Re: [Qemu-devel] KVM-PR is broken with current QEMU

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Tue, 2016-09-20 at 13:44 +0200, Thomas Huth wrote:
> 
> 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?
> I can make KVM PR working again with the following patch:
> 
> 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?

Oh I thought I had removed the degraded variants ... Definitely looks
like an accident. I *think* PR KVM supports 64K pages, no ? If not,
then we shouldn't enable the flag.. somebody needs to check the kernel.

Cheers,
Ben.