kernel/x86_64: Use VZEROALL to clear XMM/YMM/etc. registers when available.

It comes with AVX, so enable it if we've enabled AVX.

This also adjusts altcodepatch_replace to explicitly set NOPs
for the remainder of the patch area.

Change-Id: Ia07549851d86836ff5428635b580c751b4e5b2a3
Reviewed-on: https://review.haiku-os.org/c/haiku/+/10867
Reviewed-by: waddlesplash <[email protected]>
Reviewed-by: Jérôme Duval <[email protected]>
Tested-by: Commit checker robot <[email protected]>

headers/private/kernel/arch/x86/arch_altcodepatch.h

@@ -24,6 +24,7 @@
 #define ALTCODEPATCH_TAG_CLAC		2
 #define ALTCODEPATCH_TAG_XSAVE		3
 #define ALTCODEPATCH_TAG_XRSTOR		4
+#define ALTCODEPATCH_TAG_CLEAR_FPU	5
 
 
 #ifdef _ASSEMBLER

src/system/kernel/arch/x86/64/interrupts.S

@@ -118,6 +118,7 @@
   1:
 
 #define CLEAR_FPU_STATE() \
+	CODEPATCH_START \
 	pxor %xmm0, %xmm0; \
 	pxor %xmm1, %xmm1; \
 	pxor %xmm2, %xmm2; \
@@ -133,7 +134,8 @@
 	pxor %xmm12, %xmm12; \
 	pxor %xmm13, %xmm13; \
 	pxor %xmm14, %xmm14; \
-	pxor %xmm15, %xmm15
+	pxor %xmm15, %xmm15; \
+	CODEPATCH_END(ALTCODEPATCH_TAG_CLEAR_FPU)
 
 // The following code defines the interrupt service routines for all 256
 // interrupts. It creates a block of handlers, each 16 bytes, that the IDT

src/system/kernel/arch/x86/64/stubs.S

@@ -28,3 +28,7 @@ FUNCTION_END(_xsavec)
 FUNCTION(_xrstor):
 	xrstor64	(%rdi)
 FUNCTION_END(_xrstor)
+
+FUNCTION(_vzeroall):
+	vzeroall
+FUNCTION_END(_vzeroall)

src/system/kernel/arch/x86/arch_altcodepatch.cpp

@@ -45,7 +45,9 @@ arch_altcodepatch_replace(uint16 tag, void* newcodepatch, size_t length)
 		void* address = (void*)(KERNEL_LOAD_BASE + patch->kernel_offset);
 		if (patch->length < length)
 			panic("can't copy patch: new code is too long\n");
+
 		memcpy(address, newcodepatch, length);
+		memset((uint8*)address + length, 0x90 /* nop */, patch->length - length);
 		count++;
 	}
 

src/system/kernel/arch/x86/arch_cpu.cpp

@@ -88,6 +88,7 @@ extern addr_t _clac;
 extern addr_t _xsave;
 extern addr_t _xsavec;
 extern addr_t _xrstor;
+extern addr_t _vzeroall;
 uint64 gXsaveMask;
 uint64 gFPUSaveLength = 512;
 bool gHasXsave = false;
@@ -1944,6 +1945,9 @@ arch_cpu_init_post_vm(kernel_args* args)
 		arch_altcodepatch_replace(ALTCODEPATCH_TAG_XRSTOR,
 			&_xrstor, 4);
 
+		if ((gXsaveMask & IA32_XCR0_AVX) != 0)
+			arch_altcodepatch_replace(ALTCODEPATCH_TAG_CLEAR_FPU, &_vzeroall, 3);
+
 		dprintf("enable %s 0x%" B_PRIx64 " %" B_PRId64 "\n",
 			gHasXsavec ? "XSAVEC" : "XSAVE", gXsaveMask, gFPUSaveLength);
 	}