On 09/20/2016 01:44 PM, Thomas Huth wrote:
> Hi,
>
> when I try to run my guest in KVM-PR mode, current QEMU refuses to start:
>
> $ sudo qemu-system-ppc64 -M pseries,accel=kvm,kvm-type=PR \
> -nographic -vga none -cpu POWER8
> qemu: fatal: Unknown MMU model 851972
>
> ... followed by a useless register dump. I've bisected the issue, and it
> seems like the problem has been introduced by this commit here:
>
> commit 4322e8ced5aaac7191958f09622d199fe61e2d87
> ppc: Fix 64K pages support in full emulation
>
> Seems like KVM PR is using the "degraded" ISA variants (without the 1TB
> segments), but the new POWERPC_MMU_64K flag has not been added to those.
> Has this been done on purpose, or was this just by accident?
The "degraded" architecture support has some history behind it :
commit 126a79300971 added it
commit aa4bb5875231 removed it.
commit ba3ecda05e93 readded it.
commit 4322e8ced5aa forgot about it again
> I can make KVM PR working again with the following patch:
I think this is correct. Let's wait for Ben to chime in :)
Thanks,
C.
> diff --git a/target-ppc/cpu-qom.h b/target-ppc/cpu-qom.h
> index 2864105..36694cb 100644
> --- a/target-ppc/cpu-qom.h
> +++ b/target-ppc/cpu-qom.h
> @@ -81,6 +81,7 @@ enum powerpc_mmu_t {
> | POWERPC_MMU_AMR | 0x00000003,
> /* Architecture 2.06 "degraded" (no 1T segments) */
> POWERPC_MMU_2_06a = POWERPC_MMU_64 | POWERPC_MMU_AMR
> + | POWERPC_MMU_64K
> | 0x00000003,
> /* Architecture 2.07 variant */
> POWERPC_MMU_2_07 = POWERPC_MMU_64 | POWERPC_MMU_1TSEG
> @@ -88,6 +89,7 @@ enum powerpc_mmu_t {
> | POWERPC_MMU_AMR | 0x00000004,
> /* Architecture 2.07 "degraded" (no 1T segments) */
> POWERPC_MMU_2_07a = POWERPC_MMU_64 | POWERPC_MMU_AMR
> + | POWERPC_MMU_64K
> | 0x00000004,
> };
>
> However, not sure whether this is the right fix ... Cédric, Ben, any ideas?
