s390: run user space and KVM guests with modified branch prediction

Define TIF_ISOLATE_BP and TIF_ISOLATE_BP_GUEST and add the necessary
plumbing in entry.S to be able to run user space and KVM guests with
limited branch prediction.

To switch a user space process to limited branch prediction the
s390_isolate_bp() function has to be call, and to run a vCPU of a KVM
guest associated with the current task with limited branch prediction
call s390_isolate_bp_guest().

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

2 files changed, 7 insertions, 0 deletions

diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 5f37f9ceef5e..7f2953c15c37 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -378,6 +378,9 @@ extern void memcpy_absolute(void *, void *, size_t);
         memcpy_absolute(&(dest), &__tmp, sizeof(__tmp));        \
 } while (0)
 
+extern int s390_isolate_bp(void);
+extern int s390_isolate_bp_guest(void);
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* __ASM_S390_PROCESSOR_H */
diff --git a/arch/s390/include/asm/thread_info.h b/arch/s390/include/asm/thread_info.h
index 25d6ec3aaddd..83ba57533ce6 100644
--- a/arch/s390/include/asm/thread_info.h
+++ b/arch/s390/include/asm/thread_info.h
@@ -58,6 +58,8 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
 #define TIF_GUARDED_STORAGE     4       /* load guarded storage control block */
 #define TIF_PATCH_PENDING       5       /* pending live patching update */
 #define TIF_PGSTE               6       /* New mm's will use 4K page tables */
+#define TIF_ISOLATE_BP          8       /* Run process with isolated BP */
+#define TIF_ISOLATE_BP_GUEST    9       /* Run KVM guests with isolated BP */
 
 #define TIF_31BIT               16      /* 32bit process */
 #define TIF_MEMDIE              17      /* is terminating due to OOM killer */
@@ -78,6 +80,8 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
 #define _TIF_UPROBE             _BITUL(TIF_UPROBE)
 #define _TIF_GUARDED_STORAGE    _BITUL(TIF_GUARDED_STORAGE)
 #define _TIF_PATCH_PENDING      _BITUL(TIF_PATCH_PENDING)
+#define _TIF_ISOLATE_BP         _BITUL(TIF_ISOLATE_BP)
+#define _TIF_ISOLATE_BP_GUEST   _BITUL(TIF_ISOLATE_BP_GUEST)
 
 #define _TIF_31BIT              _BITUL(TIF_31BIT)
 #define _TIF_SINGLE_STEP        _BITUL(TIF_SINGLE_STEP)