[kvm-unit-tests PATCH v3 0/3] s390x: mvpg test

[kvm-unit-tests PATCH v3 0/3] s390x: mvpg test

[Claudio Imbrenda]

A simple unit test for the MVPG instruction.

The timeout is set to 10 seconds because the test should complete in a
fraction of a second even on busy machines. If the test is run in VSIE
and the host of the host is not handling MVPG properly, the test will
probably hang.

Testing MVPG behaviour in VSIE is the main motivation for this test.

Anything related to storage keys is not tested.

v2->v3
* fix copyright (2020 is over!)
* add the third patch to skip some known issues when running in TCG

v1->v2
* droppped patch 2 which introduced is_pgm();
* patch 1: replace a hardcoded value with the new macro SVC_LEAVE_PSTATE
* patch 2: clear_pgm_int() returns the old value, use that instad of is_pgm()

Claudio Imbrenda (3):
  s390x: introduce leave_pstate to leave userspace
  s390x: mvpg: simple test
  s390x: mvpg: skip some tests when using TCG

 s390x/Makefile           |   1 +
 lib/s390x/asm/arch_def.h |   7 +
 lib/s390x/interrupt.c    |  12 +-
 s390x/mvpg.c             | 273 +++++++++++++++++++++++++++++++++++++++
 s390x/unittests.cfg      |   4 +
 5 files changed, 295 insertions(+), 2 deletions(-)
 create mode 100644 s390x/mvpg.c

-- 
2.26.2

[kvm-unit-tests PATCH v3 1/3] s390x: introduce leave_pstate to leave userspace

[Claudio Imbrenda]

In most testcases, we enter problem state (userspace) just to test if a
privileged instruction causes a fault. In some cases, though, we need
to test if an instruction works properly in userspace. This means that
we do not expect a fault, and we need an orderly way to leave problem
state afterwards.

This patch introduces a simple system based on the SVC instruction.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
---
 lib/s390x/asm/arch_def.h |  7 +++++++
 lib/s390x/interrupt.c    | 12 ++++++++++--
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
index 9c4e330a..4cf8eb11 100644
--- a/lib/s390x/asm/arch_def.h
+++ b/lib/s390x/asm/arch_def.h
@@ -173,6 +173,8 @@ struct cpuid {
 	uint64_t reserved : 15;
 };
 
+#define SVC_LEAVE_PSTATE 1
+
 static inline unsigned short stap(void)
 {
 	unsigned short cpu_address;
@@ -276,6 +278,11 @@ static inline void enter_pstate(void)
 	load_psw_mask(mask);
 }
 
+static inline void leave_pstate(void)
+{
+	asm volatile("	svc %0\n" : : "i" (SVC_LEAVE_PSTATE));
+}
+
 static inline int stsi(void *addr, int fc, int sel1, int sel2)
 {
 	register int r0 asm("0") = (fc << 28) | sel1;
diff --git a/lib/s390x/interrupt.c b/lib/s390x/interrupt.c
index 1ce36073..d0567845 100644
--- a/lib/s390x/interrupt.c
+++ b/lib/s390x/interrupt.c
@@ -188,6 +188,14 @@ int unregister_io_int_func(void (*f)(void))
 
 void handle_svc_int(void)
 {
-	report_abort("Unexpected supervisor call interrupt: on cpu %d at %#lx",
-		     stap(), lc->svc_old_psw.addr);
+	uint16_t code = lc->svc_int_code;
+
+	switch (code) {
+	case SVC_LEAVE_PSTATE:
+		lc->svc_old_psw.mask &= ~PSW_MASK_PSTATE;
+		break;
+	default:
+		report_abort("Unexpected supervisor call interrupt: code %#x on cpu %d at %#lx",
+			      code, stap(), lc->svc_old_psw.addr);
+	}
 }
-- 
2.26.2

[kvm-unit-tests PATCH v3 2/3] s390x: mvpg: simple test

[Claudio Imbrenda]

A simple unit test for the MVPG instruction.

The timeout is set to 10 seconds because the test should complete in a
fraction of a second even on busy machines. If the test is run in VSIE
and the host of the host is not handling MVPG properly, the test will
probably hang.

