On Thu, Dec 22, 2016 at 04:29:27AM +1000, Nicholas Piggin wrote: > 64-bit Book3S exception handlers must find the dynamic kernel base > to add to the target address when branching beyond __end_interrupts, > in order to support kernel running at non-0 physical address. > > Support this in KVM by branching with CTR, similarly to regular > interrupt handlers. The guest CTR saved in HSTATE_SCRATCH1 and > restored after the branch. > > Without this, the host kernel hangs and crashes randomly when it is > running at a non-0 address and a KVM guest is started. > > Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx> Unfortunately, this patch causes guests to crash in various ways when running under a CONFIG_RELOCATABLE kernel. See below... > diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S > index 11882aac8216..c18ce740452b 100644 > --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S > +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S > @@ -1060,15 +1060,16 @@ kvmppc_interrupt_hv: > * R12 = (guest CR << 32) | interrupt vector > * R13 = PACA > * guest R12 saved in shadow VCPU SCRATCH0 > + * guest CTR saved in shadow VCPU SCRATCH1 if RELOCATABLE > * guest R13 saved in SPRN_SCRATCH0 > */ > - std r9, HSTATE_SCRATCH1(r13) > + std r9, HSTATE_SCRATCH2(r13) > lbz r9, HSTATE_IN_GUEST(r13) > cmpwi r9, KVM_GUEST_MODE_HOST_HV > beq kvmppc_bad_host_intr > #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE > cmpwi r9, KVM_GUEST_MODE_GUEST > - ld r9, HSTATE_SCRATCH1(r13) > + ld r9, HSTATE_SCRATCH2(r13) > beq kvmppc_interrupt_pr > #endif > /* We're now back in the host but in guest MMU context */ > @@ -1088,7 +1089,7 @@ kvmppc_interrupt_hv: > std r6, VCPU_GPR(R6)(r9) > std r7, VCPU_GPR(R7)(r9) > std r8, VCPU_GPR(R8)(r9) > - ld r0, HSTATE_SCRATCH1(r13) > + ld r0, HSTATE_SCRATCH2(r13) > std r0, VCPU_GPR(R9)(r9) > std r10, VCPU_GPR(R10)(r9) > std r11, VCPU_GPR(R11)(r9) > @@ -1151,7 +1152,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) > 11: stw r3,VCPU_HEIR(r9) > > /* these are volatile across C function calls */ > +#ifdef CONFIG_RELOCATABLE > + ld r3, HSTATE_SCRATCH1(r13) The problem is here. Depending on what sort of interrupt it is, we can end up going back to the guest via fast_guest_return, which doesn't reload CTR. Adding mtctr r3 at this point makes things work. Paul. -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
