Re: [kvm-unit-tests PATCH v3 1/6] s390x: Use interrupts in SCLP and add locking

David Hildenbrand
2019-09-20T08:12:57Z

On 20.09.19 10:03, 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@linux.ibm.com>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> ---
> 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);
>

Acked-by: David Hildenbrand <david@redhat.com>

--

Thanks,

David / dhildenb