On 9/10/19 1:24 PM, David Hildenbrand wrote:
> On 10.09.19 12:14, David Hildenbrand wrote:
>> On 05.09.19 12:39, Janosch Frank wrote:
>>> We need to properly implement interrupt handling for SCLP, because on
>>> z/VM and LPAR SCLP calls are not synchronous!
>>>
>>> Also with smp CPUs have to compete for sclp. Let's add some locking,
>>> so they execute sclp calls in an orderly fashion and don't compete for
>>> the data buffer.
>>>
>>> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
>>> ---
>>> lib/s390x/asm/interrupt.h | 2 ++
>>> lib/s390x/interrupt.c | 12 +++++++--
>>> lib/s390x/sclp-console.c | 2 ++
>>> lib/s390x/sclp.c | 55 +++++++++++++++++++++++++++++++++++++--
>>> lib/s390x/sclp.h | 3 +++
>>> 5 files changed, 70 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/lib/s390x/asm/interrupt.h b/lib/s390x/asm/interrupt.h
>>> index 013709f..f485e96 100644
>>> --- a/lib/s390x/asm/interrupt.h
>>> +++ b/lib/s390x/asm/interrupt.h
>>> @@ -11,6 +11,8 @@
>>> #define _ASMS390X_IRQ_H_
>>> #include <asm/arch_def.h>
>>>
>>> +#define EXT_IRQ_SERVICE_SIG 0x2401
>>> +
>>> void handle_pgm_int(void);
>>> void handle_ext_int(void);
>>> void handle_mcck_int(void);
>>> diff --git a/lib/s390x/interrupt.c b/lib/s390x/interrupt.c
>>> index cf0a794..7832711 100644
>>> --- a/lib/s390x/interrupt.c
>>> +++ b/lib/s390x/interrupt.c
>>> @@ -12,6 +12,7 @@
>>> #include <libcflat.h>
>>> #include <asm/interrupt.h>
>>> #include <asm/barrier.h>
>>> +#include <sclp.h>
>>>
>>> static bool pgm_int_expected;
>>> static struct lowcore *lc;
>>> @@ -107,8 +108,15 @@ void handle_pgm_int(void)
>>>
>>> void handle_ext_int(void)
>>> {
>>> - report_abort("Unexpected external call interrupt: at %#lx",
>>> - lc->ext_old_psw.addr);
>>> + if (lc->ext_int_code != EXT_IRQ_SERVICE_SIG) {
>>> + report_abort("Unexpected external call interrupt: at %#lx",
>>> + lc->ext_old_psw.addr);
>>> + } else {
>>> + lc->ext_old_psw.mask &= ~PSW_MASK_EXT;
>>> + lc->sw_int_cr0 &= ~(1UL << 9);
>>> + sclp_handle_ext();
>>> + lc->ext_int_code = 0;
>>> + }
>>> }
>>>
>>> void handle_mcck_int(void)
>>> diff --git a/lib/s390x/sclp-console.c b/lib/s390x/sclp-console.c
>>> index bc01f41..a5ef45f 100644
>>> --- a/lib/s390x/sclp-console.c
>>> +++ b/lib/s390x/sclp-console.c
>>> @@ -17,6 +17,7 @@ static void sclp_set_write_mask(void)
>>> {
>>> WriteEventMask *sccb = (void *)_sccb;
>>>
>>> + sclp_mark_busy();
>>> sccb->h.length = sizeof(WriteEventMask);
>>> sccb->mask_length = sizeof(unsigned int);
>>> sccb->receive_mask = SCLP_EVENT_MASK_MSG_ASCII;
>>> @@ -37,6 +38,7 @@ void sclp_print(const char *str)
>>> int len = strlen(str);
>>> WriteEventData *sccb = (void *)_sccb;
>>>
>>> + sclp_mark_busy();
>>> sccb->h.length = sizeof(WriteEventData) + len;
>>> sccb->h.function_code = SCLP_FC_NORMAL_WRITE;
>>> sccb->ebh.length = sizeof(EventBufferHeader) + len;
>>> diff --git a/lib/s390x/sclp.c b/lib/s390x/sclp.c
>>> index b60f7a4..56fca0c 100644
>>> --- a/lib/s390x/sclp.c
>>> +++ b/lib/s390x/sclp.c
>>> @@ -14,6 +14,8 @@
>>> #include <asm/page.h>
>>> #include <asm/arch_def.h>
>>> #include <asm/interrupt.h>
>>> +#include <asm/barrier.h>
>>> +#include <asm/spinlock.h>
>>> #include "sclp.h"
>>> #include <alloc_phys.h>
>>> #include <alloc_page.h>
>>> @@ -25,6 +27,8 @@ static uint64_t max_ram_size;
>>> static uint64_t ram_size;
>>>
>>> char _sccb[PAGE_SIZE] __attribute__((__aligned__(4096)));
