Re: [kvm-unit-tests PATCH v1 1/5] s390x: css: Store CSS Characteristics

[Pierre Morel <pmorel@linux.ibm.com>]

On 2/2/21 6:25 PM, Thomas Huth wrote:
> On 29/01/2021 15.34, Pierre Morel wrote:
>> CSS characteristics exposes the features of the Channel SubSystem.
>> Let's use Store Channel Subsystem Characteristics to retrieve
>> the features of the CSS.
>>
>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>> ---
>>   lib/s390x/css.h     | 57 +++++++++++++++++++++++++++++++++++++++++++++
>>   lib/s390x/css_lib.c | 50 ++++++++++++++++++++++++++++++++++++++-
>>   s390x/css.c         | 12 ++++++++++
>>   3 files changed, 118 insertions(+), 1 deletion(-)
>>
>> diff --git a/lib/s390x/css.h b/lib/s390x/css.h
>> index 3e57445..bc0530d 100644
>> --- a/lib/s390x/css.h
>> +++ b/lib/s390x/css.h
>> @@ -288,4 +288,61 @@ int css_residual_count(unsigned int schid);
>>   void enable_io_isc(uint8_t isc);
>>   int wait_and_check_io_completion(int schid);
>> +/*
>> + * CHSC definitions
>> + */
>> +struct chsc_header {
>> +    u16 len;
>> +    u16 code;
>> +};
>> +
>> +/* Store Channel Subsystem Characteristics */
>> +struct chsc_scsc {
>> +    struct chsc_header req;
>> +    u32 reserved1;
>> +    u32 reserved2;
>> +    u32 reserved3;
>> +    struct chsc_header res;
>> +    u32 format;
>> +    u64 general_char[255];
>> +    u64 chsc_char[254];
>> +};
>> +extern struct chsc_scsc *chsc_scsc;
>> +
>> +#define CSS_GENERAL_FEAT_BITLEN    (255 * 64)
>> +#define CSS_CHSC_FEAT_BITLEN    (254 * 64)
>> +
>> +int get_chsc_scsc(void);
>> +
>> +static inline int _chsc(void *p)
>> +{
>> +    int cc;
>> +
>> +    asm volatile(
>> +        "    .insn   rre,0xb25f0000,%2,0\n"
>> +        "    ipm     %0\n"
>> +        "    srl     %0,28\n"
>> +        : "=d" (cc), "=m" (p)
>> +        : "d" (p), "m" (p)
>> +        : "cc");
>> +
>> +    return cc;
>> +}
>> +
>> +#define CHSC_SCSC    0x0010
>> +#define CHSC_SCSC_LEN    0x0010
>> +
>> +static inline int chsc(void *p, uint16_t code, uint16_t len)
>> +{
>> +    struct chsc_header *h = p;
>> +
>> +    h->code = code;
>> +    h->len = len;
>> +    return _chsc(p);
>> +}
>> +
>> +#include <bitops.h>
>> +#define css_general_feature(bit) test_bit_inv(bit, 
>> chsc_scsc->general_char)
>> +#define css_chsc_feature(bit) test_bit_inv(bit, chsc_scsc->chsc_char)
>> +
>>   #endif
>> diff --git a/lib/s390x/css_lib.c b/lib/s390x/css_lib.c
>> index 3c24480..fe05021 100644
>> --- a/lib/s390x/css_lib.c
>> +++ b/lib/s390x/css_lib.c
>> @@ -15,11 +15,59 @@
>>   #include <asm/arch_def.h>
>>   #include <asm/time.h>
>>   #include <asm/arch_def.h>
>> -
>> +#include <alloc_page.h>
>>   #include <malloc_io.h>
>>   #include <css.h>
>>   static struct schib schib;
>> +struct chsc_scsc *chsc_scsc;
>> +
>> +int get_chsc_scsc(void)
>> +{
>> +    int i, n;
>> +    int ret = 0;
>> +    char buffer[510];
>> +    char *p;
>> +
>> +    report_prefix_push("Channel Subsystem Call");
>> +
>> +    if (chsc_scsc) {
>> +        report_info("chsc_scsc already initialized");
>> +        goto end;
>> +    }
>> +
>> +    chsc_scsc = alloc_pages(0);
>> +    report_info("scsc_scsc at: %016lx", (u64)chsc_scsc);
>> +    if (!chsc_scsc) {
>> +        ret = -1;
>> +        report(0, "could not allocate chsc_scsc page!");
>> +        goto end;
>> +    }
>> +
>> +    ret = chsc(chsc_scsc, CHSC_SCSC, CHSC_SCSC_LEN);
>> +    if (ret) {
>> +        report(0, "chsc: CC %d", ret);
>> +        goto end;
>> +    }
>> +
>> +    for (i = 0, p = buffer; i < CSS_GENERAL_FEAT_BITLEN; i++)
>> +        if (css_general_feature(i)) {
>> +            n = snprintf(p, sizeof(buffer) - ret, "%d,", i);
>> +            p += n;
>> +        }
>> +    report_info("General features: %s", buffer);
>> +
>> +    for (i = 0, p = buffer, ret = 0; i < CSS_CHSC_FEAT_BITLEN; i++)
>> +        if (css_chsc_feature(i)) {
>> +            n = snprintf(p, sizeof(buffer) - ret, "%d,", i);
>> +            p += n;
>> +        }
> 
> Please use curly braces for the for-loops here, too. Rationale: Kernel 
> coding style:
> 
> "Also, use braces when a loop contains more than a single simple statement"

OK, is better to read.

Thanks,
Pierre


> 
>   Thanks,
>    Thomas
> 

-- 
Pierre Morel
IBM Lab Boeblingen