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


From: Alexey Kardashevskiy
Subject: Re: [PATCH qemu] spapr/ddw: Reset DMA when the last non-default window is removed
Date: Wed, 22 Jun 2022 12:26:57 +1000
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.0



On 6/21/22 23:54, Daniel Henrique Barboza wrote:


On 6/20/22 05:01, 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>
---

Looks good. One comment below:


  include/hw/ppc/spapr.h  |  3 ++-
  hw/ppc/spapr_iommu.c    |  8 +++++---
  hw/ppc/spapr_pci.c      |  2 +-
  hw/ppc/spapr_rtas_ddw.c | 17 ++++++++++++++++-
  hw/ppc/spapr_vio.c      |  3 ++-
  5 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 072dda2c7265..0adbe1566d40 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;
@@ -928,7 +929,7 @@ void spapr_check_mmu_mode(bool guest_radix);
  SpaprTceTable *spapr_tce_new_table(DeviceState *owner, uint32_t liobn);
  void spapr_tce_table_enable(SpaprTceTable *tcet,
                              uint32_t page_shift, uint64_t bus_offset,
-                            uint32_t nb_table);
+                            uint32_t nb_table, bool def_win);

Do we need to add 'def_win' to spapr_tce_table_enable()? I see that you're using
the 'def_win' var to assign

+    tcet->def_win = def_win;

but the only case where def_win will be other than 'false' is:

- the function is called by spapr_tce_post_load(), but in that case it's being
callied like this:

     spapr_tce_table_enable(tcet, old_page_shift, old_bus_offset,
                            tcet->mig_nb_table, tcet->def_win);

which results in the function doing tcet->def_win = tcet->def_win, which is
uneeded.


- the function is called by spapr_phb_dma_reset(). In this case I believe
we can just do "tcet->def_win = true" before calling spapr_tce_table_enable():


      /* Register default 32bit DMA window */
      tcet = spapr_tce_find_by_liobn(sphb->dma_liobn[0]);
+     tcet->def_win = true;
      spapr_tce_table_enable(tcet, SPAPR_TCE_PAGE_SHIFT, sphb->dma_win_addr,
                             sphb->dma_win_size >> SPAPR_TCE_PAGE_SHIFT);
  }

All other calls to spapr_tce_table_enable() are passing 'false' to def_win and
can be left alone.

Assuming that there's no way a created DMA window becomes the default window, or
the default DMA window is demoted to non-default, I think we can leave
spapr_tce_table_enable() untouched and just set tcet->def_win to true inside
spapr_phb_dma_reset().


I can definitely do this. Thanks for the review, I'll repost.



Thanks,


Daniel



  void spapr_tce_table_disable(SpaprTceTable *tcet);
  void spapr_tce_set_need_vfio(SpaprTceTable *tcet, bool need_vfio);
diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
index 81e5a1aea3a6..f8c1627d0782 100644
--- a/hw/ppc/spapr_iommu.c
+++ b/hw/ppc/spapr_iommu.c
@@ -242,7 +242,7 @@ static int spapr_tce_table_post_load(void *opaque, int version_id)
      if (tcet->mig_nb_table) {
          if (!tcet->nb_table) {
              spapr_tce_table_enable(tcet, old_page_shift, old_bus_offset,
-                                   tcet->mig_nb_table);
+                                   tcet->mig_nb_table, tcet->def_win);
          }
          memcpy(tcet->table, tcet->mig_table,
@@ -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()
      },
@@ -380,7 +381,7 @@ SpaprTceTable *spapr_tce_new_table(DeviceState *owner, uint32_t liobn)
  void spapr_tce_table_enable(SpaprTceTable *tcet,
                              uint32_t page_shift, uint64_t bus_offset,
-                            uint32_t nb_table)
+                            uint32_t nb_table, bool def_win)
  {
      if (tcet->nb_table) {
          warn_report("trying to enable already enabled TCE table");
@@ -390,6 +391,7 @@ void spapr_tce_table_enable(SpaprTceTable *tcet,
      tcet->bus_offset = bus_offset;
      tcet->page_shift = page_shift;
      tcet->nb_table = nb_table;
+    tcet->def_win = def_win;
      tcet->table = spapr_tce_alloc_table(tcet->liobn,
                                          tcet->page_shift,
                                          tcet->bus_offset,
diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index b2f5fbef0c83..e1dbccfc7547 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -2066,7 +2066,7 @@ void spapr_phb_dma_reset(SpaprPhbState *sphb)
      /* Register default 32bit DMA window */
      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);
+                           sphb->dma_win_size >> SPAPR_TCE_PAGE_SHIFT, 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..4fe41b0c4539 100644
--- a/hw/ppc/spapr_rtas_ddw.c
+++ b/hw/ppc/spapr_rtas_ddw.c
@@ -182,7 +182,7 @@ static void rtas_ibm_create_pe_dma_window(PowerPCCPU *cpu,
       */
      tcet->skipping_replay = true;
      spapr_tce_table_enable(tcet, page_shift, win_addr,
-                           1ULL << (window_shift - page_shift));
+                           1ULL << (window_shift - page_shift), false);
      tcet->skipping_replay = false;
      if (!tcet->nb_table) {
          goto hw_error_exit;
@@ -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;
diff --git a/hw/ppc/spapr_vio.c b/hw/ppc/spapr_vio.c
index 9d4fec2c04d8..14506df19d62 100644
--- a/hw/ppc/spapr_vio.c
+++ b/hw/ppc/spapr_vio.c
@@ -533,7 +533,8 @@ static void spapr_vio_busdev_realize(DeviceState *qdev, Error **errp)
          dev->tcet = spapr_tce_new_table(qdev, liobn);
          spapr_tce_table_enable(dev->tcet, SPAPR_TCE_PAGE_SHIFT, 0,
-                               pc->rtce_window_size >> SPAPR_TCE_PAGE_SHIFT); +                               pc->rtce_window_size >> SPAPR_TCE_PAGE_SHIFT,
+                               false);
          dev->tcet->vdev = dev;
          memory_region_add_subregion_overlap(&dev->mrroot, 0,
spapr_tce_get_iommu(dev->tcet), 2);

--
Alexey



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