Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic

[Paolo Bonzini <pbonzini@redhat.com>]

> So how about:
>  MemoryRegionSection memory_region_find(MemoryRegion *address_space,
>                                        hwaddr addr, uint64_t size);
> becomes
>  MemoryRegionSection address_space_find_region_by_addr(
>                                        AddressSpace *address_space,
>                                        hwaddr addr, uint64_t size);
> (bit of a mouthful, but never mind)
> 
>  void memory_global_sync_dirty_bitmap(MemoryRegion *address_space);
> becomes
>  void address_space_sync_dirty_bitmap(AddressSpace *address_space);

I think the latter makes definite sense, I am not quite as sure about the
former.

Looking at framebuffer.c's use of memory_region_find, here you really want
to go from the "local" view to a global one in order to look at global
data structures such as the dirty bitmap.  So it is right to have
memory_region_find as a MemoryRegion operation, even though right now
it is always passed an AddressSpace.

Communicating the absolute address to KVM is another example of
this local->global translation.  Hence, my suggestion is to remove
memory_region_find's limitation on the first argument, and make it work
on nested regions too.  With this change, memory_region_find() nicely
fits Igor's use case.

Not coincidentially, the additional code in memory_region_find() is
very similar to Igor's memory_region_get_address().

See the attached patch, which I tested on master.  Igor, can you try it
with iccbus?

Paolo

-------------- 8< --------------------
>From 953460fa8ee9f9e7243ea34eb57a901102be9307 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Tue, 23 Apr 2013 10:29:51 +0200
Subject: [RFC PATCH 17/21] extend memory_region_find() and use it in kvm/ioapic

kvm/ioapic is relying on the fact that SysBus device
maps mmio regions with offset counted from start of system memory.
But if ioapic's region is moved to another sub-region which doesn't
start at the beginning of system memory then using offset isn't correct.

To fix kvm/ioapic, extend memory_region_find() so that it can help
retrieving the absolute region address and the respective address space.

The patch is a no-op in case mr is parentless, i.e. mr->addr == 0
and mr->parent == NULL.

Based on a patch by Igor Mammedov. <imammedo@redhat.com>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/i386/kvm/ioapic.c  |    9 ++++++++-
 include/exec/memory.h |   13 +++++++------
 memory.c              |   19 ++++++++++++++-----
 3 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/hw/i386/kvm/ioapic.c b/hw/i386/kvm/ioapic.c
index a3bd519..7564d07 100644
--- a/hw/i386/kvm/ioapic.c
+++ b/hw/i386/kvm/ioapic.c
@@ -89,14 +89,21 @@ static void kvm_ioapic_put(IOAPICCommonState *s)
 {
     struct kvm_irqchip chip;
     struct kvm_ioapic_state *kioapic;
+    MemoryRegionSection mrs;
     int ret, i;
 
+    mrs = memory_region_find(&s->io_memory, 0, 0x1000);
+    if (mrs.mr != &s->io_memory || mrs.offset_within_region != 0) {
+        fprintf(stderr, "cannot find IOAPIC base\n");
+        abort();
+    }
+
     chip.chip_id = KVM_IRQCHIP_IOAPIC;
     kioapic = &chip.chip.ioapic;
 
     kioapic->id = s->id;
     kioapic->ioregsel = s->ioregsel;
-    kioapic->base_address = s->busdev.mmio[0].addr;
+    kioapic->base_address = mrs.offset_within_address_space;
     kioapic->irr = s->irr;
     for (i = 0; i < IOAPIC_NUM_PINS; i++) {
         kioapic->redirtbl[i].bits = s->ioredtbl[i];
diff --git a/include/exec/memory.h b/include/exec/memory.h
index eb9e659..5854d19 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -725,17 +725,18 @@ void memory_region_set_alias_offset(MemoryRegion *mr,
  *
  * Returns a #MemoryRegionSection that describes a contiguous overlap.
  * It will have the following characteristics:
- *    .@offset_within_address_space >= @addr
- *    .@offset_within_address_space + .@size <= @addr + @size
  *    .@size = 0 iff no overlap was found
  *    .@mr is non-%NULL iff an overlap was found
  *
- * @address_space: a top-level (i.e. parentless) region that contains
- *       the region to be found
- * @addr: start of the area within @address_space to be searched
+ * If @mr is parent-less,
+ *    .@offset_within_address_space >= @addr
+ *    .@offset_within_address_space + .@size <= @addr + @size
+ *
+ * @mr: a (possibly indirect) parent that contains the region to be found
+ * @addr: start of the area within @as to be searched
  * @size: size of the area to be searched
  */
-MemoryRegionSection memory_region_find(MemoryRegion *address_space,
+MemoryRegionSection memory_region_find(MemoryRegion *mr,
                                        hwaddr addr, uint64_t size);
 
 /**
diff --git a/memory.c b/memory.c
index c82bd12..dba0a4b 100644
--- a/memory.c
+++ b/memory.c
@@ -1451,15 +1451,24 @@ static FlatRange *address_space_lookup(AddressSpace *as, AddrRange addr)
                    sizeof(FlatRange), cmp_flatrange_addr);
 }
 
-MemoryRegionSection memory_region_find(MemoryRegion *address_space,
+MemoryRegionSection memory_region_find(MemoryRegion *mr,
                                        hwaddr addr, uint64_t size)
 {
-    AddressSpace *as = memory_region_to_address_space(address_space);
-    AddrRange range = addrrange_make(int128_make64(addr),
-                                     int128_make64(size));
-    FlatRange *fr = address_space_lookup(as, range);
     MemoryRegionSection ret = { .mr = NULL, .size = 0 };
+    MemoryRegion *root;
+    AddressSpace *as;
+    AddrRange range;
+    FlatRange *fr;
+
+    addr += mr->addr;
+    for (root = mr; root->parent; ) {
+        root = root->parent;
+        addr += root->addr;
+    }
 
+    as = memory_region_to_address_space(root);
+    range = addrrange_make(int128_make64(addr), int128_make64(size));
+    fr = address_space_lookup(as, range);
     if (!fr) {
         return ret;
     }
-- 
1.7.1