Re: [RFC PATCH v1 04/10] KVM: s390: selftests: Test TEST PROTECTION emulation

[Janosch Frank <frankja@linux.ibm.com>]

On 1/18/22 10:52, Janis Schoetterl-Glausch wrote:
> Test the emulation of TEST PROTECTION in the presence of storage keys.
> Emulation only occurs under certain conditions, one of which is the host
> page being protected.
> Trigger this by protecting the test pages via mprotect.
> 
> Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
> ---
>   tools/testing/selftests/kvm/.gitignore    |   1 +
>   tools/testing/selftests/kvm/Makefile      |   1 +
>   tools/testing/selftests/kvm/s390x/tprot.c | 184 ++++++++++++++++++++++
>   3 files changed, 186 insertions(+)
>   create mode 100644 tools/testing/selftests/kvm/s390x/tprot.c
> 
> diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
> index 3763105029fb..82c0470b6849 100644
> --- a/tools/testing/selftests/kvm/.gitignore
> +++ b/tools/testing/selftests/kvm/.gitignore
> @@ -7,6 +7,7 @@
>   /s390x/memop
>   /s390x/resets
>   /s390x/sync_regs_test
> +/s390x/tprot
>   /x86_64/cr4_cpuid_sync_test
>   /x86_64/debug_regs
>   /x86_64/evmcs_test
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index c4e34717826a..df6de8d155e8 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -109,6 +109,7 @@ TEST_GEN_PROGS_aarch64 += kvm_binary_stats_test
>   TEST_GEN_PROGS_s390x = s390x/memop
>   TEST_GEN_PROGS_s390x += s390x/resets
>   TEST_GEN_PROGS_s390x += s390x/sync_regs_test
> +TEST_GEN_PROGS_s390x += s390x/tprot
>   TEST_GEN_PROGS_s390x += demand_paging_test
>   TEST_GEN_PROGS_s390x += dirty_log_test
>   TEST_GEN_PROGS_s390x += kvm_create_max_vcpus
> diff --git a/tools/testing/selftests/kvm/s390x/tprot.c b/tools/testing/selftests/kvm/s390x/tprot.c
> new file mode 100644
> index 000000000000..8b52675307f6
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/s390x/tprot.c
> @@ -0,0 +1,184 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Test TEST PROTECTION emulation.
> + * In order for emulation occur the target page has to be DAT protected in the
> + * host mappings. Since the page tables are shared, we can use mprotect
> + * to achieve this.
> + *
> + * Copyright IBM Corp. 2021
> + */
> +
> +#include <sys/mman.h>
> +#include "test_util.h"
> +#include "kvm_util.h"
> +
> +#define PAGE_SHIFT 12
> +#define PAGE_SIZE (1 << PAGE_SHIFT)
> +#define CR0_FETCH_PROTECTION_OVERRIDE	(1UL << (63 - 38))
> +#define CR0_STORAGE_PROTECTION_OVERRIDE	(1UL << (63 - 39))
> +
> +#define VCPU_ID 1
> +
> +static __aligned(PAGE_SIZE) uint8_t pages[2][PAGE_SIZE];
> +static uint8_t *const page_store_prot = pages[0];
> +static uint8_t *const page_fetch_prot = pages[1];
> +
> +static int set_storage_key(void *addr, uint8_t key)
> +{
> +	int not_mapped = 0;
> +

Maybe add a short comment:
Check if address is mapped via lra and set the storage key if it is.

> +	asm volatile (
> +		       "lra	%[addr], 0(0,%[addr])\n"
> +		"	jz	0f\n"
> +		"	llill	%[not_mapped],1\n"
> +		"	j	1f\n"
> +		"0:	sske	%[key], %[addr]\n"
> +		"1:"
> +		: [addr] "+&a" (addr), [not_mapped] "+r" (not_mapped)

Shouldn't this be a "=r" instead of a "+r" for not_mapped?

> +		: [key] "r" (key)
> +		: "cc"
> +	);
> +	return -not_mapped;
> +}
> +
> +enum permission {
> +	READ_WRITE = 0,
> +	READ = 1,
> +	NONE = 2,
> +	UNAVAILABLE = 3,

TRANSLATION_NA ?
I'm not completely happy with these names but I've yet to come up with a 
better naming scheme here.

> +};
> +
> +static enum permission test_protection(void *addr, uint8_t key)
> +{
> +	uint64_t mask;
> +
> +	asm volatile (
> +		       "tprot	%[addr], 0(%[key])\n"
> +		"	ipm	%[mask]\n"
> +		: [mask] "=r" (mask)
> +		: [addr] "Q" (*(char *)addr),
> +		  [key] "a" (key)
> +		: "cc"
> +	);
> +
> +	return (enum permission)mask >> 28;

You could replace the shift with the "srl" that we normally do.

> +}
> +
> +enum stage {
> +	STAGE_END,
> +	STAGE_INIT_SIMPLE,
> +	TEST_SIMPLE,
> +	STAGE_INIT_FETCH_PROT_OVERRIDE,
> +	TEST_FETCH_PROT_OVERRIDE,
> +	TEST_STORAGE_PROT_OVERRIDE,
> +};
> +
> +struct test {
> +	enum stage stage;
> +	void *addr;
> +	uint8_t key;
> +	enum permission expected;
> +} tests[] = {
> +	/* Those which result in NONE/UNAVAILABLE will be interpreted by SIE,
> +	 * not KVM, but there is no harm in testing them also.
> +	 * See Enhanced Suppression-on-Protection Facilities in the
> +	 * Interpretive-Execution Mode
> +	 */

Outside of net/ we put the first line on "*" not on "/*"

s/Those which result in/Tests resulting in/ ?