Testing MVPG behaviour in VSIE is the main motivation for this test.

Anything related to storage keys is not tested.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
---
 s390x/Makefile      |   1 +
 s390x/mvpg.c        | 266 ++++++++++++++++++++++++++++++++++++++++++++
 s390x/unittests.cfg |   4 +
 3 files changed, 271 insertions(+)
 create mode 100644 s390x/mvpg.c

diff --git a/s390x/Makefile b/s390x/Makefile
index 08d85c9f..770eaa0b 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)/mvpg.elf
 
 tests_binary = $(patsubst %.elf,%.bin,$(tests))
 ifneq ($(HOST_KEY_DOCUMENT),)
diff --git a/s390x/mvpg.c b/s390x/mvpg.c
new file mode 100644
index 00000000..792052ad
--- /dev/null
+++ b/s390x/mvpg.c
@@ -0,0 +1,266 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Move Page instruction tests
+ *
+ * Copyright (c) 2021 IBM Corp
+ *
+ * Authors:
+ *  Claudio Imbrenda <imbrenda@linux.ibm.com>
+ */
+#include <libcflat.h>
+#include <asm/asm-offsets.h>
+#include <asm-generic/barrier.h>
+#include <asm/interrupt.h>
+#include <asm/pgtable.h>
+#include <mmu.h>
+#include <asm/page.h>
+#include <asm/facility.h>
+#include <asm/mem.h>
+#include <asm/sigp.h>
+#include <smp.h>
+#include <alloc_page.h>
+#include <bitops.h>
+
+/* Used to build the appropriate test values for register 0 */
+#define KFC(x) ((x) << 10)
+#define CCO 0x100
+
+/* How much memory to allocate for the test */
+#define MEM_ORDER 12
+/* How many iterations to perform in the loops */
+#define ITER 8
+
+/* Used to generate the simple pattern */
+#define MAGIC 42
+
+static uint8_t source[PAGE_SIZE]  __attribute__((aligned(PAGE_SIZE)));
+static uint8_t buffer[PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
+
+/* Keep track of fresh memory */
+static uint8_t *fresh;
+
+static inline int mvpg(unsigned long r0, void *dest, void *src)
+{
+	register unsigned long reg0 asm ("0") = r0;
+	int cc;
+
+	asm volatile("	mvpg    %1,%2\n"
+		     "	ipm     %0\n"
+		     "	srl     %0,28"
+		: "=&d" (cc) : "a" (dest), "a" (src), "d" (reg0)
+		: "memory", "cc");
+	return cc;
+}
+
+/*
+ * Initialize a page with a simple pattern
+ */
+static void init_page(uint8_t *p)
+{
+	int i;
+
+	for (i = 0; i < PAGE_SIZE; i++)
+		p[i] = i + MAGIC;
+}
+
+/*
+ * Check if the given page contains the simple pattern
+ */
+static int page_ok(const uint8_t *p)
+{
+	int i;
+
+	for (i = 0; i < PAGE_SIZE; i++)
+		if (p[i] != (uint8_t)(i + MAGIC))
+			return 0;
+	return 1;
+}
+
+static void test_exceptions(void)
+{
+	int i, expected;
+
+	report_prefix_push("exceptions");
+
+	/*
+	 * Key Function Control values 4 and 5 are allowed only in supervisor
+	 * state, and even then, only if the move-page-and-set-key facility
+	 * is present (STFLE bit 149)
+	 */
+	report_prefix_push("privileged");
+	if (test_facility(149)) {
+		expected = PGM_INT_CODE_PRIVILEGED_OPERATION;
+		for (i = 4; i < 6; i++) {
+			expect_pgm_int();
+			enter_pstate();
+			mvpg(KFC(i), buffer, source);
+			report(clear_pgm_int() == expected, "Key Function Control value %d", i);
+		}
+	} else {
+		report_skip("Key Function Control value %d", 4);
+		report_skip("Key Function Control value %d", 5);
+		i = 4;
+	}
+	report_prefix_pop();
+
+	/*
+	 * Invalid values of the Key Function Control, or setting the
+	 * reserved bits, should result in a specification exception
+	 */
+	report_prefix_push("specification");
+	expected = PGM_INT_CODE_SPECIFICATION;
+	expect_pgm_int();
+	mvpg(KFC(3), buffer, source);
+	report(clear_pgm_int() == expected, "Key Function Control value 3");
+	for (; i < 32; i++) {
+		expect_pgm_int();
+		mvpg(KFC(i), buffer, source);
+		report(clear_pgm_int() == expected, "Key Function Control value %d", i);
+	}
+	report_prefix_pop();
+
+	/* Operands outside memory result in addressing exceptions, as usual */
+	report_prefix_push("addressing");
+	expected = PGM_INT_CODE_ADDRESSING;
