Re: [PATCH qemu] spapr/ddw: Implement 64bit query extension

[Daniel Henrique Barboza <danielhb413@gmail.com>]

On 6/23/22 04:31, Alexey Kardashevskiy wrote:
> PAPR 2.8 (2018) defines an extension to return 64bit value for
> the largest TCE block in "ibm,query-pe-dma-window". Recent Linux kernels
> support this already.
> 
> This adds the extension and supports the older format.
> 
> This advertises a bigger window for the new format as the biggest
> window with 2M pages below the start of the 64bit window as it is
> the maximum we will see in practice.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---

Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>

>   hw/ppc/spapr_pci.c      |  5 +++--
>   hw/ppc/spapr_rtas_ddw.c | 19 +++++++++++++++----
>   2 files changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index 5e95d7940fc8..67e9d468aa9c 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -2360,8 +2360,9 @@ int spapr_dt_phb(SpaprMachineState *spapr, SpaprPhbState *phb,
>           cpu_to_be32(RTAS_IBM_REMOVE_PE_DMA_WINDOW)
>       };
>       uint32_t ddw_extensions[] = {
> -        cpu_to_be32(1),
> -        cpu_to_be32(RTAS_IBM_RESET_PE_DMA_WINDOW)
> +        cpu_to_be32(2),
> +        cpu_to_be32(RTAS_IBM_RESET_PE_DMA_WINDOW),
> +        cpu_to_be32(1), /* 1: ibm,query-pe-dma-window 6 outputs, PAPR 2.8 */
>       };
>       SpaprTceTable *tcet;
>       SpaprDrc *drc;
> diff --git a/hw/ppc/spapr_rtas_ddw.c b/hw/ppc/spapr_rtas_ddw.c
> index bb7d91b6d1af..7ba11382bc3f 100644
> --- a/hw/ppc/spapr_rtas_ddw.c
> +++ b/hw/ppc/spapr_rtas_ddw.c
> @@ -100,7 +100,7 @@ static void rtas_ibm_query_pe_dma_window(PowerPCCPU *cpu,
>       uint64_t buid;
>       uint32_t avail, addr, pgmask = 0;
>   
> -    if ((nargs != 3) || (nret != 5)) {
> +    if ((nargs != 3) || ((nret != 5) && (nret != 6))) {
>           goto param_error_exit;
>       }
>   
> @@ -118,9 +118,20 @@ static void rtas_ibm_query_pe_dma_window(PowerPCCPU *cpu,
>   
>       rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>       rtas_st(rets, 1, avail);
> -    rtas_st(rets, 2, 0x80000000); /* The largest window we can possibly have */
> -    rtas_st(rets, 3, pgmask);
> -    rtas_st(rets, 4, 0); /* DMA migration mask, not supported */
> +    if (nret == 6) {
> +        /*
> +         * Set the Max TCE number as 1<<(58-21) = 0x20.0000.0000
> +         * 1<<59 is the huge window start and 21 is 2M page shift.
> +         */
> +        rtas_st(rets, 2, 0x00000020);
> +        rtas_st(rets, 3, 0x00000000);
> +        rtas_st(rets, 4, pgmask);
> +        rtas_st(rets, 5, 0); /* DMA migration mask, not supported */
> +    } else {
> +        rtas_st(rets, 2, 0x80000000);
> +        rtas_st(rets, 3, pgmask);
> +        rtas_st(rets, 4, 0); /* DMA migration mask, not supported */
> +    }
>   
>       trace_spapr_iommu_ddw_query(buid, addr, avail, 0x80000000, pgmask);
>       return;