s390/cpcmd,vmcp: avoid GFP_DMA allocations

According to the CP Programming Services manual Diagnose Code 8
"Virtual Console Function" can be used in all addressing modes. Also
the input and output buffers do not have a limitation which specifies
they need to be below the 2GB line.

This is true at least since z/VM 5.4.

Therefore remove the sam31/64 instructions and allow for simple
GFP_KERNEL allocations. This makes it easier to allocate a 1MB page
if the user requested such a large return buffer.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

3 files changed, 8 insertions, 14 deletions

diff --git a/arch/s390/include/asm/cpcmd.h b/arch/s390/include/asm/cpcmd.h
index 3dfadb5d648f..ca2b0624ad46 100644
--- a/arch/s390/include/asm/cpcmd.h
+++ b/arch/s390/include/asm/cpcmd.h
@@ -10,9 +10,8 @@
 
 /*
  * the lowlevel function for cpcmd
- * the caller of __cpcmd has to ensure that the response buffer is below 2 GB
  */
-extern int __cpcmd(const char *cmd, char *response, int rlen, int *response_code);
+int __cpcmd(const char *cmd, char *response, int rlen, int *response_code);
 
 /*
  * cpcmd is the in-kernel interface for issuing CP commands
@@ -25,8 +24,8 @@ extern int __cpcmd(const char *cmd, char *response, int rlen, int *response_code
  * response_code: return pointer for VM's error code
  * return value: the size of the response. The caller can check if the buffer
  *              was large enough by comparing the return value and rlen
- * NOTE: If the response buffer is not below 2 GB, cpcmd can sleep
+ * NOTE: If the response buffer is not in real storage, cpcmd can sleep
  */
-extern int cpcmd(const char *cmd, char *response, int rlen, int *response_code);
+int cpcmd(const char *cmd, char *response, int rlen, int *response_code);
 
 #endif /* _ASM_S390_CPCMD_H */
diff --git a/arch/s390/kernel/cpcmd.c b/arch/s390/kernel/cpcmd.c
index 9f0e4a2785f7..63bc6603e0ed 100644
--- a/arch/s390/kernel/cpcmd.c
+++ b/arch/s390/kernel/cpcmd.c
@@ -14,6 +14,7 @@
 #include <linux/spinlock.h>
 #include <linux/stddef.h>
 #include <linux/string.h>
+#include <linux/mm.h>
 #include <asm/diag.h>
 #include <asm/ebcdic.h>
 #include <asm/cpcmd.h>
@@ -28,9 +29,7 @@ static int diag8_noresponse(int cmdlen)
         register unsigned long reg3 asm ("3") = cmdlen;
 
         asm volatile(
-                "       sam31\n"
                 "       diag    %1,%0,0x8\n"
-                "       sam64\n"
                 : "+d" (reg3) : "d" (reg2) : "cc");
         return reg3;
 }
@@ -43,9 +42,7 @@ static int diag8_response(int cmdlen, char *response, int *rlen)
         register unsigned long reg5 asm ("5") = *rlen;
 
         asm volatile(
-                "       sam31\n"
                 "       diag    %2,%0,0x8\n"
-                "       sam64\n"
                 "       brc     8,1f\n"
                 "       agr     %1,%4\n"
                 "1:\n"
@@ -57,7 +54,6 @@ static int diag8_response(int cmdlen, char *response, int *rlen)
 
 /*
  * __cpcmd has some restrictions over cpcmd
- *  - the response buffer must reside below 2GB (if any)
  *  - __cpcmd is unlocked and therefore not SMP-safe
  */
 int  __cpcmd(const char *cmd, char *response, int rlen, int *response_code)
@@ -88,13 +84,12 @@ EXPORT_SYMBOL(__cpcmd);
 
 int cpcmd(const char *cmd, char *response, int rlen, int *response_code)
 {
+        unsigned long flags;
         char *lowbuf;
         int len;
-        unsigned long flags;
 
-        if ((virt_to_phys(response) != (unsigned long) response) ||
-                        (((unsigned long)response + rlen) >> 31)) {
-                lowbuf = kmalloc(rlen, GFP_KERNEL | GFP_DMA);
+        if (is_vmalloc_or_module_addr(response)) {
+                lowbuf = kmalloc(rlen, GFP_KERNEL);
                 if (!lowbuf) {
                         pr_warn("The cpcmd kernel function failed to allocate a response buffer\n");
                         return -ENOMEM;
diff --git a/drivers/s390/char/vmcp.c b/drivers/s390/char/vmcp.c
index 66d5e9f83e0d..b5e3a49745f9 100644
--- a/drivers/s390/char/vmcp.c
+++ b/drivers/s390/char/vmcp.c
@@ -98,7 +98,7 @@ vmcp_write(struct file *file, const char __user *buff, size_t count,
         }
         if (!session->response)
                 session->response = (char *)__get_free_pages(GFP_KERNEL
-                                                | __GFP_RETRY_MAYFAIL | GFP_DMA,
+                                                | __GFP_RETRY_MAYFAIL,
                                                 get_order(session->bufsize));
         if (!session->response) {
                 mutex_unlock(&session->mutex);