Re: [PATCH qemu v2] spapr/ddw: Reset DMA when the last non-default window is removed

[Daniel Henrique Barboza]

On 6/22/22 02:29, Alexey Kardashevskiy wrote:
> PAPR+/LoPAPR says:
> ===
> The platform must restore the default DMA window for the PE on a call
> to the ibm,remove-pe-dma-window RTAS call when all of the following
> are true:
>   a. The call removes the last DMA window remaining for the PE.
>   b. The DMA window being removed is not the default window
>
> ===
>
> This resets DMA as PAPR mandates.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---

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

> Changes:
> v2:
> * reverted changes to spapr_tce_table_enable()
> ---
>   include/hw/ppc/spapr.h  |  1 +
>   hw/ppc/spapr_iommu.c    |  3 ++-
>   hw/ppc/spapr_pci.c      |  1 +
>   hw/ppc/spapr_rtas_ddw.c | 15 +++++++++++++++
>   4 files changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 072dda2c7265..4ba2b27b8c4f 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -902,6 +902,7 @@ struct SpaprTceTable {
>       bool bypass;
>       bool need_vfio;
>       bool skipping_replay;
> +    bool def_win;
>       int fd;
>       MemoryRegion root;
>       IOMMUMemoryRegion iommu;
> diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
> index 81e5a1aea3a6..63e34d457a0e 100644
> --- a/hw/ppc/spapr_iommu.c
> +++ b/hw/ppc/spapr_iommu.c
> @@ -279,7 +279,7 @@ static const VMStateDescription vmstate_spapr_tce_table_ex 
> = {
>   
>   static const VMStateDescription vmstate_spapr_tce_table = {
>       .name = "spapr_iommu",
> -    .version_id = 2,
> +    .version_id = 3,
>       .minimum_version_id = 2,
>       .pre_save = spapr_tce_table_pre_save,
>       .post_load = spapr_tce_table_post_load,
> @@ -292,6 +292,7 @@ static const VMStateDescription vmstate_spapr_tce_table = {
>           VMSTATE_BOOL(bypass, SpaprTceTable),
>           VMSTATE_VARRAY_UINT32_ALLOC(mig_table, SpaprTceTable, mig_nb_table, 0,
>                                       vmstate_info_uint64, uint64_t),
> +        VMSTATE_BOOL_V(def_win, SpaprTceTable, 3),
>   
>           VMSTATE_END_OF_LIST()
>       },
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index b2f5fbef0c83..5e95d7940fc8 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -2067,6 +2067,7 @@ void spapr_phb_dma_reset(SpaprPhbState *sphb)
>       tcet = spapr_tce_find_by_liobn(sphb->dma_liobn[0]);
>       spapr_tce_table_enable(tcet, SPAPR_TCE_PAGE_SHIFT, sphb->dma_win_addr,
>                              sphb->dma_win_size >> SPAPR_TCE_PAGE_SHIFT);
> +    tcet->def_win = true;
>   }
>   
>   static void spapr_phb_reset(DeviceState *qdev)
> diff --git a/hw/ppc/spapr_rtas_ddw.c b/hw/ppc/spapr_rtas_ddw.c
> index 13d339c807c1..bb7d91b6d1af 100644
> --- a/hw/ppc/spapr_rtas_ddw.c
> +++ b/hw/ppc/spapr_rtas_ddw.c
> @@ -215,6 +215,7 @@ static void rtas_ibm_remove_pe_dma_window(PowerPCCPU *cpu,
>       SpaprPhbState *sphb;
>       SpaprTceTable *tcet;
>       uint32_t liobn;
> +    bool def_win_removed;
>   
>       if ((nargs != 1) || (nret != 1)) {
>           goto param_error_exit;
> @@ -231,9 +232,23 @@ static void rtas_ibm_remove_pe_dma_window(PowerPCCPU *cpu,
>           goto param_error_exit;
>       }
>   
> +    def_win_removed = tcet->def_win;
>       spapr_tce_table_disable(tcet);
>       trace_spapr_iommu_ddw_remove(liobn);
>   
> +    /*
> +     * PAPR+/LoPAPR says:
> +     * The platform must restore the default DMA window for the PE on a call
> +     * to the ibm,remove-pe-dma-window RTAS call when all of the following
> +     * are true:
> +     * a. The call removes the last DMA window remaining for the PE.
> +     * b. The DMA window being removed is not the default window
> +     */
> +    if (spapr_phb_get_active_win_num(sphb) == 0 && !def_win_removed) {
> +        spapr_phb_dma_reset(sphb);
> +        trace_spapr_iommu_ddw_reset(sphb->buid, 0);
> +    }
> +
>       rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>       return;
>