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authorChristian Borntraeger <borntraeger@de.ibm.com>2017-05-15 14:11:03 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-06-17 06:39:38 +0200
commitd80aa84235ff7b2b13cd204e23a5823770512690 (patch)
treefaea44557169893e230ef290803db64d62dd16b1
parentafb415f72daa0d9d8169a20f3ea3efbf05f630ca (diff)
s390/kvm: do not rely on the ILC on kvm host protection fauls
commit c0e7bb38c07cbd8269549ee0a0566021a3c729de upstream. For most cases a protection exception in the host (e.g. copy on write or dirty tracking) on the sie instruction will indicate an instruction length of 4. Turns out that there are some corner cases (e.g. runtime instrumentation) where this is not necessarily true and the ILC is unpredictable. Let's replace our 4 byte rewind_pad with 3 byte nops to prepare for all possible ILCs. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/s390/kernel/entry.S19
1 files changed, 13 insertions, 6 deletions
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 7460df3eec6b..4612ed7ec2e5 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -229,12 +229,17 @@ ENTRY(sie64a)
lctlg %c1,%c1,__LC_USER_ASCE # load primary asce
.Lsie_done:
# some program checks are suppressing. C code (e.g. do_protection_exception)
-# will rewind the PSW by the ILC, which is 4 bytes in case of SIE. Other
-# instructions between sie64a and .Lsie_done should not cause program
-# interrupts. So lets use a nop (47 00 00 00) as a landing pad.
+# will rewind the PSW by the ILC, which is often 4 bytes in case of SIE. There
+# are some corner cases (e.g. runtime instrumentation) where ILC is unpredictable.
+# Other instructions between sie64a and .Lsie_done should not cause program
+# interrupts. So lets use 3 nops as a landing pad for all possible rewinds.
# See also .Lcleanup_sie
-.Lrewind_pad:
- nop 0
+.Lrewind_pad6:
+ nopr 7
+.Lrewind_pad4:
+ nopr 7
+.Lrewind_pad2:
+ nopr 7
.globl sie_exit
sie_exit:
lg %r14,__SF_EMPTY+8(%r15) # load guest register save area
@@ -247,7 +252,9 @@ sie_exit:
stg %r14,__SF_EMPTY+16(%r15) # set exit reason code
j sie_exit
- EX_TABLE(.Lrewind_pad,.Lsie_fault)
+ EX_TABLE(.Lrewind_pad6,.Lsie_fault)
+ EX_TABLE(.Lrewind_pad4,.Lsie_fault)
+ EX_TABLE(.Lrewind_pad2,.Lsie_fault)
EX_TABLE(sie_exit,.Lsie_fault)
#endif