powerpc/64s: Remove PROT_SAO support

ISA v3.1 does not support the SAO storage control attribute required to
implement PROT_SAO. PROT_SAO was used by specialised system software
(Lx86) that has been discontinued for about 7 years, and is not thought
to be used elsewhere, so removal should not cause problems.

We rather remove it than keep support for older processors, because
live migrating guest partitions to newer processors may not be possible
if SAO is in use (or worse allowed with silent races).

- PROT_SAO stays in the uapi header so code using it would still build.
- arch_validate_prot() is removed, the generic version rejects PROT_SAO
  so applications would get a failure at mmap() time.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Drop KVM change for the time being]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200703011958.1166620-3-npiggin@gmail.com

tools/testing/selftests/powerpc/mm/.gitignore

@@ -2,7 +2,6 @@
 hugetlb_vs_thp_test
 subpage_prot
 tempfile
-prot_sao
 segv_errors
 wild_bctr
 large_vm_fork_separation

tools/testing/selftests/powerpc/mm/Makefile

@@ -2,7 +2,7 @@
 noarg:
 	$(MAKE) -C ../
 
-TEST_GEN_PROGS := hugetlb_vs_thp_test subpage_prot prot_sao segv_errors wild_bctr \
+TEST_GEN_PROGS := hugetlb_vs_thp_test subpage_prot segv_errors wild_bctr \
 		  large_vm_fork_separation bad_accesses pkey_exec_prot
 TEST_GEN_PROGS_EXTENDED := tlbie_test
 TEST_GEN_FILES := tempfile
@@ -12,8 +12,6 @@ include ../../lib.mk
 
 $(TEST_GEN_PROGS): ../harness.c ../utils.c
 
-$(OUTPUT)/prot_sao: ../utils.c
-
 $(OUTPUT)/wild_bctr: CFLAGS += -m64
 $(OUTPUT)/large_vm_fork_separation: CFLAGS += -m64
 $(OUTPUT)/bad_accesses: CFLAGS += -m64

tools/testing/selftests/powerpc/mm/prot_sao.c

@@ -1,42 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * Copyright 2016, Michael Ellerman, IBM Corp.
- */
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <sys/mman.h>
-
-#include <asm/cputable.h>
-
-#include "utils.h"
-
-#define SIZE (64 * 1024)
-
-int test_prot_sao(void)
-{
-	char *p;
-
-	/* 2.06 or later should support SAO */
-	SKIP_IF(!have_hwcap(PPC_FEATURE_ARCH_2_06));
-
-	/*
-	 * Ensure we can ask for PROT_SAO.
-	 * We can't really verify that it does the right thing, but at least we
-	 * confirm the kernel will accept it.
-	 */
-	p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE | PROT_SAO,
-		 MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
-	FAIL_IF(p == MAP_FAILED);
-
-	/* Write to the mapping, to at least cause a fault */
-	memset(p, 0xaa, SIZE);
-
-	return 0;
-}
-
-int main(void)
-{
-	return test_harness(test_prot_sao, "prot-sao");
-}