spapr/ddw: Reset DMA when the last non-default window is removed

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>
Message-Id: <20220622052955.1069903-1-aik@ozlabs.ru>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>

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()
     },

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)

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;
 

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;