+	expect_pgm_int();
+	mvpg(0, buffer, (void *)PAGE_MASK);
+	report(clear_pgm_int() == expected, "Second operand outside memory");
+
+	expect_pgm_int();
+	mvpg(0, (void *)PAGE_MASK, source);
+	report(clear_pgm_int() == expected, "First operand outside memory");
+	report_prefix_pop();
+
+	report_prefix_pop();
+}
+
+static void test_success(void)
+{
+	int cc;
+
+	report_prefix_push("success");
+	/* Test successful scenarios, both in supervisor and problem state */
+	cc = mvpg(0, buffer, source);
+	report(page_ok(buffer) && !cc, "Supervisor state MVPG successful");
+
+	enter_pstate();
+	cc = mvpg(0, buffer, source);
+	leave_pstate();
+	report(page_ok(buffer) && !cc, "Problem state MVPG successful");
+
+	report_prefix_pop();
+}
+
+static void test_small_loop(const void *string)
+{
+	uint8_t *dest;
+	int i, cc;
+
+	/* Looping over cold and warm pages helps catch VSIE bugs */
+	report_prefix_push(string);
+	dest = fresh;
+	for (i = 0; i < ITER; i++) {
+		cc = mvpg(0, fresh, source);
+		report(page_ok(fresh) && !cc, "cold: %p, %p", source, fresh);
+		fresh += PAGE_SIZE;
+	}
+
+	for (i = 0; i < ITER; i++) {
+		memset(dest, 0, PAGE_SIZE);
+		cc = mvpg(0, dest, source);
+		report(page_ok(dest) && !cc, "warm: %p, %p", source, dest);
+		dest += PAGE_SIZE;
+	}
+	report_prefix_pop();
+}
+
+static void test_mmu_prot(void)
+{
+	int cc;
+
+	report_prefix_push("protection");
+	report_prefix_push("cco=0");
+
+	/* MVPG should still succeed when the source is read-only */
+	protect_page(source, PAGE_ENTRY_P);
+	cc = mvpg(0, fresh, source);
+	report(page_ok(fresh) && !cc, "source read only");
+	unprotect_page(source, PAGE_ENTRY_P);
+	fresh += PAGE_SIZE;
+
+	/*
+	 * When the source or destination are invalid, a page translation
+	 * exception should be raised; when the destination is read-only,
+	 * a protection exception should be raised.
+	 */
+	protect_page(fresh, PAGE_ENTRY_P);
+	expect_pgm_int();
+	mvpg(0, fresh, source);
+	report(clear_pgm_int() == PGM_INT_CODE_PROTECTION, "destination read only");
+	fresh += PAGE_SIZE;
+
+	protect_page(source, PAGE_ENTRY_I);
+	expect_pgm_int();
+	mvpg(0, fresh, source);
+	report(clear_pgm_int() == PGM_INT_CODE_PAGE_TRANSLATION, "source invalid");
+	unprotect_page(source, PAGE_ENTRY_I);
+	fresh += PAGE_SIZE;
+
+	protect_page(fresh, PAGE_ENTRY_I);
+	expect_pgm_int();
+	mvpg(0, fresh, source);
+	report(clear_pgm_int() == PGM_INT_CODE_PAGE_TRANSLATION, "destination invalid");
+	fresh += PAGE_SIZE;
+
+	report_prefix_pop();
+	report_prefix_push("cco=1");
+	/*
+	 * Setting the CCO bit should suppress page translation exceptions,
+	 * but not protection exceptions.
+	 */
+	protect_page(fresh, PAGE_ENTRY_P);
+	expect_pgm_int();
+	mvpg(CCO, fresh, source);
+	report(clear_pgm_int() == PGM_INT_CODE_PROTECTION, "destination read only");
+	fresh += PAGE_SIZE;
+
+	protect_page(fresh, PAGE_ENTRY_I);
+	cc = mvpg(CCO, fresh, source);
+	report(cc == 1, "destination invalid");
+	fresh += PAGE_SIZE;
+
+	protect_page(source, PAGE_ENTRY_I);
+	cc = mvpg(CCO, fresh, source);
+	report(cc == 2, "source invalid");
+	fresh += PAGE_SIZE;
+
+	protect_page(fresh, PAGE_ENTRY_I);
+	cc = mvpg(CCO, fresh, source);
+	report(cc == 2, "source and destination invalid");
+	fresh += PAGE_SIZE;
+
+	unprotect_page(source, PAGE_ENTRY_I);
+	report_prefix_pop();
+	report_prefix_pop();
+}
+
+int main(void)
+{
+	report_prefix_push("mvpg");
+
+	init_page(source);
+	fresh = alloc_pages_flags(MEM_ORDER, FLAG_DONTZERO | FLAG_FRESH);
+	assert(fresh);
+
+	test_exceptions();
+	test_success();
+	test_small_loop("nommu");
+
+	setup_vm();
+
+	test_small_loop("mmu");
+	test_mmu_prot();
+
+	report_prefix_pop();
+	return report_summary();
+}
diff --git a/s390x/unittests.cfg b/s390x/unittests.cfg
index 2298be6c..9f81a608 100644
--- a/s390x/unittests.cfg
+++ b/s390x/unittests.cfg
@@ -99,3 +99,7 @@ file = uv-guest.elf
 
