Revision 595d153dd1022392083ac93a1550382cbee127e0 authored by Michael Ellerman on 26 May 2020, 06:18:08 UTC, committed by Michael Ellerman on 26 May 2020, 07:32:37 UTC
Commit 702f09805222 ("powerpc/64s/exception: Remove lite interrupt return") changed the interrupt return path to not restore non-volatile registers by default, and explicitly restore them in paths where it is required. But it missed that the facility unavailable exception can sometimes modify user registers, ie. when it does emulation of move from DSCR. This is seen as a failure of the dscr_sysfs_thread_test: test: dscr_sysfs_thread_test [cpu 0] User DSCR should be 1 but is 0 failure: dscr_sysfs_thread_test So restore non-volatile GPRs after facility unavailable exceptions. Currently the hypervisor facility unavailable exception is also wired up to call facility_unavailable_exception(). In practice we should never take a hypervisor facility unavailable exception for the DSCR. On older bare metal systems we set HFSCR_DSCR unconditionally in __init_HFSCR, or on newer systems it should be enabled via the "data-stream-control-register" device tree CPU feature. Even if it's not, since commit f3c99f97a3cd ("KVM: PPC: Book3S HV: Don't access HFSCR, LPIDR or LPCR when running nested"), the KVM code has unconditionally set HFSCR_DSCR when running guests. So we should only get a hypervisor facility unavailable for the DSCR if skiboot has disabled the "data-stream-control-register" feature, and we are somehow in guest context but not via KVM. Given all that, it should be unnecessary to add a restore of non-volatile GPRs after the hypervisor facility exception, because we never expect to hit that path. But equally we may as well add the restore, because we never expect to hit that path, and if we ever did, at least we would correctly restore the registers to their post emulation state. In future we can split the non-HV and HV facility unavailable handling so that there is no emulation in the HV handler, and then remove the restore for the HV case. Fixes: 702f09805222 ("powerpc/64s/exception: Remove lite interrupt return") Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20200526061808.2472279-1-mpe@ellerman.id.au
1 parent 8659a0e
show_delta
#!/usr/bin/python
# SPDX-License-Identifier: GPL-2.0-only
#
# show_deltas: Read list of printk messages instrumented with
# time data, and format with time deltas.
#
# Also, you can show the times relative to a fixed point.
#
# Copyright 2003 Sony Corporation
#
import sys
import string
def usage():
print ("""usage: show_delta [<options>] <filename>
This program parses the output from a set of printk message lines which
have time data prefixed because the CONFIG_PRINTK_TIME option is set, or
the kernel command line option "time" is specified. When run with no
options, the time information is converted to show the time delta between
each printk line and the next. When run with the '-b' option, all times
are relative to a single (base) point in time.
Options:
-h Show this usage help.
-b <base> Specify a base for time references.
<base> can be a number or a string.
If it is a string, the first message line
which matches (at the beginning of the
line) is used as the time reference.
ex: $ dmesg >timefile
$ show_delta -b NET4 timefile
will show times relative to the line in the kernel output
starting with "NET4".
""")
sys.exit(1)
# returns a tuple containing the seconds and text for each message line
# seconds is returned as a float
# raise an exception if no timing data was found
def get_time(line):
if line[0]!="[":
raise ValueError
# split on closing bracket
(time_str, rest) = string.split(line[1:],']',1)
time = string.atof(time_str)
#print "time=", time
return (time, rest)
# average line looks like:
# [ 0.084282] VFS: Mounted root (romfs filesystem) readonly
# time data is expressed in seconds.useconds,
# convert_line adds a delta for each line
last_time = 0.0
def convert_line(line, base_time):
global last_time
try:
(time, rest) = get_time(line)
except:
# if any problem parsing time, don't convert anything
return line
if base_time:
# show time from base
delta = time - base_time
else:
# just show time from last line
delta = time - last_time
last_time = time
return ("[%5.6f < %5.6f >]" % (time, delta)) + rest
def main():
base_str = ""
filein = ""
for arg in sys.argv[1:]:
if arg=="-b":
base_str = sys.argv[sys.argv.index("-b")+1]
elif arg=="-h":
usage()
else:
filein = arg
if not filein:
usage()
try:
lines = open(filein,"r").readlines()
except:
print ("Problem opening file: %s" % filein)
sys.exit(1)
if base_str:
print ('base= "%s"' % base_str)
# assume a numeric base. If that fails, try searching
# for a matching line.
try:
base_time = float(base_str)
except:
# search for line matching <base> string
found = 0
for line in lines:
try:
(time, rest) = get_time(line)
except:
continue
if string.find(rest, base_str)==1:
base_time = time
found = 1
# stop at first match
break
if not found:
print ('Couldn\'t find line matching base pattern "%s"' % base_str)
sys.exit(1)
else:
base_time = 0.0
for line in lines:
print (convert_line(line, base_time),)
main()
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