[S390] kvm: fix address mode switching

598841ca9919d008b520114d8a4378c4ce4e40a1 ([S390] use gmap address
spaces for kvm guest images) changed kvm to use a separate address
space for kvm guests. This address space was switched in __vcpu_run
In some cases (preemption, page fault) there is the possibility that
this address space switch is lost.
The typical symptom was a huge amount of validity intercepts or
random guest addressing exceptions.
Fix this by doing the switch in sie_loop and sie_exit and saving the
address space in the gmap structure itself. Also use the preempt
notifier.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

2 files changed, 9 insertions, 0 deletions

diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
index 532fd4322156..2b45591e1582 100644
--- a/arch/s390/kernel/asm-offsets.c
+++ b/arch/s390/kernel/asm-offsets.c
@@ -10,6 +10,7 @@
 #include <linux/sched.h>
 #include <asm/vdso.h>
 #include <asm/sigp.h>
+#include <asm/pgtable.h>
 
 /*
  * Make sure that the compiler is new enough. We want a compiler that
@@ -126,6 +127,7 @@ int main(void)
         DEFINE(__LC_KERNEL_STACK, offsetof(struct _lowcore, kernel_stack));
         DEFINE(__LC_ASYNC_STACK, offsetof(struct _lowcore, async_stack));
         DEFINE(__LC_PANIC_STACK, offsetof(struct _lowcore, panic_stack));
+        DEFINE(__LC_USER_ASCE, offsetof(struct _lowcore, user_asce));
         DEFINE(__LC_INT_CLOCK, offsetof(struct _lowcore, int_clock));
         DEFINE(__LC_MCCK_CLOCK, offsetof(struct _lowcore, mcck_clock));
         DEFINE(__LC_MACHINE_FLAGS, offsetof(struct _lowcore, machine_flags));
@@ -151,6 +153,7 @@ int main(void)
         DEFINE(__LC_VDSO_PER_CPU, offsetof(struct _lowcore, vdso_per_cpu_data));
         DEFINE(__LC_GMAP, offsetof(struct _lowcore, gmap));
         DEFINE(__LC_CMF_HPP, offsetof(struct _lowcore, cmf_hpp));
+        DEFINE(__GMAP_ASCE, offsetof(struct gmap, asce));
 #endif /* CONFIG_32BIT */
         return 0;
 }
diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index 5f729d627cef..713da0760538 100644
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -1076,6 +1076,11 @@ sie_loop:
         lg      %r14,__LC_THREAD_INFO           # pointer thread_info struct
         tm      __TI_flags+7(%r14),_TIF_EXIT_SIE
         jnz     sie_exit
+        lg      %r14,__LC_GMAP                  # get gmap pointer
+        ltgr    %r14,%r14
+        jz      sie_gmap
+        lctlg   %c1,%c1,__GMAP_ASCE(%r14)       # load primary asce
+sie_gmap:
         lg      %r14,__SF_EMPTY(%r15)           # get control block pointer
         SPP     __SF_EMPTY(%r15)                # set guest id
         sie     0(%r14)
@@ -1083,6 +1088,7 @@ sie_done:
         SPP     __LC_CMF_HPP                    # set host id
         lg      %r14,__LC_THREAD_INFO           # pointer thread_info struct
 sie_exit:
+        lctlg   %c1,%c1,__LC_USER_ASCE          # load primary asce
         ni      __TI_flags+6(%r14),255-(_TIF_SIE>>8)
         lg      %r14,__SF_EMPTY+8(%r15)         # load guest register save area
         stmg    %r0,%r13,0(%r14)                # save guest gprs 0-13