Patchwork [kvm-unit-tests,v2,5/6] s390x: Use interrupts in SCLP

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Submitter Janosch Frank
Date Dec. 5, 2018, 3:39 p.m.
Message ID <20181205153918.29480-6-frankja@linux.ibm.com>
Download mbox | patch
Permalink /patch/673229/
State New
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Comments

Janosch Frank - Dec. 5, 2018, 3:39 p.m.
We need to properly implement interrupt handling for SCLP, because on
z/VM and LPAR SCLP calls are not synchronous!

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
---
 lib/s390x/asm/arch_def.h  |  1 +
 lib/s390x/asm/interrupt.h |  2 ++
 lib/s390x/interrupt.c     | 12 ++++++++++--
 lib/s390x/io.c            |  2 +-
 lib/s390x/sclp-console.c  | 29 +++++++++--------------------
 lib/s390x/sclp.c          | 42 ++++++++++++++++++++++++++++++++++++++++++
 lib/s390x/sclp.h          |  4 +++-
 7 files changed, 68 insertions(+), 24 deletions(-)
David Hildenbrand - Dec. 5, 2018, 7:27 p.m.
On 05.12.18 16:39, Janosch Frank wrote:
> We need to properly implement interrupt handling for SCLP, because on
> z/VM and LPAR SCLP calls are not synchronous!
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
>  lib/s390x/asm/arch_def.h  |  1 +
>  lib/s390x/asm/interrupt.h |  2 ++
>  lib/s390x/interrupt.c     | 12 ++++++++++--
>  lib/s390x/io.c            |  2 +-
>  lib/s390x/sclp-console.c  | 29 +++++++++--------------------
>  lib/s390x/sclp.c          | 42 ++++++++++++++++++++++++++++++++++++++++++
>  lib/s390x/sclp.h          |  4 +++-
>  7 files changed, 68 insertions(+), 24 deletions(-)
> 
> diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
> index d2d6e02..27c6b85 100644
> --- a/lib/s390x/asm/arch_def.h
> +++ b/lib/s390x/asm/arch_def.h
> @@ -33,6 +33,7 @@ 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..de15d9e 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..7118577 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/io.c b/lib/s390x/io.c
> index 05a0765..7294165 100644
> --- a/lib/s390x/io.c
> +++ b/lib/s390x/io.c
> @@ -45,8 +45,8 @@ void setup(void)
>  {
>  	setup_args_progname(ipl_args);
>  	setup_facilities();
> -	sclp_console_setup();
>  	sclp_memory_setup();
> +	sclp_console_setup();
>  }
>  
>  void exit(int code)
> diff --git a/lib/s390x/sclp-console.c b/lib/s390x/sclp-console.c
> index deacbde..13ab03d 100644
> --- a/lib/s390x/sclp-console.c
> +++ b/lib/s390x/sclp-console.c
> @@ -13,30 +13,13 @@
>  #include <asm/page.h>
>  #include "sclp.h"
>  
> -char _sccb[PAGE_SIZE] __attribute__((__aligned__(4096)));
> -
> -/* Perform service call. Return 0 on success, non-zero otherwise. */
> -int sclp_service_call(unsigned int command, void *sccb)
> -{
> -        int cc;
> -
> -        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");
> -        if (cc == 3)
> -                return -1;
> -        if (cc == 2)
> -                return -1;
> -        return 0;
> -}
> -
>  static void sclp_set_write_mask(void)
>  {
>  	WriteEventMask *sccb = (void *)_sccb;
>  
> +	while (sclp_busy)
> +		/* Wait for SCLP request to complete */;

should we use barrier(); here to make this clearer?

> +	sclp_busy = true;
>  	sccb->h.length = sizeof(WriteEventMask);
>  	sccb->mask_length = sizeof(unsigned int);
>  	sccb->receive_mask = SCLP_EVENT_MASK_MSG_ASCII;
> @@ -57,6 +40,9 @@ void sclp_print(const char *str)
>  	int len = strlen(str);
>  	WriteEventData *sccb = (void *)_sccb;
>  
> +	while (sclp_busy)
> +		/* Wait for SCLP request to complete */;

dito

(I guess do not we need barriers between setting sclp_busy and testing
it, because we're using volatile and we don't have multi-threading
messing with the value)

