Re: [kvm-unit-tests PATCH] s390x: Add diag308 subcode 0 testing

David Hildenbrand
2019-08-23T11:00:04Z

On 22.08.19 13:11, Janosch Frank wrote:
> By adding a load reset routine to cstart.S we can also test the clear
> reset done by subcode 0, as we now can restore our registers again.
>
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
> I managed to extract this from another bigger test, so let's add it to the bunch.
> I'd be very happy about assembly review :-)
> ---
> s390x/cstart64.S | 27 +++++++++++++++++++++++++++
> s390x/diag308.c | 31 ++++++++++---------------------
> 2 files changed, 37 insertions(+), 21 deletions(-)
>
> diff --git a/s390x/cstart64.S b/s390x/cstart64.S
> index dedfe80..47045e1 100644
> --- a/s390x/cstart64.S
> +++ b/s390x/cstart64.S
> @@ -145,6 +145,33 @@ memsetxc:
> .endm
>
> .section .text
> +/*
> + * load_reset calling convention:
> + * %r2 subcode (0 or 1)
> + */
> +.globl load_reset
> +load_reset:
> + SAVE_REGS
> + /* Save the first PSW word to the IPL PSW */
> + epsw %r0, %r1
> + st %r0, 0
> + /* Store the address and the bit for 31 bit addressing */
> + larl %r0, 0f
> + oilh %r0, 0x8000
> + st %r0, 0x4
> + /* Do the reset */
> + diag %r0,%r2,0x308
> + /* Failure path */
> + xgr %r2, %r2
> + br %r14
> + /* Success path */
> + /* We lost cr0 due to the reset */
> +0: larl %r1, initial_cr0
> + lctlg %c0, %c0, 0(%r1)
> + RESTORE_REGS
> + lhi %r2, 1
> + br %r14
> +
> pgm_int:
> SAVE_REGS
> brasl %r14, handle_pgm_int
> diff --git a/s390x/diag308.c b/s390x/diag308.c
> index f085b1a..baf9fd3 100644
> --- a/s390x/diag308.c
> +++ b/s390x/diag308.c
> @@ -21,32 +21,20 @@ static void test_priv(void)
> check_pgm_int_code(PGM_INT_CODE_PRIVILEGED_OPERATION);
> }
>
> +
> /*
> - * Check that diag308 with subcode 1 loads the PSW at address 0, i.e.
> + * Check that diag308 with subcode 0 and 1 loads the PSW at address 0, i.e.
> * that we can put a pointer into address 4 which then gets executed.
> */
> +extern int load_reset(u64);
> +static void test_subcode0(void)
> +{
> + report("load modified clear done", load_reset(0));
> +}
> +
> static void test_subcode1(void)
> {
> - uint64_t saved_psw = *(uint64_t *)0;
> - long subcode = 1;
> - long ret, tmp;
> -
> - asm volatile (
> - " epsw %0,%1\n"
> - " st %0,0\n"
> - " larl %0,0f\n"
> - " oilh %0,0x8000\n"
> - " st %0,4\n"
> - " diag 0,%2,0x308\n"
> - " lghi %0,0\n"
> - " j 1f\n"
> - "0: lghi %0,1\n"
> - "1:"
> - : "=&d"(ret), "=&d"(tmp) : "d"(subcode) : "memory");
> -
> - *(uint64_t *)0 = saved_psw;
> -
> - report("load normal reset done", ret == 1);
> + report("load normal reset done", load_reset(1));
> }
>
> /* Expect a specification exception when using an uneven register */
> @@ -107,6 +95,7 @@ static struct {
> void (*func)(void);
> } tests[] = {
> { "privileged", test_priv },
> + { "subcode 0", test_subcode0 },
> { "subcode 1", test_subcode1 },
> { "subcode 5", test_subcode5 },
> { "subcode 6", test_subcode6 },
>

So, in general I am wondering if we should restore the original IPL_PSW
after we used it - is there any chance we might require the old value
again (I guess we're fine with cpu resets)?

--

Thanks,

David / dhildenb