Re: [kvm-unit-tests PATCH v3 5/7] s390x: Add library functions for exiting from snippet

["Nicholas Piggin" <npiggin@gmail.com>]

On Fri Jun 21, 2024 at 12:16 AM AEST, 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>
> ---
>  s390x/Makefile                          |  1 +
>  lib/s390x/asm/arch_def.h                | 13 ++++++++
>  lib/s390x/snippet-guest.h               | 26 +++++++++++++++
>  lib/s390x/{snippet.h => snippet-host.h} | 10 ++++--
>  lib/s390x/snippet-host.c                | 42 +++++++++++++++++++++++++
>  lib/s390x/uv.c                          |  2 +-
>  s390x/mvpg-sie.c                        |  2 +-
>  s390x/pv-diags.c                        |  2 +-
>  s390x/pv-icptcode.c                     |  2 +-
>  s390x/pv-ipl.c                          |  2 +-
>  s390x/sie-dat.c                         |  2 +-
>  s390x/spec_ex-sie.c                     |  2 +-
>  s390x/uv-host.c                         |  2 +-
>  13 files changed, 97 insertions(+), 11 deletions(-)
>  create mode 100644 lib/s390x/snippet-guest.h
>  rename lib/s390x/{snippet.h => snippet-host.h} (92%)
>  create mode 100644 lib/s390x/snippet-host.c
>
> diff --git a/s390x/Makefile b/s390x/Makefile
> index 23342bd6..12445fb5 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -111,6 +111,7 @@ cflatobjs += lib/s390x/css_lib.o
>  cflatobjs += lib/s390x/malloc_io.o
>  cflatobjs += lib/s390x/uv.o
>  cflatobjs += lib/s390x/sie.o
> +cflatobjs += lib/s390x/snippet-host.o
>  cflatobjs += lib/s390x/fault.o
>  
>  OBJDIRS += lib/s390x
> diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
> index 745a3387..db04deca 100644
> --- a/lib/s390x/asm/arch_def.h
> +++ b/lib/s390x/asm/arch_def.h
> @@ -504,4 +504,17 @@ static inline uint32_t get_prefix(void)
>  	return current_prefix;
>  }
>  
> +static inline void diag44(void)
> +{
> +	asm volatile("diag	0,0,0x44\n");
> +}
> +
> +static inline void diag9c(uint64_t val)
> +{
> +	asm volatile("diag	%[val],0,0x9c\n"
> +		:
> +		: [val] "d"(val)
> +	);
> +}
> +
>  #endif
> diff --git a/lib/s390x/snippet-guest.h b/lib/s390x/snippet-guest.h
> new file mode 100644
> index 00000000..3cc098e1
> --- /dev/null
> +++ b/lib/s390x/snippet-guest.h
> @@ -0,0 +1,26 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Snippet functionality for the guest.
> + *
> + * Copyright IBM Corp. 2023
> + */
> +
> +#ifndef _S390X_SNIPPET_GUEST_H_
> +#define _S390X_SNIPPET_GUEST_H_
> +
> +#include <asm/arch_def.h>
> +#include <asm/barrier.h>
> +
> +static inline void force_exit(void)
> +{
> +	diag44();
> +	mb(); /* allow host to modify guest memory */
> +}
> +
> +static inline void force_exit_value(uint64_t val)
> +{
> +	diag9c(val);
> +	mb(); /* allow host to modify guest memory */
> +}
> +
> +#endif /* _S390X_SNIPPET_GUEST_H_ */
> diff --git a/lib/s390x/snippet.h b/lib/s390x/snippet-host.h
> similarity index 92%
> rename from lib/s390x/snippet.h
> rename to lib/s390x/snippet-host.h
> index 910849aa..230b25b0 100644
> --- a/lib/s390x/snippet.h
> +++ b/lib/s390x/snippet-host.h
> @@ -1,13 +1,13 @@
>  /* SPDX-License-Identifier: GPL-2.0-only */
>  /*
> - * Snippet definitions
> + * Snippet functionality for the host.
>   *
>   * Copyright IBM Corp. 2021
>   * Author: Janosch Frank <frankja@linux.ibm.com>
>   */
>  
> -#ifndef _S390X_SNIPPET_H_
> -#define _S390X_SNIPPET_H_
> +#ifndef _S390X_SNIPPET_HOST_H_
> +#define _S390X_SNIPPET_HOST_H_
>  
>  #include <sie.h>
>  #include <uv.h>
> @@ -144,4 +144,8 @@ static inline void snippet_setup_guest(struct vm *vm, bool is_pv)
>  	}
>  }
>  
> +bool snippet_is_force_exit(struct vm *vm);
> +bool snippet_is_force_exit_value(struct vm *vm);
> +uint64_t snippet_get_force_exit_value(struct vm *vm);
> +void snippet_check_force_exit_value(struct vm *vm, uint64_t exit_exp);
>  #endif
> diff --git a/lib/s390x/snippet-host.c b/lib/s390x/snippet-host.c
> new file mode 100644
> index 00000000..44a60bb9
> --- /dev/null
> +++ b/lib/s390x/snippet-host.c
> @@ -0,0 +1,42 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Snippet functionality for the host.
> + *
> + * Copyright IBM Corp. 2023
> + */
> +
> +#include <libcflat.h>
> +#include <snippet-host.h>
> +#include <sie.h>
> +
> +bool snippet_is_force_exit(struct vm *vm)
> +{
> +	return sie_is_diag_icpt(vm, 0x44);
> +}
> +
> +bool snippet_is_force_exit_value(struct vm *vm)
> +{
> +	return sie_is_diag_icpt(vm, 0x9c);
> +}
> +
> +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->ipa & 0xf0) >> 4];

Hmm, you have a nice instr struct that you made earlier and now you're
back to mask and shift... What about exposing that struct and add a
function to create it so you could do grs[sblk_to_instr(sblk).r1]
here... Just a thought.

Thanks,
Nick