On Sat, 19 May 2018 15:56:38 +1000
Paul Mackerras <paulus@xxxxxxxxxx> wrote:
> This relaxes the restriction on using PR KVM on POWER9. The existing
> code does work inside a guest partition running in HPT mode, because
> hypercalls such as H_ENTER use the old HPTE format, not the new
> format used by POWER9, and so no change to PR KVM's HPT manipulation
> code is required. PR KVM will still refuse to run if the kernel is
> using radix translation or if it is running bare-metal.
>
> Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx>
> ---
Paul,
I have built a 4.16.0 kernel + this patch and booted the L1 guest
with "disable_radix=on". I could then successfully boot a L2 guest,
using the same kernel for simplicity. Both guests using identical
fedora28 images. So it seems to be working at first sight.
But, if I boot the L2 guest with the default fedora28 kernel, ie
4.16.9-300.fc28.ppc64le, the L2 guest hangs.
OF stdout device is: /vdevice/vty@71000000
Preparing to boot Linux version 4.16.9-300.fc28.ppc64le (mockbuild@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) (gcc version 8.1.1 20180502 (Red Hat 8.1.1-1) (GCC)) #1 SMP Thu May 17 04:31:32 UTC 2018
Detected machine type: 0000000000000101
command line: BOOT_IMAGE=/boot/vmlinuz-4.16.9-300.fc28.ppc64le root=UUID=22128c5c-30b1-4e0a-ac16-95853df31131 ro rhgb console=hvc0 early_printk LANG=en_US.UTF-8
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 : 0000000004e70000
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 0x0000000004e80000 -> 0x0000000004e80aaf
Device tree struct 0x0000000004e90000 -> 0x0000000004ea0000
Quiescing Open Firmware ...
Booting Linux via __start() @ 0x0000000002000000 ...
(qemu) p $pc
0xc000000000026aa0
(qemu) p $lr
0xc000000000119ff4
# addr2line -e /usr/lib/debug/lib/modules/4.16.9-300.fc28.ppc64le/vmlinux 0xc000000000026aa0
/usr/src/debug/kernel-4.16.fc28/linux-4.16.9-300.fc28.ppc64le/./arch/powerpc/include/asm/time.h:115
# addr2line -e /usr/lib/debug/lib/modules/4.16.9-300.fc28.ppc64le/vmlinux 0xc000000000119ff4
/usr/src/debug/kernel-4.16.fc28/linux-4.16.9-300.fc28.ppc64le/kernel/panic.c:300
ie, the final mdelay(PANIC_TIMER_STEP) in panic().
Not sure how to debug this further, any suggestion is welcome :)
Cheers,
--
Greg
> arch/powerpc/kvm/book3s_pr.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
> index 67061d3..3d0251e 100644
> --- a/arch/powerpc/kvm/book3s_pr.c
> +++ b/arch/powerpc/kvm/book3s_pr.c
> @@ -1735,9 +1735,16 @@ static void kvmppc_core_destroy_vm_pr(struct kvm *kvm)
> static int kvmppc_core_check_processor_compat_pr(void)
> {
> /*
> - * Disable KVM for Power9 untill the required bits merged.
> + * PR KVM can work on POWER9 inside a guest partition
> + * running in HPT mode. It can't work if we are using
> + * radix translation (because radix provides no way for
> + * a process to have unique translations in quadrant 3)
> + * or in a bare-metal HPT-mode host (because POWER9
> + * uses a modified HPTE format which the PR KVM code
> + * has not been adapted to use).
> */
> - if (cpu_has_feature(CPU_FTR_ARCH_300))
> + if (cpu_has_feature(CPU_FTR_ARCH_300) &&
> + (radix_enabled() || cpu_has_feature(CPU_FTR_HVMODE)))
> return -EIO;
> return 0;
> }
