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
mkcompile_h
#!/bin/sh
# SPDX-License-Identifier: GPL-2.0
TARGET=$1
ARCH=$2
SMP=$3
PREEMPT=$4
PREEMPT_RT=$5
CC=$6
LD=$7
vecho() { [ "${quiet}" = "silent_" ] || echo "$@" ; }
# Do not expand names
set -f
# Fix the language to get consistent output
LC_ALL=C
export LC_ALL
if [ -z "$KBUILD_BUILD_VERSION" ]; then
VERSION=$(cat .version 2>/dev/null || echo 1)
else
VERSION=$KBUILD_BUILD_VERSION
fi
if [ -z "$KBUILD_BUILD_TIMESTAMP" ]; then
TIMESTAMP=`date`
else
TIMESTAMP=$KBUILD_BUILD_TIMESTAMP
fi
if test -z "$KBUILD_BUILD_USER"; then
LINUX_COMPILE_BY=$(whoami | sed 's/\\/\\\\/')
else
LINUX_COMPILE_BY=$KBUILD_BUILD_USER
fi
if test -z "$KBUILD_BUILD_HOST"; then
LINUX_COMPILE_HOST=`hostname`
else
LINUX_COMPILE_HOST=$KBUILD_BUILD_HOST
fi
UTS_VERSION="#$VERSION"
CONFIG_FLAGS=""
if [ -n "$SMP" ] ; then CONFIG_FLAGS="SMP"; fi
if [ -n "$PREEMPT" ] ; then CONFIG_FLAGS="$CONFIG_FLAGS PREEMPT"; fi
if [ -n "$PREEMPT_RT" ] ; then CONFIG_FLAGS="$CONFIG_FLAGS PREEMPT_RT"; fi
# Truncate to maximum length
UTS_LEN=64
UTS_VERSION="$(echo $UTS_VERSION $CONFIG_FLAGS $TIMESTAMP | cut -b -$UTS_LEN)"
# Generate a temporary compile.h
{ echo /\* This file is auto generated, version $VERSION \*/
if [ -n "$CONFIG_FLAGS" ] ; then echo "/* $CONFIG_FLAGS */"; fi
echo \#define UTS_MACHINE \"$ARCH\"
echo \#define UTS_VERSION \"$UTS_VERSION\"
printf '#define LINUX_COMPILE_BY "%s"\n' "$LINUX_COMPILE_BY"
echo \#define LINUX_COMPILE_HOST \"$LINUX_COMPILE_HOST\"
CC_VERSION=$($CC -v 2>&1 | grep ' version ' | sed 's/[[:space:]]*$//')
LD_VERSION=$($LD -v | head -n1 | sed 's/(compatible with [^)]*)//' \
| sed 's/[[:space:]]*$//')
printf '#define LINUX_COMPILER "%s"\n' "$CC_VERSION, $LD_VERSION"
} > .tmpcompile
# Only replace the real compile.h if the new one is different,
# in order to preserve the timestamp and avoid unnecessary
# recompilations.
# We don't consider the file changed if only the date/time changed.
# A kernel config change will increase the generation number, thus
# causing compile.h to be updated (including date/time) due to the
# changed comment in the
# first line.
if [ -r $TARGET ] && \
grep -v 'UTS_VERSION' $TARGET > .tmpver.1 && \
grep -v 'UTS_VERSION' .tmpcompile > .tmpver.2 && \
cmp -s .tmpver.1 .tmpver.2; then
rm -f .tmpcompile
else
vecho " UPD $TARGET"
mv -f .tmpcompile $TARGET
fi
rm -f .tmpver.1 .tmpver.2
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