Re: [kvm-unit-tests PATCH v1 4/4] s390x: edat test

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On 09/02/2021 15.38, Claudio Imbrenda wrote:
Simple EDAT test.

Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
---
  s390x/Makefile      |   1 +
  s390x/edat.c        | 238 ++++++++++++++++++++++++++++++++++++++++++++
  s390x/unittests.cfg |   3 +
  3 files changed, 242 insertions(+)
  create mode 100644 s390x/edat.c

diff --git a/s390x/Makefile b/s390x/Makefile
index 08d85c9f..fc885150 100644
--- a/s390x/Makefile
+++ b/s390x/Makefile
@@ -20,6 +20,7 @@ tests += $(TEST_DIR)/sclp.elf
  tests += $(TEST_DIR)/css.elf
  tests += $(TEST_DIR)/uv-guest.elf
  tests += $(TEST_DIR)/sie.elf
+tests += $(TEST_DIR)/edat.elf
tests_binary = $(patsubst %.elf,%.bin,$(tests))
  ifneq ($(HOST_KEY_DOCUMENT),)
diff --git a/s390x/edat.c b/s390x/edat.c
new file mode 100644
index 00000000..504a1501
--- /dev/null
+++ b/s390x/edat.c
@@ -0,0 +1,238 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * EDAT test.
+ *
+ * Copyright (c) 2021 IBM Corp
+ *
+ * Authors:
+ *	Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
+ */
+#include <libcflat.h>
+#include <vmalloc.h>
+#include <asm/facility.h>
+#include <asm/interrupt.h>
+#include <mmu.h>
+#include <asm/pgtable.h>
+#include <asm-generic/barrier.h>
+
+#define TEID_ADDR	PAGE_MASK
+#define TEID_AI		0x003
+#define TEID_M		0x004
+#define TEID_A		0x008
+#define TEID_FS		0xc00
+
+#define LC_SIZE	(2 * PAGE_SIZE)
+#define VIRT(x)	((void *)((unsigned long)(x) + (unsigned long)mem))
+
+static uint8_t prefix_buf[LC_SIZE] __attribute__((aligned(LC_SIZE)));
+static unsigned int tmp[1024] __attribute__((aligned(PAGE_SIZE)));
+static void *root, *mem, *m;
+static struct lowcore *lc;
+volatile unsigned int *p;
+
+/* Expect a program interrupt, and clear the TEID */
+static void expect_dat_fault(void)
+{
+	expect_pgm_int();
+	lc->trans_exc_id = 0;
+}
+
+/* Check if a protection exception happened for the given address */
+static bool check_pgm_prot(void *ptr)
+{
+	unsigned long teid = lc->trans_exc_id;
+
+	if (lc->pgm_int_code != PGM_INT_CODE_PROTECTION)
+		return 0;

return false.
It's a bool return type.

+	if (~teid & TEID_M)

I'd maybe rather write this as:

        if (!(teid & TEID_M))

... but it's just a matter of taste.

+		return 1;

                return true;

So this is for backward compatiblity with older Z systems that do not have the corresponding facility? Should there be a corresponding facility check somewhere? Or maybe add at least a comment?

+	return (~teid & TEID_A) &&
+		((teid & TEID_ADDR) == ((uint64_t)ptr & PAGE_MASK)) &&
+		!(teid & TEID_AI);

So you're checking for one specific type of protection exception here only ... please add an appropriate comment.

+}
+
+static void test_dat(void)
+{
+	report_prefix_push("edat off");
+	/* disable EDAT */
+	ctl_clear_bit(0, 23);
+
+	/* Check some basics */
+	p[0] = 42;
+	report(p[0] == 42, "pte, r/w");
+	p[0] = 0;
+
+	protect_page(m, PAGE_ENTRY_P);
+	expect_dat_fault();
+	p[0] = 42;
+	unprotect_page(m, PAGE_ENTRY_P);
+	report(!p[0] && check_pgm_prot(m), "pte, ro");
+
+	/* The FC bit should be ignored because EDAT is off */
+	p[0] = 42;

I'd suggest to set p[0] = 0 here...

+	protect_dat_entry(m, SEGMENT_ENTRY_FC, 4);

... and change the value to 42 after enabling the protection ... otherwise you don't really test the non-working write protection here, do you?

+	report(p[0] == 42, "pmd, fc=1, r/w");
+	unprotect_dat_entry(m, SEGMENT_ENTRY_FC, 4);
+	p[0] = 0;
+
+	/* Segment protection should work even with EDAT off */
+	protect_dat_entry(m, SEGMENT_ENTRY_P, 4);
+	expect_dat_fault();
+	p[0] = 42;
+	report(!p[0] && check_pgm_prot(m), "pmd, ro");
+	unprotect_dat_entry(m, SEGMENT_ENTRY_P, 4);
+
+	/* The FC bit should be ignored because EDAT is off*/

Set p[0] to 0 again before enabling the protection? Or maybe use a different value than 42 below...?

+	protect_dat_entry(m, REGION3_ENTRY_FC, 3);
+	p[0] = 42;
+	report(p[0] == 42, "pud, fc=1, r/w");
+	unprotect_dat_entry(m, REGION3_ENTRY_FC, 3);
+	p[0] = 0;
+
+	/* Region1/2/3 protection should not work, because EDAT is off */
+	protect_dat_entry(m, REGION_ENTRY_P, 3);
+	p[0] = 42;
+	report(p[0] == 42, "pud, ro");
+	unprotect_dat_entry(m, REGION_ENTRY_P, 3);
+	p[0] = 0;
+
+	protect_dat_entry(m, REGION_ENTRY_P, 2);
+	p[0] = 42;
+	report(p[0] == 42, "p4d, ro");
+	unprotect_dat_entry(m, REGION_ENTRY_P, 2);
+	p[0] = 0;
+
+	protect_dat_entry(m, REGION_ENTRY_P, 1);
+	p[0] = 42;
+	report(p[0] == 42, "pgd, ro");
+	unprotect_dat_entry(m, REGION_ENTRY_P, 1);
+	p[0] = 0;
+
+	report_prefix_pop();
+}

 Thomas




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