> +	sclp_busy = true;
>  	sccb->h.length = sizeof(WriteEventData) + len;
>  	sccb->h.function_code = SCLP_FC_NORMAL_WRITE;
>  	sccb->ebh.length = sizeof(EventBufferHeader) + len;
> @@ -65,4 +51,7 @@ void sclp_print(const char *str)
>  	memcpy(sccb->data, str, len);
>  
>  	sclp_service_call(SCLP_CMD_WRITE_EVENT_DATA, sccb);
> +	while (sclp_busy)
> +		/* Wait for SCLP request to complete */;

dito

> +
>  }
> diff --git a/lib/s390x/sclp.c b/lib/s390x/sclp.c
> index 1d4a010..cd0e5e5 100644
> --- a/lib/s390x/sclp.c
> +++ b/lib/s390x/sclp.c
> @@ -23,6 +23,9 @@ static uint64_t storage_increment_size;
>  static uint64_t max_ram_size;
>  static uint64_t ram_size;
>  
> +char _sccb[PAGE_SIZE] __attribute__((__aligned__(4096)));
> +volatile bool sclp_busy = false;

false should be the default value already.

> +
>  static void mem_init(phys_addr_t mem_end)
>  {
>  	phys_addr_t freemem_start = (phys_addr_t)&stacktop;
> @@ -30,6 +33,42 @@ 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)
> +{

Error out if !sclp_busy but we get an interrupt?

> +	ctl_clear_bit(0, 9);
> +	sclp_busy = false;
> +}
> +
> +/* Perform service call. Return 0 on success, non-zero otherwise. */
> +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");
> +        if (cc == 3)
> +                return -1;
> +        if (cc == 2)
> +                return -1;
> +        return 0;
> +}

Guess moving that (including _sccb) could also be a separate patch ;)

> +
>  void sclp_memory_setup(void)
>  {
>  	ReadInfo *ri = (void *)_sccb;
> @@ -37,7 +76,10 @@ void sclp_memory_setup(void)
>  	int cc;
>  
>  	ri->h.length = SCCB_SIZE;
> +	sclp_busy = true;
>  	sclp_service_call(SCLP_CMDW_READ_SCP_INFO_FORCED, ri);
> +	while (sclp_busy)
> +		/* Wait for SCLP request to complete */;

Should we factor that out into something like

sclp_start_request()
{
	sclp_busy = true;
}

sclp_wait_response()
{
	while (sclp_busy)
		barrier();
}

>  
>  	/* calculate the storage increment size */
>  	rnsize = ri->rnsize;
> diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
> index e008932..a91aad1 100644
> --- a/lib/s390x/sclp.h
> +++ b/lib/s390x/sclp.h
> @@ -207,9 +207,11 @@ typedef struct ReadEventData {
>      uint32_t mask;
>  } __attribute__((packed)) ReadEventData;
>  
> +extern char _sccb[];
> +volatile bool sclp_busy;
> +void sclp_handle_ext(void);
>  void sclp_console_setup(void);
>  void sclp_print(const char *str);
> -extern char _sccb[];
>  int sclp_service_call(unsigned int command, void *sccb);
>  void sclp_memory_setup(void);
>  
>
Janosch Frank - Dec. 6, 2018, 9:09 a.m.
On 05.12.18 20:27, David Hildenbrand wrote:
> On 05.12.18 16:39, Janosch Frank wrote:
>> We need to properly implement interrupt handling for SCLP, because on
>> z/VM and LPAR SCLP calls are not synchronous!
>>
>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>> ---
[]
>> -
>>  static void sclp_set_write_mask(void)
>>  {
>>  	WriteEventMask *sccb = (void *)_sccb;
>>  
>> +	while (sclp_busy)
>> +		/* Wait for SCLP request to complete */;
> 
> should we use barrier(); here to make this clearer?

I could factor that out in sclp_wait_busy(), to make it one place to
change. I thought about using spinlocks, but whatever we do, we have to
be careful to not print when holding the lock.

Maybe we need a sclp spinlock/busy bust error path for exit with > 0,
like we do in the kernel on a panic.

