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| author | Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> | 2019-02-08 14:33:19 +0000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2019-02-22 00:10:15 +1100 |
| commit | fe1ef6bcdb4fca33434256a802a3ed6aacf0bd2f (patch) | |
| tree | d3c8b03223a92da3a63170b6a7cf321aa12c6523 /arch | |
| parent | 9f3ba362d84786af8e1ab36a32fb337882b8648c (diff) | |
| download | linux-fe1ef6bcdb4fca33434256a802a3ed6aacf0bd2f.tar.bz2 | |
powerpc: Fix 32-bit KVM-PR lockup and host crash with MacOS guest
Commit 8792468da5e1 "powerpc: Add the ability to save FPU without
giving it up" unexpectedly removed the MSR_FE0 and MSR_FE1 bits from
the bitmask used to update the MSR of the previous thread in
__giveup_fpu() causing a KVM-PR MacOS guest to lockup and panic the
host kernel.
Leaving FE0/1 enabled means unrelated processes might receive FPEs
when they're not expecting them and crash. In particular if this
happens to init the host will then panic.
eg (transcribed):
qemu-system-ppc[837]: unhandled signal 8 at 12cc9ce4 nip 12cc9ce4 lr 12cc9ca4 code 0
systemd[1]: unhandled signal 8 at 202f02e0 nip 202f02e0 lr 001003d4 code 0
Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
Reinstate these bits to the MSR bitmask to enable MacOS guests to run
under 32-bit KVM-PR once again without issue.
Fixes: 8792468da5e1 ("powerpc: Add the ability to save FPU without giving it up")
Cc: stable@vger.kernel.org # v4.6+
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/powerpc/kernel/process.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index ce393df243aa..71bad4b6f80d 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -176,7 +176,7 @@ static void __giveup_fpu(struct task_struct *tsk) save_fpu(tsk); msr = tsk->thread.regs->msr; - msr &= ~MSR_FP; + msr &= ~(MSR_FP|MSR_FE0|MSR_FE1); #ifdef CONFIG_VSX if (cpu_has_feature(CPU_FTR_VSX)) msr &= ~MSR_VSX; |