On Fri, 25 May 2018 16:13:13 +0200 Laurent Vivier <lviv...@redhat.com> wrote:
> On 25/05/2018 14:54, Greg Kurz wrote: > > Since the kernel commit "dbfcf3cb9c68 powerpc/64: Call H_REGISTER_PROC_TBL > > when running as a HPT guest on POWER9", a nested guest running with PR KVM > > hangs at boot: > > > > Preparing to boot Linux version 4.16.0-kvm-pr-hang-gku+ > > (greg@qemu2222.boston16) (gcc version 8.1.1 20180502 (Red Hat 8.1.1-1) > > (GCC)) #19 SMP Fri May 25 08:41:55 CEST 2018 > > Detected machine type: 0000000000000101 > > command line: root=UUID=22128c5c-30b1-4e0a-ac16-95853df31131 ro rhgb > > console=hvc0 early_printk disable-radix=on > > Max number of cores passed to firmware: 1024 (NR_CPUS = 1024) > > Calling ibm,client-architecture-support... done > > memory layout at init: > > memory_limit : 0000000000000000 (16 MB aligned) > > alloc_bottom : 0000000001b80000 > > alloc_top : 0000000030000000 > > alloc_top_hi : 0000000100000000 > > rmo_top : 0000000030000000 > > ram_top : 0000000100000000 > > instantiating rtas at 0x000000002fff0000... done > > prom_hold_cpus: skipped > > copying OF device tree... > > Building dt strings... > > Building dt structure... > > Device tree strings 0x0000000003d90000 -> 0x0000000003d90abb > > Device tree struct 0x0000000003da0000 -> 0x0000000003db0000 > > Quiescing Open Firmware ... > > Booting Linux via __start() @ 0x0000000000400000 ... > > > > This happens because the H_REGISTER_PROC_TBL implementation in QEMU > > always call KVM_PPC_CONFIGURE_V3_MMU when KVM is present. This fails > > in the case of PR KVM, which doesn't implement it, and QEMU returns > > H_PARAMETER to the guest, which is a BUG() condition in linux. > > > > In the case of PR, the HPT is allocated in userspace by QEMU, so it > > doesn't make sense to call KVM_PPC_CONFIGURE_V3_MMU in the first > > place. So, skip it in this case and let the guest boot. > > > > Signed-off-by: Greg Kurz <gr...@kaod.org> > > --- > > > > Note that PR KVM requires this patch from Paul to work on POWER9: > > > > https://patchwork.ozlabs.org/patch/916766/ > > > > The original request was coming from people who want to run openQA in > > fedora28 under PowerVM on a POWER9 system. This requires PR KVM, which > > will be running in HPT-mode since pHyp doesn't do radix. > > > > Cc'ing stable because fedora28 ships QEMU 2.11.x. > > --- > > hw/ppc/spapr_hcall.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c > > index 022f6d810182..12cbb317e5e8 100644 > > --- a/hw/ppc/spapr_hcall.c > > +++ b/hw/ppc/spapr_hcall.c > > @@ -1420,7 +1420,7 @@ static target_ulong > > h_register_process_table(PowerPCCPU *cpu, > > ((flags & FLAG_GTSE) ? LPCR_GTSE : 0), > > LPCR_UPRT | LPCR_GTSE); > > > > - if (kvm_enabled()) { > > + if (kvm_enabled() && !spapr->htab) { > > return kvmppc_configure_v3_mmu(cpu, flags & FLAG_RADIX, > > flags & FLAG_GTSE, cproc); > > } > > > > I'm wondering if you should use kvmppc_has_cap_mmu_hash_v3() instead? > The meaning of KVM_CAP_PPC_HASH_MMU_V3 is basically: KVM supports POWER9 hash... even if that would *work* when using PR KVM, I'm not sure this helps to understand. The true reason for not calling kvmppc_configure_v3_mmu() is that we already know that we're using a QEMU-side HPT. > Thanks, > Laurent Cheers, -- Greg