> 
>> +	sclp_busy = true;
>>  	sccb->h.length = sizeof(WriteEventMask);
>>  	sccb->mask_length = sizeof(unsigned int);
>>  	sccb->receive_mask = SCLP_EVENT_MASK_MSG_ASCII;
>> @@ -57,6 +40,9 @@ void sclp_print(const char *str)
>>  	int len = strlen(str);
>>  	WriteEventData *sccb = (void *)_sccb;
>>  
>> +	while (sclp_busy)
>> +		/* Wait for SCLP request to complete */;
> 
> dito
> 
> (I guess do not we need barriers between setting sclp_busy and testing
> it, because we're using volatile and we don't have multi-threading
> messing with the value)
> 
>> +	sclp_busy = true;
>>  	sccb->h.length = sizeof(WriteEventData) + len;
>>  	sccb->h.function_code = SCLP_FC_NORMAL_WRITE;
>>  	sccb->ebh.length = sizeof(EventBufferHeader) + len;
>> @@ -65,4 +51,7 @@ void sclp_print(const char *str)
>>  	memcpy(sccb->data, str, len);
>>  
>>  	sclp_service_call(SCLP_CMD_WRITE_EVENT_DATA, sccb);
>> +	while (sclp_busy)
>> +		/* Wait for SCLP request to complete */;
> 
> dito
> 
>> +
>>  }
>> diff --git a/lib/s390x/sclp.c b/lib/s390x/sclp.c
>> index 1d4a010..cd0e5e5 100644
>> --- a/lib/s390x/sclp.c
>> +++ b/lib/s390x/sclp.c
>> @@ -23,6 +23,9 @@ static uint64_t storage_increment_size;
>>  static uint64_t max_ram_size;
>>  static uint64_t ram_size;
>>  
>> +char _sccb[PAGE_SIZE] __attribute__((__aligned__(4096)));
>> +volatile bool sclp_busy = false;
> 
> false should be the default value already.

Yes, that's a leftover from the bss clearing problem, where it sometimes
was > 0...

> 
>> +
>>  static void mem_init(phys_addr_t mem_end)
>>  {
>>  	phys_addr_t freemem_start = (phys_addr_t)&stacktop;
>> @@ -30,6 +33,42 @@ 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)
>> +{
> 
> Error out if !sclp_busy but we get an interrupt?

Yes, but then I need to reset sclp_busy in the progress and we need to
hope that we get sclp output.

> 
>> +	ctl_clear_bit(0, 9);
>> +	sclp_busy = false;
>> +}
>> +
>> +/* Perform service call. Return 0 on success, non-zero otherwise. */
>> +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");
>> +        if (cc == 3)
>> +                return -1;
>> +        if (cc == 2)
>> +                return -1;
>> +        return 0;
>> +}
> 
> Guess moving that (including _sccb) could also be a separate patch ;)

Will do

> 
>> +
>>  void sclp_memory_setup(void)
>>  {
>>  	ReadInfo *ri = (void *)_sccb;
>> @@ -37,7 +76,10 @@ void sclp_memory_setup(void)
>>  	int cc;
>>  
>>  	ri->h.length = SCCB_SIZE;
>> +	sclp_busy = true;
>>  	sclp_service_call(SCLP_CMDW_READ_SCP_INFO_FORCED, ri);
>> +	while (sclp_busy)
>> +		/* Wait for SCLP request to complete */;
> 
> Should we factor that out into something like

As written above, I'm all for the second one, but I dislike the start
one liner.

> 
> sclp_start_request()
> {
> 	sclp_busy = true;
> }
> 
> sclp_wait_response()
> {
> 	while (sclp_busy)
> 		barrier();
> }
> 
>>  
>>  	/* calculate the storage increment size */
>>  	rnsize = ri->rnsize;
>> diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
>> index e008932..a91aad1 100644
>> --- a/lib/s390x/sclp.h
>> +++ b/lib/s390x/sclp.h
>> @@ -207,9 +207,11 @@ typedef struct ReadEventData {
>>      uint32_t mask;
>>  } __attribute__((packed)) ReadEventData;
>>  
>> +extern char _sccb[];
>> +volatile bool sclp_busy;
>> +void sclp_handle_ext(void);
>>  void sclp_console_setup(void);
>>  void sclp_print(const char *str);
>> -extern char _sccb[];
>>  int sclp_service_call(unsigned int command, void *sccb);
>>  void sclp_memory_setup(void);
>>  
>>
> 
>
David Hildenbrand - Dec. 6, 2018, 9:16 a.m.
> 
>>
>>> +
>>>  void sclp_memory_setup(void)
>>>  {
>>>  	ReadInfo *ri = (void *)_sccb;
>>> @@ -37,7 +76,10 @@ void sclp_memory_setup(void)
>>>  	int cc;
>>>  
>>>  	ri->h.length = SCCB_SIZE;
>>> +	sclp_busy = true;
>>>  	sclp_service_call(SCLP_CMDW_READ_SCP_INFO_FORCED, ri);
>>> +	while (sclp_busy)
>>> +		/* Wait for SCLP request to complete */;
>>
>> Should we factor that out into something like
> 
> As written above, I'm all for the second one, but I dislike the start
> one liner.
> 

Sure, fine with me!

