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Re: [Qemu-ppc] [PATCH qemu v6 08/15] spapr_iommu: Introduce "enabled" st


From: Alexey Kardashevskiy
Subject: Re: [Qemu-ppc] [PATCH qemu v6 08/15] spapr_iommu: Introduce "enabled" state for TCE table
Date: Wed, 22 Apr 2015 19:10:14 +1000
User-agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0

On 04/22/2015 04:14 PM, David Gibson wrote:
On Sat, Apr 11, 2015 at 01:24:37AM +1000, Alexey Kardashevskiy wrote:
Currently TCE tables are created once at start and their size never
changes. We are going to change that by introducing a Dynamic DMA windows
support where DMA configuration may change during the guest execution.

This changes spapr_tce_new_table() to create an empty stub object. Only
LIOBN is assigned by the time of creation. It still will be called once
at the owner object (VIO or PHB) creation.

This introduces an "enabled" state for TCE table objects with two
helper functions - spapr_tce_table_enable()/spapr_tce_table_disable().
spapr_tce_table_enable() receives TCE table parameters and allocates
a guest view of the TCE table (in the user space or KVM).
spapr_tce_table_disable() disposes the table.

Follow up patches will disable+enable tables on reset (system reset
or DDW reset).

No visible change in behaviour is expected except the actual table
will be reallocated every reset. We might optimize this later.

The other way to implement this would be dynamically create/remove
the TCE table QOM objects but this would make migration impossible
as migration expects all QOM objects to exist at the receiver
so we have to have TCE table objects created when migration begins.

Signed-off-by: Alexey Kardashevskiy <address@hidden>
---
Changes:
v6:
* got rid of set_props()
---
  hw/ppc/spapr_iommu.c    | 104 +++++++++++++++++++++++++++++++-----------------
  hw/ppc/spapr_pci.c      |  16 +++++---
  hw/ppc/spapr_pci_vfio.c |  10 ++---
  hw/ppc/spapr_vio.c      |   9 ++---
  include/hw/ppc/spapr.h  |  11 ++---
  5 files changed, 93 insertions(+), 57 deletions(-)

diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
index a14cdc4..64f20f2 100644
--- a/hw/ppc/spapr_iommu.c
+++ b/hw/ppc/spapr_iommu.c
@@ -126,8 +126,47 @@ static MemoryRegionIOMMUOps spapr_iommu_ops = {
  static int spapr_tce_table_realize(DeviceState *dev)
  {
      sPAPRTCETable *tcet = SPAPR_TCE_TABLE(dev);
+
+    QLIST_INSERT_HEAD(&spapr_tce_tables, tcet, list);
+
+    vmstate_register(DEVICE(tcet), tcet->liobn, &vmstate_spapr_tce_table,
+                     tcet);
+
+    return 0;
+}
+
+sPAPRTCETable *spapr_tce_new_table(DeviceState *owner, uint32_t liobn)
+{
+    sPAPRTCETable *tcet;
+    char tmp[64];
+
+    if (spapr_tce_find_by_liobn(liobn)) {
+        fprintf(stderr, "Attempted to create TCE table with duplicate"
+                " LIOBN 0x%x\n", liobn);
+        return NULL;
+    }
+
+    tcet = SPAPR_TCE_TABLE(object_new(TYPE_SPAPR_TCE_TABLE));
+    tcet->liobn = liobn;
+
+    snprintf(tmp, sizeof(tmp), "tce-table-%x", liobn);
+    object_property_add_child(OBJECT(owner), tmp, OBJECT(tcet), NULL);
+
+    object_property_set_bool(OBJECT(tcet), true, "realized", NULL);
+
+    trace_spapr_iommu_new_table(tcet->liobn, tcet, tcet->table, tcet->fd);
+
+    return tcet;
+}
+
+static void spapr_tce_table_do_enable(sPAPRTCETable *tcet)

AFAICT there's only one caller of this, so it's not clear why this
isn't just open-coded in spapr_tce_table_enable().


There is another call in "[PATCH qemu v6 14/15] spapr_pci/spapr_pci_vfio: Support Dynamic DMA Windows (DDW)", in spapr_tce_table_post_load().

Should I put a note in the commit log?


--
Alexey



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