> +	{ TEST_SIMPLE, page_store_prot, 0x00, READ_WRITE },
> +	{ TEST_SIMPLE, page_store_prot, 0x10, READ_WRITE },
> +	{ TEST_SIMPLE, page_store_prot, 0x20, READ },
> +	{ TEST_SIMPLE, page_fetch_prot, 0x00, READ_WRITE },
> +	{ TEST_SIMPLE, page_fetch_prot, 0x90, READ_WRITE },
> +	{ TEST_SIMPLE, page_fetch_prot, 0x10, NONE },
> +	{ TEST_SIMPLE, (void *)0x00, 0x10, UNAVAILABLE },
> +	/* Fetch-protection override */
> +	{ TEST_FETCH_PROT_OVERRIDE, (void *)0x00, 0x10, READ },
> +	{ TEST_FETCH_PROT_OVERRIDE, (void *)2049, 0x10, NONE },
> +	/* Storage-protection override */
> +	{ TEST_STORAGE_PROT_OVERRIDE, page_fetch_prot, 0x10, READ_WRITE },
> +	{ TEST_STORAGE_PROT_OVERRIDE, page_store_prot, 0x20, READ },
> +	{ TEST_STORAGE_PROT_OVERRIDE, (void *)2049, 0x10, READ_WRITE },
> +	/* End marker */
> +	{ STAGE_END, 0, 0, 0 },
> +};
> +
> +static enum stage perform_next_stage(int *i, bool mapped_0)
> +{
> +	enum stage stage = tests[*i].stage;
> +	enum permission result;
> +	bool skip;
> +
> +	for (; tests[*i].stage == stage; (*i)++) {
> +		skip = tests[*i].addr < (void *)4096 &&
> +		       !mapped_0 &&
> +		       tests[*i].expected != UNAVAILABLE;

Time for a comment?

> +		if (!skip) {
> +			result = test_protection(tests[*i].addr, tests[*i].key);
> +			GUEST_ASSERT_2(result == tests[*i].expected, *i, result);
> +		}
> +	}
> +	return stage;
> +}
> +
> +static void guest_code(void)
> +{
> +	bool mapped_0;
> +	int i = 0;
> +

It's __really__ hard to understand this since the state is changed both 
by the guest and host. Please add comments to this and maybe also add 
some to the test struct explaining why you expect the results for each test.

> +	GUEST_ASSERT_EQ(set_storage_key(page_store_prot, 0x10), 0);
> +	GUEST_ASSERT_EQ(set_storage_key(page_fetch_prot, 0x98), 0);
> +	GUEST_SYNC(STAGE_INIT_SIMPLE);
> +	GUEST_SYNC(perform_next_stage(&i, false));
> +
> +	/* Fetch-protection override */
> +	mapped_0 = !set_storage_key((void *)0, 0x98);
> +	GUEST_SYNC(STAGE_INIT_FETCH_PROT_OVERRIDE);
> +	GUEST_SYNC(perform_next_stage(&i, mapped_0));
> +
> +	/* Storage-protection override */
> +	GUEST_SYNC(perform_next_stage(&i, mapped_0));
> +}
> +
> +#define HOST_SYNC(vmp, stage)							\
> +({										\
> +	struct kvm_vm *__vm = (vmp);						\
> +	struct ucall uc;							\
> +	int __stage = (stage);							\
> +										\
> +	vcpu_run(__vm, VCPU_ID);						\
> +	get_ucall(__vm, VCPU_ID, &uc);						\
> +	if (uc.cmd == UCALL_ABORT) {						\
> +		TEST_FAIL("line %lu: %s, hints: %lu, %lu", uc.args[1],		\
> +			  (const char *)uc.args[0], uc.args[2], uc.args[3]);	\
> +	}									\
> +	ASSERT_EQ(uc.cmd, UCALL_SYNC);						\
> +	ASSERT_EQ(uc.args[1], __stage);						\
> +})
> +
> +int main(int argc, char *argv[])
> +{
> +	struct kvm_vm *vm;
> +	struct kvm_run *run;
> +	vm_vaddr_t guest_0_page;
> +
> +	vm = vm_create_default(VCPU_ID, 0, guest_code);
> +	run = vcpu_state(vm, VCPU_ID);
> +
> +	HOST_SYNC(vm, STAGE_INIT_SIMPLE);
> +	mprotect(addr_gva2hva(vm, (vm_vaddr_t)pages), PAGE_SIZE * 2, PROT_READ);
> +	HOST_SYNC(vm, TEST_SIMPLE);
> +
> +	guest_0_page = vm_vaddr_alloc(vm, PAGE_SIZE, 0);
> +	if (guest_0_page != 0)
> +		print_skip("Did not allocate page at 0 for fetch protection override tests");
> +	HOST_SYNC(vm, STAGE_INIT_FETCH_PROT_OVERRIDE);
> +	if (guest_0_page == 0)
> +		mprotect(addr_gva2hva(vm, (vm_vaddr_t)0), PAGE_SIZE, PROT_READ);
> +	run->s.regs.crs[0] |= CR0_FETCH_PROTECTION_OVERRIDE;
> +	run->kvm_dirty_regs = KVM_SYNC_CRS;
> +	HOST_SYNC(vm, TEST_FETCH_PROT_OVERRIDE);
> +
> +	run->s.regs.crs[0] |= CR0_STORAGE_PROTECTION_OVERRIDE;
> +	run->kvm_dirty_regs = KVM_SYNC_CRS;
> +	HOST_SYNC(vm, TEST_STORAGE_PROT_OVERRIDE);
> +}
>