Patch

diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
index d2d6e02..27c6b85 100644
--- a/lib/s390x/asm/arch_def.h
+++ b/lib/s390x/asm/arch_def.h
@@ -33,6 +33,7 @@  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..de15d9e 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..7118577 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/io.c b/lib/s390x/io.c
index 05a0765..7294165 100644
--- a/lib/s390x/io.c
+++ b/lib/s390x/io.c
@@ -45,8 +45,8 @@  void setup(void)
 {
 	setup_args_progname(ipl_args);
 	setup_facilities();
-	sclp_console_setup();
 	sclp_memory_setup();
+	sclp_console_setup();
 }
 
 void exit(int code)
diff --git a/lib/s390x/sclp-console.c b/lib/s390x/sclp-console.c
index deacbde..13ab03d 100644
--- a/lib/s390x/sclp-console.c
+++ b/lib/s390x/sclp-console.c
@@ -13,30 +13,13 @@ 
 #include <asm/page.h>
 #include "sclp.h"
 
-char _sccb[PAGE_SIZE] __attribute__((__aligned__(4096)));
-
-/* Perform service call. Return 0 on success, non-zero otherwise. */
-int sclp_service_call(unsigned int command, void *sccb)
-{
-        int cc;
-
-        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");
-        if (cc == 3)
-                return -1;
-        if (cc == 2)
-                return -1;
-        return 0;
-}
-
 static void sclp_set_write_mask(void)
 {
 	WriteEventMask *sccb = (void *)_sccb;
 
+	while (sclp_busy)
+		/* Wait for SCLP request to complete */;
+	sclp_busy = true;
 	sccb->h.length = sizeof(WriteEventMask);
 	sccb->mask_length = sizeof(unsigned int);
 	sccb->receive_mask = SCLP_EVENT_MASK_MSG_ASCII;
@@ -57,6 +40,9 @@  void sclp_print(const char *str)
 	int len = strlen(str);
 	WriteEventData *sccb = (void *)_sccb;
 
+	while (sclp_busy)
+		/* Wait for SCLP request to complete */;
+	sclp_busy = true;
 	sccb->h.length = sizeof(WriteEventData) + len;
 	sccb->h.function_code = SCLP_FC_NORMAL_WRITE;
 	sccb->ebh.length = sizeof(EventBufferHeader) + len;
@@ -65,4 +51,7 @@  void sclp_print(const char *str)
 	memcpy(sccb->data, str, len);
 
 	sclp_service_call(SCLP_CMD_WRITE_EVENT_DATA, sccb);
+	while (sclp_busy)
+		/* Wait for SCLP request to complete */;
+
 }
diff --git a/lib/s390x/sclp.c b/lib/s390x/sclp.c
index 1d4a010..cd0e5e5 100644
--- a/lib/s390x/sclp.c
+++ b/lib/s390x/sclp.c
@@ -23,6 +23,9 @@  static uint64_t storage_increment_size;
 static uint64_t max_ram_size;
 static uint64_t ram_size;
 
+char _sccb[PAGE_SIZE] __attribute__((__aligned__(4096)));
+volatile bool sclp_busy = false;
+
 static void mem_init(phys_addr_t mem_end)
 {
 	phys_addr_t freemem_start = (phys_addr_t)&stacktop;
@@ -30,6 +33,42 @@  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);
+	sclp_busy = false;
+}
+
+/* Perform service call. Return 0 on success, non-zero otherwise. */
+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");
+        if (cc == 3)
+                return -1;
+        if (cc == 2)
+                return -1;
+        return 0;
+}
+
 void sclp_memory_setup(void)
 {
 	ReadInfo *ri = (void *)_sccb;
@@ -37,7 +76,10 @@  void sclp_memory_setup(void)
 	int cc;
 
 	ri->h.length = SCCB_SIZE;
+	sclp_busy = true;
 	sclp_service_call(SCLP_CMDW_READ_SCP_INFO_FORCED, ri);
+	while (sclp_busy)
+		/* Wait for SCLP request to complete */;
 
 	/* calculate the storage increment size */
 	rnsize = ri->rnsize;
diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
index e008932..a91aad1 100644
--- a/lib/s390x/sclp.h
+++ b/lib/s390x/sclp.h
@@ -207,9 +207,11 @@  typedef struct ReadEventData {
     uint32_t mask;
 } __attribute__((packed)) ReadEventData;
 
+extern char _sccb[];
+volatile bool sclp_busy;
+void sclp_handle_ext(void);
 void sclp_console_setup(void);
 void sclp_print(const char *str);
-extern char _sccb[];
 int sclp_service_call(unsigned int command, void *sccb);
 void sclp_memory_setup(void);