nvmm: Implement FPU save/restore.

Otherwise, the host won't be able to modify the guest FPU (and we could
clobber the state, too.)

This doesn't seem to fix the general problems seen so far, however.

src/add-ons/kernel/drivers/nvmm/nvmm_haiku.cpp

@@ -68,6 +68,42 @@ haiku_get_xsave_mask()
 }
 
 
+extern "C" void
+haiku_save_fpu(void* area, uint64_t xsave_features)
+{
+	switch (xsave_features) {
+		case IA32_XCR0_X87:
+			asm volatile("fnsave %0" : "=m" (*(char*)area));
+			break;
+
+		case IA32_XCR0_X87 | IA32_XCR0_SSE:
+			asm volatile("fxsaveq %0" : "=m" (*(char*)area));
+			break;
+
+		default:
+			panic("nvmm save_fpu: unimplemented xsave_features state");
+	}
+}
+
+
+extern "C" void
+haiku_restore_fpu(const void* area, uint64_t xsave_features)
+{
+	switch (xsave_features) {
+		case IA32_XCR0_X87:
+			asm volatile("frstor %0" :: "m" (*(const char*)area));
+			break;
+
+		case IA32_XCR0_X87 | IA32_XCR0_SSE:
+			asm volatile("fxrstorq %0" :: "m" (*(const char*)area));
+			break;
+
+		default:
+			panic("nvmm restore_fpu: unimplemented xsave_features state");
+	}
+}
+
+
 extern "C" int32
 haiku_smp_get_current_cpu()
 {

src/add-ons/kernel/drivers/nvmm/x86/nvmm_x86.h

@@ -908,9 +908,13 @@ void x86_curthread_restore_dbregs(uint64_t *drs);
 		fpurstor((union savefpu *)(a), m);	\
 	})
 #elif defined(__HAIKU__)
-// Haiku allows floating point in kernel, we don't need to save and restore FPU
-#define x86_save_fpu(a, m)
-#define x86_restore_fpu(a, m)
+#define x86_curthread_save_fpu()	// Haiku allows FPU usage in the kernel, thus
+#define x86_curthread_restore_fpu()	// save/restore of thread FPU state not needed.
+
+void haiku_save_fpu(void* area, uint64_t xsave_features);
+void haiku_restore_fpu(const void* area, uint64_t xsave_features);
+#define x86_save_fpu haiku_save_fpu
+#define x86_restore_fpu haiku_restore_fpu
 #endif
 
 /* XCRs. */