Re: [kvm-unit-tests PATCH v3 2/8] s390x: Consolidate sclp read info

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

On 12/17/20 12:47 PM, Claudio Imbrenda wrote:
> On Fri, 11 Dec 2020 05:00:33 -0500
> Janosch Frank <frankja@linux.ibm.com> wrote:
> 
>> Let's only read the information once and pass a pointer to it instead
>> of calling sclp multiple times.
>>
>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>> ---
>>  lib/s390x/io.c   |  1 +
>>  lib/s390x/sclp.c | 31 +++++++++++++++++++++++++------
>>  lib/s390x/sclp.h |  3 +++
>>  lib/s390x/smp.c  | 27 +++++++++++----------------
>>  4 files changed, 40 insertions(+), 22 deletions(-)
>>
>> diff --git a/lib/s390x/io.c b/lib/s390x/io.c
>> index 1ff0589..6a1da63 100644
>> --- a/lib/s390x/io.c
>> +++ b/lib/s390x/io.c
>> @@ -34,6 +34,7 @@ void setup(void)
>>  {
>>  	setup_args_progname(ipl_args);
>>  	setup_facilities();
>> +	sclp_read_info();
>>  	sclp_console_setup();
>>  	sclp_memory_setup();
>>  	smp_setup();
>> diff --git a/lib/s390x/sclp.c b/lib/s390x/sclp.c
>> index 08a4813..bf1d9c0 100644
>> --- a/lib/s390x/sclp.c
>> +++ b/lib/s390x/sclp.c
>> @@ -23,6 +23,8 @@ extern unsigned long stacktop;
>>  static uint64_t storage_increment_size;
>>  static uint64_t max_ram_size;
>>  static uint64_t ram_size;
>> +char _read_info[PAGE_SIZE] __attribute__((__aligned__(4096)));
> 
> why not __aligned__((PAGE_SIZE)) ?

Because aligned is not defined as a compiler attribute in the lib AFAIK.
I can of course use PAGE_SIZE though.

> 
>> +static ReadInfo *read_info;
> 
> I wonder if a union would be cleaner? although later on you check if
> the pointer is NULL to see if the information is there, so I guess it
> can stay

I'm rather wondering if we want to replace that with an allocation,
these PAGE_SIZE arrays are just looking strange.

Let me put that on my TODO list for next year...

> 
>>  
>>  char _sccb[PAGE_SIZE] __attribute__((__aligned__(4096)));
>>  static volatile bool sclp_busy;
>> @@ -108,6 +110,24 @@ static void sclp_read_scp_info(ReadInfo *ri, int
>> length) report_abort("READ_SCP_INFO failed");
>>  }
>>  
>> +void sclp_read_info(void)
>> +{
>> +	sclp_read_scp_info((void *)_read_info, SCCB_SIZE);
>> +	read_info = (ReadInfo *)_read_info;
>> +}
>> +
>> +int sclp_get_cpu_num(void)
>> +{
>> +	assert(read_info);
>> +	return read_info->entries_cpu;
>> +}
>> +
>> +CPUEntry *sclp_get_cpu_entries(void)
>> +{
>> +	assert(read_info);
>> +	return (void *)read_info + read_info->offset_cpu;
> 
> are you doing arithmetic on a void pointer? please don't, it's ugly and
> against the specs. moreover you do have a char pointer...
> 
> why not:
> return (CPUEntry *)(_read_info + read_info->offset_cpu);

I seem to be one of those crazy persons who actually like void pointers.
Your suggestion looks good too, I'll replace my code with it.

