powerpc: Fix 32-bit KVM-PR lockup and host crash with MacOS guest
Commit 8792468d "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: 8792468d ("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>
parent
9f3ba362
Please register or sign in to comment