KVM: s390: add capability indicating COW support
Currently qemu/kvm on s390 uses a guest mapping that does not
allow the guest backing page table to be write-protected to
support older systems. On those older systems a host write
protection fault will be delivered to the guest.
Newer systems allow to write-protect the guest backing memory
and let the fault be delivered to the host, thus allowing COW.
Use a capability bit to tell qemu if that is possible.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/drivers/s390/char/sclp_cmd.c b/drivers/s390/char/sclp_cmd.c
index 231a1d8..032171e 100644
--- a/drivers/s390/char/sclp_cmd.c
+++ b/drivers/s390/char/sclp_cmd.c
@@ -17,6 +17,7 @@
#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/memory.h>
+#include <linux/module.h>
#include <linux/platform_device.h>
#include <asm/chpid.h>
#include <asm/sclp.h>
@@ -38,7 +39,8 @@
u64 facilities; /* 48-55 */
u8 _reserved2[84 - 56]; /* 56-83 */
u8 fac84; /* 84 */
- u8 _reserved3[91 - 85]; /* 85-90 */
+ u8 fac85; /* 85 */
+ u8 _reserved3[91 - 86]; /* 86-90 */
u8 flags; /* 91 */
u8 _reserved4[100 - 92]; /* 92-99 */
u32 rnsize2; /* 100-103 */
@@ -51,6 +53,7 @@
u64 sclp_facilities;
static u8 sclp_fac84;
+static u8 sclp_fac85;
static unsigned long long rzm;
static unsigned long long rnmax;
@@ -112,6 +115,7 @@
sccb = &early_read_info_sccb;
sclp_facilities = sccb->facilities;
sclp_fac84 = sccb->fac84;
+ sclp_fac85 = sccb->fac85;
rnmax = sccb->rnmax ? sccb->rnmax : sccb->rnmax2;
rzm = sccb->rnsize ? sccb->rnsize : sccb->rnsize2;
rzm <<= 20;
@@ -127,6 +131,12 @@
return rzm;
}
+u8 sclp_get_fac85(void)
+{
+ return sclp_fac85;
+}
+EXPORT_SYMBOL_GPL(sclp_get_fac85);
+
/*
* This function will be called after sclp_facilities_detect(), which gets
* called from early.c code. Therefore the sccb should have valid contents.