Re: [Qemu-devel] [PATCH] ppc/kvm: Mark 64kB page size support as disabled if not available

[Michael Roth <mdroth@linux.vnet.ibm.com>]

Quoting Thomas Huth (2016-09-21 04:42:15)
> QEMU currently refuses to start with KVM-PR and only prints out
> 
>         qemu: fatal: Unknown MMU model 851972
> 
> when being started there. This is because commit 4322e8ced5aaac719
> ("ppc: Fix 64K pages support in full emulation") introduced a new
> POWERPC_MMU_64K bit to indicate support for this page size, but
> it never gets cleared on KVM-PR if the host kernel does not support
> this. Thus we've got to turn off this bit in the mmu_model for KVM-PR.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>

Cc'ing qemu-stable

> ---
>  target-ppc/kvm.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
> index dcb68b9..6bdc804 100644
> --- a/target-ppc/kvm.c
> +++ b/target-ppc/kvm.c
> @@ -427,6 +427,7 @@ static void kvm_fixup_page_sizes(PowerPCCPU *cpu)
>      CPUPPCState *env = &cpu->env;
>      long rampagesize;
>      int iq, ik, jq, jk;
> +    bool has_64k_pages = false;
> 
>      /* We only handle page sizes for 64-bit server guests for now */
>      if (!(env->mmu_model & POWERPC_MMU_64)) {
> @@ -470,6 +471,9 @@ static void kvm_fixup_page_sizes(PowerPCCPU *cpu)
>                                       ksps->enc[jk].page_shift)) {
>                  continue;
>              }
> +            if (ksps->enc[jk].page_shift == 16) {
> +                has_64k_pages = true;
> +            }
>              qsps->enc[jq].page_shift = ksps->enc[jk].page_shift;
>              qsps->enc[jq].pte_enc = ksps->enc[jk].pte_enc;
>              if (++jq >= PPC_PAGE_SIZES_MAX_SZ) {
> @@ -484,6 +488,9 @@ static void kvm_fixup_page_sizes(PowerPCCPU *cpu)
>      if (!(smmu_info.flags & KVM_PPC_1T_SEGMENTS)) {
>          env->mmu_model &= ~POWERPC_MMU_1TSEG;
>      }
> +    if (!has_64k_pages) {
> +        env->mmu_model &= ~POWERPC_MMU_64K;
> +    }
>  }
>  #else /* defined (TARGET_PPC64) */
> 
> -- 
> 1.8.3.1
> 
>