Re: [kvm-unit-tests PATCH v4] s390x: Test effect of storage keys on some instructions

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On Mon, 25 Apr 2022 10:41:28 +0200
Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx> wrote:

> Some instructions are emulated by KVM. Test that KVM correctly emulates
> storage key checking for two of those instructions (STORE CPU ADDRESS,
> SET PREFIX).
> Test success and error conditions, including coverage of storage and
> fetch protection override.
> Also add test for TEST PROTECTION, even if that instruction will not be
> emulated by KVM under normal conditions.
> 
> Signed-off-by: Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx>
> ---
> Range-diff against v3:
> 1:  dc4ae46f ! 1:  a9af3e08 s390x: Test effect of storage keys on some instructions
>     @@ s390x/skey.c: static void test_invalid_address(void)
>      +static void store_cpu_address_key_1(uint16_t *out)
>      +{
>      +	asm volatile (
>     -+		"spka 0x10(0)\n\t"
>     -+		"stap %0\n\t"
>     -+		"spka 0(0)\n"
>     ++		"spka	0x10\n\t"
>     ++		"stap	%0\n\t"
>     ++		"spka	0\n"
>      +	     : "+Q" (*out) /* exception: old value remains in out -> + constraint */
>      +	);
>      +}
>     @@ s390x/skey.c: static void test_invalid_address(void)
>      + * Perform SET PREFIX (SPX) instruction while temporarily executing
>      + * with access key 1.
>      + */
>     -+static void set_prefix_key_1(uint32_t *out)
>     ++static void set_prefix_key_1(uint32_t *prefix_ptr)
>      +{
>      +	asm volatile (
>     -+		"spka 0x10(0)\n\t"
>     ++		"spka	0x10\n\t"
>      +		"spx	%0\n\t"
>     -+		"spka 0(0)\n"
>     -+	     :: "Q" (*out)
>     ++		"spka	0\n"
>     ++	     :: "Q" (*prefix_ptr)
>      +	);
>      +}
>      +
>     @@ s390x/skey.c: static void test_invalid_address(void)
>      +
>      +static void test_set_prefix(void)
>      +{
>     -+	uint32_t *out = (uint32_t *)pagebuf;
>     ++	char lowcore_tmp[PAGE_SIZE * 2] __attribute__((aligned(PAGE_SIZE * 2)));
>     ++	uint32_t *prefix_ptr = (uint32_t *)pagebuf;
>     ++	uint32_t old_prefix;
>      +	pgd_t *root;
>      +
>      +	report_prefix_push("SET PREFIX");
>      +	root = (pgd_t *)(stctg(1) & PAGE_MASK);
>     -+
>     -+	asm volatile("stpx	%0" : "=Q"(*out));
>     ++	old_prefix = get_prefix();
>     ++	memcpy(lowcore_tmp, 0, PAGE_SIZE * 2);
>     ++	assert(((uint64_t)&lowcore_tmp >> 31) == 0);
>     ++	*prefix_ptr = (uint32_t)(uint64_t)&lowcore_tmp;
>      +
>      +	report_prefix_push("zero key");
>     -+	set_storage_key(pagebuf, 0x20, 0);
>     -+	asm volatile("spx	%0" :: "Q" (*out));
>     -+	report_pass("no exception");
>     ++	set_prefix(old_prefix);
>     ++	set_storage_key(prefix_ptr, 0x20, 0);
>     ++	set_prefix(*prefix_ptr);
>     ++	report(get_prefix() == *prefix_ptr, "set prefix");
>      +	report_prefix_pop();
>      +
>      +	report_prefix_push("matching key");
>     ++	set_prefix(old_prefix);
>      +	set_storage_key(pagebuf, 0x10, 0);
>     -+	set_prefix_key_1(out);
>     -+	report_pass("no exception");
>     ++	set_prefix_key_1(prefix_ptr);
>     ++	report(get_prefix() == *prefix_ptr, "set prefix");
>      +	report_prefix_pop();
>      +
>     -+	report_prefix_push("mismatching key, no fetch protection");