 [sie]
 file = sie.elf
+
+[mvpg]
+file = mvpg.elf
+timeout = 10
-- 
2.26.2

[kvm-unit-tests PATCH v3 3/3] s390x: mvpg: skip some tests when using TCG

[Claudio Imbrenda]

TCG is known to fail these tests, so add an explicit exception to skip them.

Once TCG has been fixed, it will be enough to revert this patch.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 s390x/mvpg.c | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/s390x/mvpg.c b/s390x/mvpg.c
index 792052ad..148095e0 100644
--- a/s390x/mvpg.c
+++ b/s390x/mvpg.c
@@ -20,6 +20,7 @@
 #include <smp.h>
 #include <alloc_page.h>
 #include <bitops.h>
+#include <vm.h>
 
 /* Used to build the appropriate test values for register 0 */
 #define KFC(x) ((x) << 10)
@@ -224,20 +225,26 @@ static void test_mmu_prot(void)
 	report(clear_pgm_int() == PGM_INT_CODE_PROTECTION, "destination read only");
 	fresh += PAGE_SIZE;
 
-	protect_page(fresh, PAGE_ENTRY_I);
-	cc = mvpg(CCO, fresh, source);
-	report(cc == 1, "destination invalid");
-	fresh += PAGE_SIZE;
+	if (vm_is_tcg()) {
+		report_skip("destination invalid");
+		report_skip("source invalid");
+		report_skip("source and destination invalid");
+	} else {
+		protect_page(fresh, PAGE_ENTRY_I);
+		cc = mvpg(CCO, fresh, source);
+		report(cc == 1, "destination invalid");
+		fresh += PAGE_SIZE;
 
-	protect_page(source, PAGE_ENTRY_I);
-	cc = mvpg(CCO, fresh, source);
-	report(cc == 2, "source invalid");
-	fresh += PAGE_SIZE;
+		protect_page(source, PAGE_ENTRY_I);
+		cc = mvpg(CCO, fresh, source);
+		report(cc == 2, "source invalid");
+		fresh += PAGE_SIZE;
 
-	protect_page(fresh, PAGE_ENTRY_I);
-	cc = mvpg(CCO, fresh, source);
-	report(cc == 2, "source and destination invalid");
-	fresh += PAGE_SIZE;
+		protect_page(fresh, PAGE_ENTRY_I);
+		cc = mvpg(CCO, fresh, source);
+		report(cc == 2, "source and destination invalid");
+		fresh += PAGE_SIZE;
+	}
 
 	unprotect_page(source, PAGE_ENTRY_I);
 	report_prefix_pop();
-- 
2.26.2

Re: [kvm-unit-tests PATCH v3 1/3] s390x: introduce leave_pstate to leave userspace

