Re: [Qemu-devel] [PATCH 2/2] ppc: Allow 64kiB pages for POWER8 in TCG

[Alexey Kardashevskiy]

On 12/21/2015 01:41 PM, David Gibson wrote:
> Now that the spapr code has been extended to support 64kiB pages, we can
> allow guests to use 64kiB pages on an emulated POWER8 by adding it to the
> "segment_page_sizes" structure which is advertised via the device tree.
>
> For now we just add support for 64kiB pages in 64kiB page segments.  Real
> POWER8 also supports 64kiB pages in 4kiB page segments, but that will
> require more work to implement.
>
> Real POWER7s (and maybe some other CPU models) also support 64kiB pages,
> however, I don't want to add support there without double checking if they
> use the same HPTE and SLB encodings (in principle these are implementation
> dependent).
>
> Signed-off-by: David Gibson <address@hidden>
> ---
>   target-ppc/translate_init.c | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
>
> diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
> index e88dc7f..ae5a269 100644
> --- a/target-ppc/translate_init.c
> +++ b/target-ppc/translate_init.c
> @@ -8200,6 +8200,22 @@ POWERPC_FAMILY(POWER8)(ObjectClass *oc, void *data)
>   {
>       DeviceClass *dc = DEVICE_CLASS(oc);
>       PowerPCCPUClass *pcc = POWERPC_CPU_CLASS(oc);
> +    static const struct ppc_segment_page_sizes POWER8_sps = {
> +        .sps = {
> +            { .page_shift = 12, /* 4K */
> +              .slb_enc = 0,
> +              .enc = { { .page_shift = 12, .pte_enc = 0 } }
> +            },
> +            { .page_shift = 16, /* 64K */
> +              .slb_enc = 0x110,
> +              .enc = { { .page_shift = 16, .pte_enc = 0x1 } }
> +            },
> +            { .page_shift = 24, /* 16M */
> +              .slb_enc = 0x100,
> +              .enc = { { .page_shift = 24, .pte_enc = 0 } }
> +            },
> +        }
> +    };


In order to educate myself - where did 0x110/0x100 come from? Is not 0x110 
SLB_VSID_64K (which does not use SLB_VSID_L by accident?)? And is 0x100 
SLB_VSID_L?

I just wanted to double check if POWER7 uses the same encoding and it is 
not that simple to trace what came from where...



>       dc->fw_name = "PowerPC,POWER8";
>       dc->desc = "POWER8";
> @@ -8258,6 +8274,7 @@ POWERPC_FAMILY(POWER8)(ObjectClass *oc, void *data)
>       pcc->l1_dcache_size = 0x8000;
>       pcc->l1_icache_size = 0x8000;
>       pcc->interrupts_big_endian = ppc_cpu_interrupts_big_endian_lpcr;
> +    pcc->sps = &POWER8_sps;
>   }
>   #endif /* defined (TARGET_PPC64) */


--
Alexey