>     ++	report_prefix_push("mismatching key");
>     ++
>     ++	report_prefix_push("no fetch protection");
>     ++	set_prefix(old_prefix);
>      +	set_storage_key(pagebuf, 0x20, 0);
>     -+	set_prefix_key_1(out);
>     -+	report_pass("no exception");
>     ++	set_prefix_key_1(prefix_ptr);
>     ++	report(get_prefix() == *prefix_ptr, "set prefix");
>      +	report_prefix_pop();
>      +
>     -+	report_prefix_push("mismatching key, fetch protection");
>     ++	report_prefix_push("fetch protection");
>     ++	set_prefix(old_prefix);
>      +	set_storage_key(pagebuf, 0x28, 0);
>      +	expect_pgm_int();
>     -+	*out = 0xdeadbeef;
>     -+	set_prefix_key_1(out);
>     ++	set_prefix_key_1(prefix_ptr);
>      +	check_pgm_int_code(PGM_INT_CODE_PROTECTION);
>     -+	asm volatile("stpx	%0" : "=Q"(*out));
>     -+	report(*out != 0xdeadbeef, "no fetch occurred");
>     ++	report(get_prefix() != *prefix_ptr, "did not set prefix");
>      +	report_prefix_pop();
>      +
>      +	register_pgm_cleanup_func(dat_fixup_pgm_int);
>      +
>     -+	report_prefix_push("mismatching key, remapped page, fetch protection");
>     ++	report_prefix_push("remapped page, fetch protection");
>     ++	set_prefix(old_prefix);
>      +	set_storage_key(pagebuf, 0x28, 0);
>      +	expect_pgm_int();
>     -+	WRITE_ONCE(*out, 0xdeadbeef);
>      +	install_page(root, virt_to_pte_phys(root, pagebuf), 0);
>      +	set_prefix_key_1((uint32_t *)0);
>      +	install_page(root, 0, 0);
>      +	check_pgm_int_code(PGM_INT_CODE_PROTECTION);
>     -+	asm volatile("stpx	%0" : "=Q"(*out));
>     -+	report(*out != 0xdeadbeef, "no fetch occurred");
>     ++	report(get_prefix() != *prefix_ptr, "did not set prefix");
>      +	report_prefix_pop();
>      +
>      +	ctl_set_bit(0, CTL0_FETCH_PROTECTION_OVERRIDE);
>      +
>     -+	report_prefix_push("mismatching key, fetch protection override applies");
>     ++	report_prefix_push("fetch protection override applies");
>     ++	set_prefix(old_prefix);
>      +	set_storage_key(pagebuf, 0x28, 0);
>      +	install_page(root, virt_to_pte_phys(root, pagebuf), 0);
>      +	set_prefix_key_1((uint32_t *)0);
>      +	install_page(root, 0, 0);
>     -+	report_pass("no exception");
>     ++	report(get_prefix() == *prefix_ptr, "set prefix");
>      +	report_prefix_pop();
>      +
>     -+	report_prefix_push("mismatching key, fetch protection override does not apply");
>     -+	out = (uint32_t *)(pagebuf + 2048);
>     -+	set_storage_key(pagebuf, 0x28, 0);
>     -+	expect_pgm_int();
>     -+	WRITE_ONCE(*out, 0xdeadbeef);
>     -+	install_page(root, virt_to_pte_phys(root, pagebuf), 0);
>     -+	set_prefix_key_1((uint32_t *)2048);
>     -+	install_page(root, 0, 0);
>     -+	check_pgm_int_code(PGM_INT_CODE_PROTECTION);
>     -+	asm volatile("stpx	%0" : "=Q"(*out));
>     -+	report(*out != 0xdeadbeef, "no fetch occurred");
>     -+	report_prefix_pop();
>     ++	{
>     ++		uint32_t *prefix_ptr = (uint32_t *)(pagebuf + 2048);
>     ++
>     ++		WRITE_ONCE(*prefix_ptr, (uint32_t)(uint64_t)&lowcore_tmp);
>     ++		report_prefix_push("fetch protection override does not apply");
>     ++		set_prefix(old_prefix);
>     ++		set_storage_key(pagebuf, 0x28, 0);
