Re: [kvm-unit-tests PATCH v6 2/3] s390x: Test effect of storage keys on some instructions

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Wed, 27 Apr 2022 12:06:10 +0200
Janis Schoetterl-Glausch <scgl@linux.ibm.com> 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@linux.ibm.com>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> Reviewed-by: Janosch Frank <frankja@linux.ibm.com>

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
>  lib/s390x/asm/arch_def.h |  20 ++--
>  s390x/skey.c             | 236 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 247 insertions(+), 9 deletions(-)
> 
> diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
> index 46c370e6..72553819 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..46efe3f5 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 +119,236 @@ 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) == TPROT_READ_WRITE, "access key 0 -> no protection");
> +	report(tprot(addr, 1) == TPROT_READ_WRITE, "access key matches -> no protection");
> +	report(tprot(addr, 2) == TPROT_READ,
> +	       "access key mismatches, no fetch protection -> store protection");
> +
> +	set_storage_key(pagebuf, 0x18, 0);
> +	report(tprot(addr, 2) == TPROT_RW_PROTECTED,
> +	       "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) == TPROT_READ_WRITE,
> +	       "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);
> +}
> +
> +#define PREFIX_AREA_SIZE (PAGE_SIZE * 2)
> +static char lowcore_tmp[PREFIX_AREA_SIZE] __attribute__((aligned(PREFIX_AREA_SIZE)));
> +
> +/*
> + * Test accessibility of the operand to SET PREFIX given different configurations
> + * with regards to storage keys. That is, check the accessibility of the location
> + * holding the new prefix, not that of the new prefix area. The new prefix area
> + * is a valid lowcore, so that the test does not crash on failure.
> + */
> +static void test_set_prefix(void)
> +{
> +	uint32_t *prefix_ptr = (uint32_t *)pagebuf;
> +	uint32_t *no_override_prefix_ptr;
> +	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, sizeof(lowcore_tmp));
> +	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() == old_prefix, "did not set prefix");
> +	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() == old_prefix, "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();
> +
> +	no_override_prefix_ptr = (uint32_t *)(pagebuf + 2048);
> +	WRITE_ONCE(*no_override_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() == old_prefix, "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 +361,11 @@ 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();