Re: [kvm-unit-tests PATCH 2/2] lib: s390x: snippet.h: Add a few constants that will make our life easier

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

On Wed, 13 Oct 2021 10:27:22 +0000
Janosch Frank <frankja@linux.ibm.com> wrote:

> The variable names for the snippet objects are of gigantic length so
> let's define a few macros to make them easier to read.
> 
> Also add a standard PSW which should be used to start the snippet.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
>  lib/s390x/snippet.h | 40 ++++++++++++++++++++++++++++++++++++++++
>  s390x/mvpg-sie.c    | 13 ++++++-------
>  2 files changed, 46 insertions(+), 7 deletions(-)
>  create mode 100644 lib/s390x/snippet.h
> 
> diff --git a/lib/s390x/snippet.h b/lib/s390x/snippet.h
> new file mode 100644
> index 00000000..9ead4fe3
> --- /dev/null
> +++ b/lib/s390x/snippet.h
> @@ -0,0 +1,40 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Snippet definitions
> + *
> + * Copyright IBM, Corp. 2021
> + * Author: Janosch Frank <frankja@linux.ibm.com>
> + */
> +
> +#ifndef _S390X_SNIPPET_H_
> +#define _S390X_SNIPPET_H_
> +
> +/* This macro cuts down the length of the pointers to snippets */
> +#define SNIPPET_NAME_START(type, file) \
> +	_binary_s390x_snippets_##type##_##file##_gbin_start
> +#define SNIPPET_NAME_END(type, file) \
> +	_binary_s390x_snippets_##type##_##file##_gbin_end
> +
> +/* Returns the length of the snippet */
> +#define SNIPPET_LEN(type, file) \
> +	(uintptr_t)SNIPPET_NAME_END(type, file) - (uintptr_t)SNIPPET_NAME_START(type, file)

parentheses around the expansion:
	((uintptr_t)SNIPPET_NAME_END(type, file) - (uintptr_t)SNIPPET_NAME_START(type, file))

> +
> +/*
> + * C snippet instructions start at 0x4000 due to the prefix and the
> + * stack being before that.
> + */
> +#define SNIPPET_C_ENTRY_ADDR 0x4000
> +/* ASM snippets only have the prefix and hence start at 0x2000 */

wouldn't it be possible to make both start at the same address?
would make everything easier.

ASM snippets would have a couple of unused pages, but who cares?

> +#define SNIPPET_ASM_ENTRY_ADDR 0x2000
> +
> +/* Standard entry PSWs for snippets which can simply be copied into the guest PSW */
> +static const struct psw snippet_c_psw = {
> +	.mask = PSW_MASK_64,
> +	.addr = SNIPPET_C_ENTRY_ADDR,
> +};
> +
> +static const struct psw snippet_asm_psw = {
> +	.mask = PSW_MASK_64,
> +	.addr = SNIPPET_ASM_ENTRY_ADDR,
> +};
> +#endif
> diff --git a/s390x/mvpg-sie.c b/s390x/mvpg-sie.c
> index 5adcec1e..46170d02 100644
> --- a/s390x/mvpg-sie.c
> +++ b/s390x/mvpg-sie.c
> @@ -19,6 +19,7 @@
>  #include <vm.h>
>  #include <sclp.h>
>  #include <sie.h>
> +#include <snippet.h>
>  
>  static u8 *guest;
>  static struct vm vm;
> @@ -27,8 +28,8 @@ static uint8_t *src;
>  static uint8_t *dst;
>  static uint8_t *cmp;
>  
> -extern const char _binary_s390x_snippets_c_mvpg_snippet_gbin_start[];
> -extern const char _binary_s390x_snippets_c_mvpg_snippet_gbin_end[];
> +extern const char SNIPPET_NAME_START(c, mvpg_snippet)[];
> +extern const char SNIPPET_NAME_END(c, mvpg_snippet)[];
>  int binary_size;
>  
>  static void test_mvpg_pei(void)
> @@ -77,10 +78,9 @@ static void test_mvpg_pei(void)
>  
>  static void test_mvpg(void)
>  {
> -	int binary_size = ((uintptr_t)_binary_s390x_snippets_c_mvpg_snippet_gbin_end -
> -			   (uintptr_t)_binary_s390x_snippets_c_mvpg_snippet_gbin_start);
> +	int binary_size = SNIPPET_LEN(c, mvpg_snippet);
>  
> -	memcpy(guest, _binary_s390x_snippets_c_mvpg_snippet_gbin_start, binary_size);
> +	memcpy(guest, SNIPPET_NAME_START(c, mvpg_snippet), binary_size);
>  	memset(src, 0x42, PAGE_SIZE);
>  	memset(dst, 0x43, PAGE_SIZE);
>  	sie(&vm);
> @@ -96,8 +96,7 @@ static void setup_guest(void)
>  
>  	sie_guest_create(&vm, (uint64_t)guest, HPAGE_SIZE);
>  
> -	vm.sblk->gpsw.addr = PAGE_SIZE * 4;
> -	vm.sblk->gpsw.mask = PSW_MASK_64;
> +	vm.sblk->gpsw = snippet_c_psw;
>  	vm.sblk->ictl = ICTL_OPEREXC | ICTL_PINT;
>  	/* Enable MVPG interpretation as we want to test KVM and not ourselves */
>  	vm.sblk->eca = ECA_MVPGI;