>     ++		expect_pgm_int();
>     ++		install_page(root, virt_to_pte_phys(root, pagebuf), 0);
>     ++		set_prefix_key_1((uint32_t *)2048);
>     ++		install_page(root, 0, 0);
>     ++		check_pgm_int_code(PGM_INT_CODE_PROTECTION);
>     ++		report(get_prefix() != *prefix_ptr, "did not set prefix");
>     ++		report_prefix_pop();
>     ++	}
>      +
>      +	ctl_clear_bit(0, CTL0_FETCH_PROTECTION_OVERRIDE);
>     -+	set_storage_key(pagebuf, 0x00, 0);
>      +	register_pgm_cleanup_func(NULL);
>      +	report_prefix_pop();
>     ++	set_storage_key(pagebuf, 0x00, 0);
>     ++	report_prefix_pop();
>      +}
>      +
>       int main(void)
> 
>  lib/s390x/asm/arch_def.h |  20 ++--
>  s390x/skey.c             | 227 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 238 insertions(+), 9 deletions(-)
> 
> diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
> index bab3c374..676a2753 100644
> --- a/lib/s390x/asm/arch_def.h
> +++ b/lib/s390x/asm/arch_def.h
> @@ -55,15 +55,17 @@ struct psw {
>  #define PSW_MASK_BA			0x0000000080000000UL
>  #define PSW_MASK_64			(PSW_MASK_BA | PSW_MASK_EA)
>  
> -#define CTL0_LOW_ADDR_PROT		(63 - 35)
> -#define CTL0_EDAT			(63 - 40)
> -#define CTL0_IEP			(63 - 43)
> -#define CTL0_AFP			(63 - 45)
> -#define CTL0_VECTOR			(63 - 46)
> -#define CTL0_EMERGENCY_SIGNAL		(63 - 49)
> -#define CTL0_EXTERNAL_CALL		(63 - 50)
> -#define CTL0_CLOCK_COMPARATOR		(63 - 52)
> -#define CTL0_SERVICE_SIGNAL		(63 - 54)
> +#define CTL0_LOW_ADDR_PROT			(63 - 35)
> +#define CTL0_EDAT				(63 - 40)
> +#define CTL0_FETCH_PROTECTION_OVERRIDE		(63 - 38)
> +#define CTL0_STORAGE_PROTECTION_OVERRIDE	(63 - 39)
> +#define CTL0_IEP				(63 - 43)
> +#define CTL0_AFP				(63 - 45)
> +#define CTL0_VECTOR				(63 - 46)
> +#define CTL0_EMERGENCY_SIGNAL			(63 - 49)
> +#define CTL0_EXTERNAL_CALL			(63 - 50)
> +#define CTL0_CLOCK_COMPARATOR			(63 - 52)
> +#define CTL0_SERVICE_SIGNAL			(63 - 54)
>  #define CR0_EXTM_MASK			0x0000000000006200UL /* Combined external masks */
>  
>  #define CTL2_GUARDED_STORAGE		(63 - 59)
> diff --git a/s390x/skey.c b/s390x/skey.c
> index edad53e9..aa2b845f 100644
> --- a/s390x/skey.c
> +++ b/s390x/skey.c
> @@ -10,6 +10,7 @@
>  #include <libcflat.h>
>  #include <asm/asm-offsets.h>
>  #include <asm/interrupt.h>
> +#include <vmalloc.h>
>  #include <asm/page.h>
>  #include <asm/facility.h>
>  #include <asm/mem.h>
> @@ -118,6 +119,227 @@ static void test_invalid_address(void)
>  	report_prefix_pop();
>  }
>  
> +static void test_test_protection(void)
> +{
> +	unsigned long addr = (unsigned long)pagebuf;
> +
> +	report_prefix_push("TPROT");
> +
> +	set_storage_key(pagebuf, 0x10, 0);
> +	report(tprot(addr, 0) == 0, "access key 0 -> no protection");
> +	report(tprot(addr, 1) == 0, "access key matches -> no protection");
> +	report(tprot(addr, 2) == 1, "access key mismatches, no fetch protection -> store protection");
> +
> +	set_storage_key(pagebuf, 0x18, 0);
> +	report(tprot(addr, 2) == 2, "access key mismatches, fetch protection -> fetch & store protection");
> +
> +	ctl_set_bit(0, CTL0_STORAGE_PROTECTION_OVERRIDE);
> +	set_storage_key(pagebuf, 0x90, 0);
> +	report(tprot(addr, 2) == 0, "access key mismatches, storage protection override -> no protection");