[Thomas Huth]

On 01/03/2021 19.28, Claudio Imbrenda wrote:
> In most testcases, we enter problem state (userspace) just to test if a
> privileged instruction causes a fault. In some cases, though, we need
> to test if an instruction works properly in userspace. This means that
> we do not expect a fault, and we need an orderly way to leave problem
> state afterwards.
> 
> This patch introduces a simple system based on the SVC instruction.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Acked-by: David Hildenbrand <david@redhat.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
> ---
>   lib/s390x/asm/arch_def.h |  7 +++++++
>   lib/s390x/interrupt.c    | 12 ++++++++++--
>   2 files changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
> index 9c4e330a..4cf8eb11 100644
> --- a/lib/s390x/asm/arch_def.h
> +++ b/lib/s390x/asm/arch_def.h
> @@ -173,6 +173,8 @@ struct cpuid {
>   	uint64_t reserved : 15;
>   };
>   
> +#define SVC_LEAVE_PSTATE 1
> +
>   static inline unsigned short stap(void)
>   {
>   	unsigned short cpu_address;
> @@ -276,6 +278,11 @@ static inline void enter_pstate(void)
>   	load_psw_mask(mask);
>   }
>   
> +static inline void leave_pstate(void)
> +{
> +	asm volatile("	svc %0\n" : : "i" (SVC_LEAVE_PSTATE));
> +}
> +
>   static inline int stsi(void *addr, int fc, int sel1, int sel2)
>   {
>   	register int r0 asm("0") = (fc << 28) | sel1;
> diff --git a/lib/s390x/interrupt.c b/lib/s390x/interrupt.c
> index 1ce36073..d0567845 100644
> --- a/lib/s390x/interrupt.c
> +++ b/lib/s390x/interrupt.c
> @@ -188,6 +188,14 @@ int unregister_io_int_func(void (*f)(void))
>   
>   void handle_svc_int(void)
>   {
> -	report_abort("Unexpected supervisor call interrupt: on cpu %d at %#lx",
> -		     stap(), lc->svc_old_psw.addr);
> +	uint16_t code = lc->svc_int_code;
> +
> +	switch (code) {
> +	case SVC_LEAVE_PSTATE:
> +		lc->svc_old_psw.mask &= ~PSW_MASK_PSTATE;
> +		break;
> +	default:
> +		report_abort("Unexpected supervisor call interrupt: code %#x on cpu %d at %#lx",
> +			      code, stap(), lc->svc_old_psw.addr);
> +	}
>   }
> 

Reviewed-by: Thomas Huth <thuth@redhat.com>

Re: [kvm-unit-tests PATCH v3 2/3] s390x: mvpg: simple test

[Thomas Huth]

On 01/03/2021 19.28, Claudio Imbrenda wrote:
> A simple unit test for the MVPG instruction.
> 
> The timeout is set to 10 seconds because the test should complete in a
> fraction of a second even on busy machines. If the test is run in VSIE
> and the host of the host is not handling MVPG properly, the test will
> probably hang.
> 
> Testing MVPG behaviour in VSIE is the main motivation for this test.
> 
> Anything related to storage keys is not tested.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Acked-by: Janosch Frank <frankja@linux.ibm.com>
> ---
[...]
> +static void test_success(void)
> +{
> +	int cc;
> +
> +	report_prefix_push("success");
> +	/* Test successful scenarios, both in supervisor and problem state */
> +	cc = mvpg(0, buffer, source);
> +	report(page_ok(buffer) && !cc, "Supervisor state MVPG successful");

I'd maybe add a memset(buffer, 0xff, PAGE_SIZE) here to make sure that the 
buffer really gets re-written before the next page_ok() check.

