KVM: PPC: Book3S: Fix CONFIG_TRANSACTIONAL_MEM=n crash

When running CPU_FTR_P9_TM_HV_ASSIST, HFSCR[TM] is set for the guest
even if the host has CONFIG_TRANSACTIONAL_MEM=n, which causes it to be
unprepared to handle guest exits while transactional.

Normal guests don't have a problem because the HTM capability will not
be advertised, but a rogue or buggy one could crash the host.

Fixes: 4bb3c7a0208f ("KVM: PPC: Book3S HV: Work around transactional memory bugs in POWER9")
Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210716024310.164448-1-npiggin@gmail.com

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 1d1fcc290fca4aa53a49a10115911da45b5c19e5..085fb8ecbf6884f91a2a0473ce223cf8595bccfe 100644 (file)
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -2697,8 +2697,10 @@ static int kvmppc_core_vcpu_create_hv(struct kvm_vcpu *vcpu)
                HFSCR_DSCR | HFSCR_VECVSX | HFSCR_FP | HFSCR_PREFIX;
        if (cpu_has_feature(CPU_FTR_HVMODE)) {
                vcpu->arch.hfscr &= mfspr(SPRN_HFSCR);
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
                if (cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST))
                        vcpu->arch.hfscr |= HFSCR_TM;
+#endif
        }
        if (cpu_has_feature(CPU_FTR_TM_COMP))
                vcpu->arch.hfscr |= HFSCR_TM;