> +	ctl_clear_bit(0, CTL0_STORAGE_PROTECTION_OVERRIDE);
> +
> +	set_storage_key(pagebuf, 0x00, 0);
> +	report_prefix_pop();
> +}
> +
> +/*
> + * Perform STORE CPU ADDRESS (STAP) instruction while temporarily executing
> + * with access key 1.
> + */
> +static void store_cpu_address_key_1(uint16_t *out)
> +{
> +	asm volatile (
> +		"spka	0x10\n\t"
> +		"stap	%0\n\t"
> +		"spka	0\n"
> +	     : "+Q" (*out) /* exception: old value remains in out -> + constraint */
> +	);
> +}
> +
> +static void test_store_cpu_address(void)
> +{
> +	uint16_t *out = (uint16_t *)pagebuf;
> +	uint16_t cpu_addr;
> +
> +	report_prefix_push("STORE CPU ADDRESS");
> +	asm ("stap %0" : "=Q" (cpu_addr));
> +
> +	report_prefix_push("zero key");
> +	set_storage_key(pagebuf, 0x20, 0);
> +	WRITE_ONCE(*out, 0xbeef);
> +	asm ("stap %0" : "=Q" (*out));
> +	report(*out == cpu_addr, "store occurred");
> +	report_prefix_pop();
> +
> +	report_prefix_push("matching key");
> +	set_storage_key(pagebuf, 0x10, 0);
> +	*out = 0xbeef;
> +	store_cpu_address_key_1(out);
> +	report(*out == cpu_addr, "store occurred");
> +	report_prefix_pop();
> +
> +	report_prefix_push("mismatching key");
> +	set_storage_key(pagebuf, 0x20, 0);
> +	expect_pgm_int();
> +	*out = 0xbeef;
> +	store_cpu_address_key_1(out);
> +	check_pgm_int_code(PGM_INT_CODE_PROTECTION);
> +	report(*out == 0xbeef, "no store occurred");
> +	report_prefix_pop();
> +
> +	ctl_set_bit(0, CTL0_STORAGE_PROTECTION_OVERRIDE);
> +
> +	report_prefix_push("storage-protection override, invalid key");
> +	set_storage_key(pagebuf, 0x20, 0);
> +	expect_pgm_int();
> +	*out = 0xbeef;
> +	store_cpu_address_key_1(out);
> +	check_pgm_int_code(PGM_INT_CODE_PROTECTION);
> +	report(*out == 0xbeef, "no store occurred");
> +	report_prefix_pop();
> +
> +	report_prefix_push("storage-protection override, override key");
> +	set_storage_key(pagebuf, 0x90, 0);
> +	*out = 0xbeef;
> +	store_cpu_address_key_1(out);
> +	report(*out == cpu_addr, "override occurred");
> +	report_prefix_pop();
> +
> +	ctl_clear_bit(0, CTL0_STORAGE_PROTECTION_OVERRIDE);
> +
> +	report_prefix_push("storage-protection override disabled, override key");
> +	set_storage_key(pagebuf, 0x90, 0);
> +	expect_pgm_int();
> +	*out = 0xbeef;
> +	store_cpu_address_key_1(out);
> +	check_pgm_int_code(PGM_INT_CODE_PROTECTION);
> +	report(*out == 0xbeef, "no store occurred");
> +	report_prefix_pop();
> +
> +	set_storage_key(pagebuf, 0x00, 0);
> +	report_prefix_pop();
> +}
> +
> +/*
> + * Perform SET PREFIX (SPX) instruction while temporarily executing
> + * with access key 1.
> + */
> +static void set_prefix_key_1(uint32_t *prefix_ptr)
> +{
> +	asm volatile (
> +		"spka	0x10\n\t"
> +		"spx	%0\n\t"
> +		"spka	0\n"
> +	     :: "Q" (*prefix_ptr)
> +	);
> +}
> +
> +/*
> + * We remapped page 0, making the lowcore inaccessible, which breaks the normal
> + * handler and breaks skipping the faulting instruction.
> + * Just disable dynamic address translation to make things work.
> + */
> +static void dat_fixup_pgm_int(void)
> +{
> +	uint64_t psw_mask = extract_psw_mask();
> +
> +	psw_mask &= ~PSW_MASK_DAT;
> +	load_psw_mask(psw_mask);
> +}
> +
> +static void test_set_prefix(void)
> +{
> +	char lowcore_tmp[PAGE_SIZE * 2] __attribute__((aligned(PAGE_SIZE * 2)));

