On Tue, 31 Jan 2017 19:01:52 +1100 Paul Mackerras <pau...@ozlabs.org> wrote:
> 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 <npig...@gmail.com> > > 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. Thanks for tracking it down. Not enough testing on my end, I'm sorry. Thanks, Nick
