On 18.01.19 12:42, 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/arch_def.h | 1 +
> lib/s390x/asm/interrupt.h | 2 ++
> lib/s390x/interrupt.c | 12 +++++++++--
> lib/s390x/sclp-console.c | 2 ++
> lib/s390x/sclp.c | 54 +++++++++++++++++++++++++++++++++++++++++++++--
> lib/s390x/sclp.h | 3 +++
> 6 files changed, 70 insertions(+), 4 deletions(-)
>
> diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
> index d2cd727..4bbb428 100644
> --- a/lib/s390x/asm/arch_def.h
> +++ b/lib/s390x/asm/arch_def.h
> @@ -15,6 +15,7 @@ struct psw {
> uint64_t addr;
> };
>
> +#define PSW_MASK_EXT 0x0100000000000000UL
> #define PSW_MASK_DAT 0x0400000000000000UL
> #define PSW_MASK_PSTATE 0x0001000000000000UL
>
> 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 7f556e5..9876db3 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>
>
> @@ -24,6 +26,8 @@ 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)
> {
> @@ -32,17 +36,61 @@ static void mem_init(phys_addr_t mem_end)
> phys_alloc_init(freemem_start, mem_end - freemem_start);
> }
>
> +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);
With multiple CPUs, this is problematic. Just when the interrupt comes
in, SCLP is marked as !busy and the SCCB block can immediately be reused
by other callers waiting in sclp_mark_busy().
Wasn't the idea to also protect the whole global SCCB?
We should maybe stop using a gloval page and instead get one per caller
via the page allocator. Or let the caller of sclp_mark_busy() set SCLP
as !busy once he's done handling the block.
> +}
> +
> +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.
> + */
> +retry_wait:
> + sclp_wait_busy();
> + spin_lock(&sclp_lock);
> + if (sclp_busy) {
> + spin_unlock(&sclp_lock);
> + goto retry_wait;
> + }
> + sclp_busy = true;
> + 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;
> @@ -57,12 +105,14 @@ 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);
>
--
Thanks,
David / dhildenb
