Re: [Qemu-ppc] [PATCH for-2.13 03/10] target/ppc: Remove unnecessary initialization of LPCR_UPRT

[Cédric Le Goater]

On 04/17/2018 09:17 AM, David Gibson wrote:
> In cpu_ppc_set_papr() the UPRT and GTSE bits of the LPCR are initialized
> based on on ppc64_radix_guest().  Which seems reasonable, except that
> ppc64_radix_guest() is based on spapr->patb_entry which is only set up
> in spapr_machine_reset, called much later than cpu_ppc_set_papr().
> 
> So the initialization here is pointless.  The base cpu initialization
> already sets a value that's good enough until the guest uses an hcall to
> configure it's preferred MMU mode.
> 
> Signed-off-by: David Gibson <address@hidden>
> ---
>  target/ppc/translate_init.c | 16 ----------------
>  1 file changed, 16 deletions(-)
> 
> diff --git a/target/ppc/translate_init.c b/target/ppc/translate_init.c
> index bb79d23b50..14f346f441 100644
> --- a/target/ppc/translate_init.c
> +++ b/target/ppc/translate_init.c
> @@ -8897,22 +8897,6 @@ void cpu_ppc_set_papr(PowerPCCPU *cpu, 
> PPCVirtualHypervisor *vhyp)
>      lpcr->default_value &= ~LPCR_RMLS;
>      lpcr->default_value |= 1ull << LPCR_RMLS_SHIFT;
>  
> -    if (env->mmu_model == POWERPC_MMU_3_00) {
> -        /* By default we choose legacy mode and switch to new hash or radix
> -         * when a register process table hcall is made. So disable process
> -         * tables and guest translation shootdown by default
> -         *
> -         * Hot-plugged CPUs inherit from the guest radix setting under
> -         * KVM but not under TCG. Update the default LPCR to keep new
> -         * CPUs in sync when radix is enabled.
> -         */


This is breaking CPU hotplug under TCG. Should we reintroduce the same 
settings in spapr_cpu_reset() now ?

Thanks,

C. 


> -        if (ppc64_radix_guest(cpu)) {
> -            lpcr->default_value |= LPCR_UPRT | LPCR_GTSE;
> -        } else {
> -            lpcr->default_value &= ~(LPCR_UPRT | LPCR_GTSE);
> -        }
> -    }
> -
>      /* Only enable Power-saving mode Exit Cause exceptions on the boot
>       * CPU. The RTAS command start-cpu will enable them on secondaries.
>       */
>