> 
>> +}
>> +
>>  /* Perform service call. Return 0 on success, non-zero otherwise. */
>>  int sclp_service_call(unsigned int command, void *sccb)
>>  {
>> @@ -125,23 +145,22 @@ int sclp_service_call(unsigned int command,
>> void *sccb) 
>>  void sclp_memory_setup(void)
>>  {
>> -	ReadInfo *ri = (void *)_sccb;
>>  	uint64_t rnmax, rnsize;
>>  	int cc;
>>  
>> -	sclp_read_scp_info(ri, SCCB_SIZE);
>> +	assert(read_info);
>>  
>>  	/* calculate the storage increment size */
>> -	rnsize = ri->rnsize;
>> +	rnsize = read_info->rnsize;
>>  	if (!rnsize) {
>> -		rnsize = ri->rnsize2;
>> +		rnsize = read_info->rnsize2;
>>  	}
>>  	storage_increment_size = rnsize << 20;
>>  
>>  	/* calculate the maximum memory size */
>> -	rnmax = ri->rnmax;
>> +	rnmax = read_info->rnmax;
>>  	if (!rnmax) {
>> -		rnmax = ri->rnmax2;
>> +		rnmax = read_info->rnmax2;
>>  	}
>>  	max_ram_size = rnmax * storage_increment_size;
>>  
>> diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
>> index 9a6aad0..acd86d5 100644
>> --- a/lib/s390x/sclp.h
>> +++ b/lib/s390x/sclp.h
>> @@ -268,6 +268,9 @@ void sclp_wait_busy(void);
>>  void sclp_mark_busy(void);
>>  void sclp_console_setup(void);
>>  void sclp_print(const char *str);
>> +void sclp_read_info(void);
>> +int sclp_get_cpu_num(void);
>> +CPUEntry *sclp_get_cpu_entries(void);
>>  int sclp_service_call(unsigned int command, void *sccb);
>>  void sclp_memory_setup(void);
>>  uint64_t get_ram_size(void);
>> diff --git a/lib/s390x/smp.c b/lib/s390x/smp.c
>> index c4f02dc..dfcfd28 100644
>> --- a/lib/s390x/smp.c
>> +++ b/lib/s390x/smp.c
>> @@ -23,7 +23,6 @@
>>  #include "smp.h"
>>  #include "sclp.h"
>>  
>> -static char cpu_info_buffer[PAGE_SIZE]
>> __attribute__((__aligned__(4096))); static struct cpu *cpus;
>>  static struct cpu *cpu0;
>>  static struct spinlock lock;
>> @@ -32,8 +31,7 @@ extern void smp_cpu_setup_state(void);
>>  
>>  int smp_query_num_cpus(void)
>>  {
>> -	struct ReadCpuInfo *info = (void *)cpu_info_buffer;
>> -	return info->nr_configured;
>> +	return sclp_get_cpu_num();
>>  }
>>  
>>  struct cpu *smp_cpu_from_addr(uint16_t addr)
>> @@ -226,10 +224,10 @@ void smp_teardown(void)
>>  {
>>  	int i = 0;
>>  	uint16_t this_cpu = stap();
>> -	struct ReadCpuInfo *info = (void *)cpu_info_buffer;
>> +	int num = smp_query_num_cpus();
>>  
>>  	spin_lock(&lock);
>> -	for (; i < info->nr_configured; i++) {
>> +	for (; i < num; i++) {
>>  		if (cpus[i].active &&
>>  		    cpus[i].addr != this_cpu) {
>>  			sigp_retry(cpus[i].addr, SIGP_STOP, 0, NULL);
>> @@ -243,22 +241,19 @@ extern uint64_t *stackptr;
>>  void smp_setup(void)
>>  {
>>  	int i = 0;
>> +	int num = smp_query_num_cpus();
>>  	unsigned short cpu0_addr = stap();
>> -	struct ReadCpuInfo *info = (void *)cpu_info_buffer;
>> +	struct CPUEntry *entry = sclp_get_cpu_entries();
>>  
>>  	spin_lock(&lock);
>> -	sclp_mark_busy();
>> -	info->h.length = PAGE_SIZE;
>> -	sclp_service_call(SCLP_READ_CPU_INFO, cpu_info_buffer);
>> +	if (num > 1)
>> +		printf("SMP: Initializing, found %d cpus\n", num);
>>  
>> -	if (smp_query_num_cpus() > 1)
>> -		printf("SMP: Initializing, found %d cpus\n",
>> info->nr_configured); -
>> -	cpus = calloc(info->nr_configured, sizeof(cpus));
>> -	for (i = 0; i < info->nr_configured; i++) {
>> -		cpus[i].addr = info->entries[i].address;
>> +	cpus = calloc(num, sizeof(cpus));
>> +	for (i = 0; i < num; i++) {
>> +		cpus[i].addr = entry[i].address;
>>  		cpus[i].active = false;
>> -		if (info->entries[i].address == cpu0_addr) {
>> +		if (entry[i].address == cpu0_addr) {
>>  			cpu0 = &cpus[i];
>>  			cpu0->stack = stackptr;
>>  			cpu0->lowcore = (void *)0;
>