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

[Janosch Frank <frankja@linux.ibm.com>]

On 10/13/21 12:35, Claudio Imbrenda wrote:
> 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))
> 

Will do

>> +
>> +/*
>> + * 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.

Sure, for the ASM snippets the entry address only depends on where you 
copy them if I'm not mistaken.

> 
> 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;
>