>>> +static volatile bool sclp_busy;
>>> +static struct spinlock sclp_lock;
>>>
>>> static void mem_init(phys_addr_t mem_end)
>>> {
>>> @@ -41,17 +45,62 @@ static void mem_init(phys_addr_t mem_end)
>>> page_alloc_ops_enable();
>>> }
>>>
>>> +static void sclp_setup_int(void)
>>> +{
>>> + uint64_t mask;
>>> +
>>> + ctl_set_bit(0, 9);
>>> +
>>> + mask = extract_psw_mask();
>>> + mask |= PSW_MASK_EXT;
>>> + load_psw_mask(mask);
>>> +}
>>> +
>>> +void sclp_handle_ext(void)
>>> +{
>>> + ctl_clear_bit(0, 9);
>>> + spin_lock(&sclp_lock);
>>> + sclp_busy = false;
>>> + spin_unlock(&sclp_lock);
>>> +}
>>> +
>>> +void sclp_wait_busy(void)
>>> +{
>>> + while (sclp_busy)
>>> + mb();
>>> +}
>>> +
>>> +void sclp_mark_busy(void)
>>> +{
>>> + /*
>>> + * With multiple CPUs we might need to wait for another CPU's
>>> + * request before grabbing the busy indication.
>>> + */
>>> + while (true) {
>>> + sclp_wait_busy();
>>> + spin_lock(&sclp_lock);
>>> + if (!sclp_busy) {
>>> + sclp_busy = true;
>>> + spin_unlock(&sclp_lock);
>>> + return;
>>> + }
>>> + spin_unlock(&sclp_lock);
>>> + }
>>> +}
>>> +
>>> static void sclp_read_scp_info(ReadInfo *ri, int length)
>>> {
>>> unsigned int commands[] = { SCLP_CMDW_READ_SCP_INFO_FORCED,
>>> SCLP_CMDW_READ_SCP_INFO };
>>> - int i;
>>> + int i, cc;
>>>
>>> for (i = 0; i < ARRAY_SIZE(commands); i++) {
>>> + sclp_mark_busy();
>>> memset(&ri->h, 0, sizeof(ri->h));
>>> ri->h.length = length;
>>>
>>> - if (sclp_service_call(commands[i], ri))
>>> + cc = sclp_service_call(commands[i], ri);
>>> + if (cc)
>>> break;
>>> if (ri->h.response_code == SCLP_RC_NORMAL_READ_COMPLETION)
>>> return;
>>> @@ -66,12 +115,14 @@ int sclp_service_call(unsigned int command, void *sccb)
>>> {
>>> int cc;
>>>
>>> + sclp_setup_int();
>>> asm volatile(
>>> " .insn rre,0xb2200000,%1,%2\n" /* servc %1,%2 */
>>> " ipm %0\n"
>>> " srl %0,28"
>>> : "=&d" (cc) : "d" (command), "a" (__pa(sccb))
>>> : "cc", "memory");
>>> + sclp_wait_busy();
>>> if (cc == 3)
>>> return -1;
>>> if (cc == 2)
>>> diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
>>> index 583c4e5..63cf609 100644
>>> --- a/lib/s390x/sclp.h
>>> +++ b/lib/s390x/sclp.h
>>> @@ -213,6 +213,9 @@ typedef struct ReadEventData {
>>> } __attribute__((packed)) ReadEventData;
>>>
>>> extern char _sccb[];
>>> +void sclp_handle_ext(void);
>>> +void sclp_wait_busy(void);
>>> +void sclp_mark_busy(void);
>>> void sclp_console_setup(void);
>>> void sclp_print(const char *str);
>>> int sclp_service_call(unsigned int command, void *sccb);
>>>
>>
>> I was wondering whether it would make sense to enable sclp interrupts as
>> default for all CPUs (once in a reasonable state after brought up), and
>> simply let any CPU process the request. Initially, we could only let the
>> boot CPU handle them.
>>
>> You already decoupled sclp_mark_busy() and sclp_setup_int() already. The
>> part would have to be moved to the CPU init stage and sclp_handle_ext()
>> would simply not clear the interrupt-enable flag.
>>
>> Opinions?
>>
>
> OTOH, the s390x-ccw bios enables interrupts on the single cpu after
> sending the request, and disables them again in the interrupt handler. I
> guess we should never get more than one interrupt per SCLP request?
>
Didn't old qemu versions do exactly that an we currently catch that in
the kernel?
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