> +	enter_pstate();
> +	cc = mvpg(0, buffer, source);
> +	leave_pstate();
> +	report(page_ok(buffer) && !cc, "Problem state MVPG successful");
> +
> +	report_prefix_pop();
> +}

Anyway:
Reviewed-by: Thomas Huth <thuth@redhat.com>

Re: [kvm-unit-tests PATCH v3 3/3] s390x: mvpg: skip some tests when using TCG

[Thomas Huth]

On 01/03/2021 19.28, Claudio Imbrenda wrote:
> TCG is known to fail these tests, so add an explicit exception to skip them.
> 
> Once TCG has been fixed, it will be enough to revert this patch.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
>   s390x/mvpg.c | 31 +++++++++++++++++++------------
>   1 file changed, 19 insertions(+), 12 deletions(-)
> 
> diff --git a/s390x/mvpg.c b/s390x/mvpg.c
> index 792052ad..148095e0 100644
> --- a/s390x/mvpg.c
> +++ b/s390x/mvpg.c
> @@ -20,6 +20,7 @@
>   #include <smp.h>
>   #include <alloc_page.h>
>   #include <bitops.h>
> +#include <vm.h>
>   
>   /* Used to build the appropriate test values for register 0 */
>   #define KFC(x) ((x) << 10)
> @@ -224,20 +225,26 @@ static void test_mmu_prot(void)
>   	report(clear_pgm_int() == PGM_INT_CODE_PROTECTION, "destination read only");
>   	fresh += PAGE_SIZE;
>   
> -	protect_page(fresh, PAGE_ENTRY_I);
> -	cc = mvpg(CCO, fresh, source);
> -	report(cc == 1, "destination invalid");
> -	fresh += PAGE_SIZE;
> +	if (vm_is_tcg()) {
> +		report_skip("destination invalid");
> +		report_skip("source invalid");
> +		report_skip("source and destination invalid");

You could also use report_xfail(vm_is_tcg(), ...) instead. That shows that 
there are still problems without failing CI runs.

Anyway:
Reviewed-by: Thomas Huth <thuth@redhat.com>

Re: [kvm-unit-tests PATCH v3 3/3] s390x: mvpg: skip some tests when using TCG

[Janosch Frank]

On 3/2/21 6:59 AM, Thomas Huth wrote:
> On 01/03/2021 19.28, Claudio Imbrenda wrote:
>> TCG is known to fail these tests, so add an explicit exception to skip them.
>>
>> Once TCG has been fixed, it will be enough to revert this patch.
>>
>> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
>> ---
>>   s390x/mvpg.c | 31 +++++++++++++++++++------------
>>   1 file changed, 19 insertions(+), 12 deletions(-)
>>
>> diff --git a/s390x/mvpg.c b/s390x/mvpg.c
>> index 792052ad..148095e0 100644
>> --- a/s390x/mvpg.c
>> +++ b/s390x/mvpg.c
>> @@ -20,6 +20,7 @@
>>   #include <smp.h>
>>   #include <alloc_page.h>
>>   #include <bitops.h>
>> +#include <vm.h>
>>   
>>   /* Used to build the appropriate test values for register 0 */
>>   #define KFC(x) ((x) << 10)
>> @@ -224,20 +225,26 @@ static void test_mmu_prot(void)
>>   	report(clear_pgm_int() == PGM_INT_CODE_PROTECTION, "destination read only");
>>   	fresh += PAGE_SIZE;
>>   
>> -	protect_page(fresh, PAGE_ENTRY_I);
>> -	cc = mvpg(CCO, fresh, source);
>> -	report(cc == 1, "destination invalid");
>> -	fresh += PAGE_SIZE;
>> +	if (vm_is_tcg()) {
>> +		report_skip("destination invalid");
>> +		report_skip("source invalid");
>> +		report_skip("source and destination invalid");
> 
> You could also use report_xfail(vm_is_tcg(), ...) instead. That shows that 
> there are still problems without failing CI runs.

If I remember correctly we fail with a PGM so we would also need to add
a expect_pgm_int() call before each test when running under tcg
therefore it's not just a 1:1 replacement in this case.

But yes, I'd also like an indication why we're skipping. A comment and a
TCG prefix for skips should be enough.


> 
> Anyway:
> Reviewed-by: Thomas Huth <thuth@redhat.com>
>