Re: [kvm-unit-tests PATCH v4 4/6] s390x: Add library functions for exiting from snippet

Nico Boehr
2024-12-10T10:20:27Z

On Wed Oct 16, 2024 at 8:03 PM CEST, Nina Schoetterl-Glausch wrote:
> It is useful to be able to force an exit to the host from the snippet,
> as well as do so while returning a value.
> Add this functionality, also add helper functions for the host to check
> for an exit and get or check the value.
> Use diag 0x44 and 0x9c for this.
> Add a guest specific snippet header file and rename snippet.h to reflect
> that it is host specific.
>
> Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>

Hi Nina,

would you mind if I fix this up like this?

(copy-pasted so whitespace damage ahead)

diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
index 2dec7924..03adcd3c 100644
--- a/lib/s390x/asm/arch_def.h
+++ b/lib/s390x/asm/arch_def.h
@@ -510,11 +510,14 @@ static inline void diag44(void)
asm volatile("diag 0,0,0x44\n");
}

-static inline void diag9c(uint64_t val)
+static inline void diag500(uint64_t val)
{
- asm volatile("diag %[val],0,0x9c\n"
+ asm volatile(
+ "lgr 2,%[val]\n"
+ "diag 0,0,0x500\n"
:
: [val] "d"(val)
+ : "r2"
);
}

diff --git a/lib/s390x/snippet-exit.h b/lib/s390x/snippet-exit.h
index f62f0068..3ed4c22c 100644
--- a/lib/s390x/snippet-exit.h
+++ b/lib/s390x/snippet-exit.h
@@ -19,16 +19,14 @@ static inline bool snippet_is_force_exit(struct vm *vm)

static inline bool snippet_is_force_exit_value(struct vm *vm)
{
- return sie_is_diag_icpt(vm, 0x9c);
+ return sie_is_diag_icpt(vm, 0x500);
}

static inline uint64_t snippet_get_force_exit_value(struct vm *vm)
{
- struct kvm_s390_sie_block *sblk = vm->sblk;
-
assert(snippet_is_force_exit_value(vm));

- return vm->save_area.guest.grs[sblk_ip_as_diag(sblk).r_1];
+ return vm->save_area.guest.grs[2];
}

static inline void snippet_check_force_exit_value(struct vm *vm, uint64_t value_exp)
diff --git a/s390x/snippets/lib/snippet-exit.h b/s390x/snippets/lib/snippet-exit.h
index 0b483366..ac00de3f 100644
--- a/s390x/snippets/lib/snippet-exit.h
+++ b/s390x/snippets/lib/snippet-exit.h
@@ -21,7 +21,7 @@ static inline void force_exit(void)
static inline void force_exit_value(uint64_t val)
{
mb(); /* host may read any memory written by the guest before */
- diag9c(val);
+ diag500(val);
mb(); /* allow host to modify guest memory */
}