perhaps it's cleaner to put this as a global (static) variable

also, please define LC_SIZE (2*PAGE_SIZE) and use that

> +	uint32_t *prefix_ptr = (uint32_t *)pagebuf;
> +	uint32_t old_prefix;
> +	pgd_t *root;
> +
> +	report_prefix_push("SET PREFIX");
> +	root = (pgd_t *)(stctg(1) & PAGE_MASK);
> +	old_prefix = get_prefix();
> +	memcpy(lowcore_tmp, 0, PAGE_SIZE * 2);
> +	assert(((uint64_t)&lowcore_tmp >> 31) == 0);
> +	*prefix_ptr = (uint32_t)(uint64_t)&lowcore_tmp;
> +
> +	report_prefix_push("zero key");
> +	set_prefix(old_prefix);
> +	set_storage_key(prefix_ptr, 0x20, 0);
> +	set_prefix(*prefix_ptr);
> +	report(get_prefix() == *prefix_ptr, "set prefix");
> +	report_prefix_pop();
> +
> +	report_prefix_push("matching key");
> +	set_prefix(old_prefix);
> +	set_storage_key(pagebuf, 0x10, 0);
> +	set_prefix_key_1(prefix_ptr);
> +	report(get_prefix() == *prefix_ptr, "set prefix");
> +	report_prefix_pop();
> +
> +	report_prefix_push("mismatching key");
> +
> +	report_prefix_push("no fetch protection");
> +	set_prefix(old_prefix);
> +	set_storage_key(pagebuf, 0x20, 0);
> +	set_prefix_key_1(prefix_ptr);
> +	report(get_prefix() == *prefix_ptr, "set prefix");
> +	report_prefix_pop();
> +
> +	report_prefix_push("fetch protection");
> +	set_prefix(old_prefix);
> +	set_storage_key(pagebuf, 0x28, 0);
> +	expect_pgm_int();
> +	set_prefix_key_1(prefix_ptr);
> +	check_pgm_int_code(PGM_INT_CODE_PROTECTION);
> +	report(get_prefix() != *prefix_ptr, "did not set prefix");

why don't you check == old_prefix instead? that way you know noting has
changed (also for all the other tests below where you do the same)

> +	report_prefix_pop();
> +
> +	register_pgm_cleanup_func(dat_fixup_pgm_int);
> +
> +	report_prefix_push("remapped page, fetch protection");
> +	set_prefix(old_prefix);
> +	set_storage_key(pagebuf, 0x28, 0);
> +	expect_pgm_int();
> +	install_page(root, virt_to_pte_phys(root, pagebuf), 0);
> +	set_prefix_key_1((uint32_t *)0);
> +	install_page(root, 0, 0);
> +	check_pgm_int_code(PGM_INT_CODE_PROTECTION);
> +	report(get_prefix() != *prefix_ptr, "did not set prefix");
> +	report_prefix_pop();
> +
> +	ctl_set_bit(0, CTL0_FETCH_PROTECTION_OVERRIDE);
> +
> +	report_prefix_push("fetch protection override applies");
> +	set_prefix(old_prefix);
> +	set_storage_key(pagebuf, 0x28, 0);
> +	install_page(root, virt_to_pte_phys(root, pagebuf), 0);
> +	set_prefix_key_1((uint32_t *)0);
> +	install_page(root, 0, 0);
> +	report(get_prefix() == *prefix_ptr, "set prefix");
> +	report_prefix_pop();
> +
> +	{
> +		uint32_t *prefix_ptr = (uint32_t *)(pagebuf + 2048);

please don't alias variables

either reuse the existing one (and restore its value once you are
done), or add a new variable for this purpose

> +
> +		WRITE_ONCE(*prefix_ptr, (uint32_t)(uint64_t)&lowcore_tmp);
> +		report_prefix_push("fetch protection override does not apply");
> +		set_prefix(old_prefix);
> +		set_storage_key(pagebuf, 0x28, 0);
> +		expect_pgm_int();
> +		install_page(root, virt_to_pte_phys(root, pagebuf), 0);
> +		set_prefix_key_1((uint32_t *)2048);
> +		install_page(root, 0, 0);
> +		check_pgm_int_code(PGM_INT_CODE_PROTECTION);
> +		report(get_prefix() != *prefix_ptr, "did not set prefix");
> +		report_prefix_pop();
> +	}
> +
> +	ctl_clear_bit(0, CTL0_FETCH_PROTECTION_OVERRIDE);
> +	register_pgm_cleanup_func(NULL);
> +	report_prefix_pop();
> +	set_storage_key(pagebuf, 0x00, 0);
> +	report_prefix_pop();
> +}
> +
>  int main(void)
>  {
>  	report_prefix_push("skey");
> @@ -130,6 +352,11 @@ int main(void)
>  	test_set();
>  	test_set_mb();
>  	test_chg();
> +	test_test_protection();
> +	test_store_cpu_address();
> +
> +	setup_vm();
> +	test_set_prefix();
>  done:
>  	report_prefix_pop();
>  	return report_summary();
> 
> base-commit: 6a7a83ed106211fc0ee530a3a05f171f6a4c4e66




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