ctxt = v->arch.fpu_ctxt;
+    const fpusse_t *fpu_ctxt = v->arch.fpu_ctxt;
 
     /*
      * Some CPUs don't save/restore FDP/FIP/FOP unless an exception
@@ -151,7 +151,7 @@ static inline void fpu_xsave(struct vcpu *v)
 /* Save x87 FPU, MMX, SSE and SSE2 state */
 static inline void fpu_fxsave(struct vcpu *v)
 {
-    typeof(v->arch.xsave_area->fpu_sse) *fpu_ctxt = v->arch.fpu_ctxt;
+    fpusse_t *fpu_ctxt = v->arch.fpu_ctxt;
     unsigned int fip_width = v->domain->arch.x87_fip_width;
 
     if ( fip_width != 4 )
@@ -315,7 +315,7 @@ int vcpu_init_fpu(struct vcpu *v)
                                     __alignof(v->arch.xsave_area->fpu_sse));
         if ( v->arch.fpu_ctxt )
         {
-            typeof(v->arch.xsave_area->fpu_sse) *fpu_sse = v->arch.fpu_ctxt;
+            fpusse_t *fpu_sse = v->arch.fpu_ctxt;
 
             fpu_sse->fcw = FCW_DEFAULT;
             fpu_sse->mxcsr = MXCSR_DEFAULT;
@@ -336,7 +336,7 @@ void vcpu_setup_fpu(struct vcpu *v, struct xsave_struct *xsave_area,
      * accesses through both pointers alias one another, and the shorter form
      * is used here.
      */
-    typeof(xsave_area->fpu_sse) *fpu_sse = v->arch.fpu_ctxt;
+    fpusse_t *fpu_sse = v->arch.fpu_ctxt;
 
     ASSERT(!xsave_area || xsave_area == v->arch.xsave_area);
 

xen/arch/x86/include/asm/xstate.h

@@ -82,6 +82,8 @@ struct __attribute__((aligned (64))) xsave_struct
     char data[];                             /* Variable layout states */
 };
 
+typedef typeof(((struct xsave_struct){}).fpu_sse) fpusse_t;
+
 struct xstate_bndcsr {
     uint64_t bndcfgu;
     uint64_t bndstatus;

xen/arch/x86/xstate.c

@@ -846,7 +846,7 @@ void xstate_init(struct cpuinfo_x86 *c)
 
     if ( bsp )
     {
-        static typeof(current->arch.xsave_area->fpu_sse) __initdata ctxt;
+        static fpusse_t __initdata ctxt;
 
         asm ( "fxsave %0" : "=m" (ctxt) );
         if ( ctxt.mxcsr_mask )