[Qemu-devel] [RFC PATCH qemu 1/4] memory: Add reporting of supported page sizes

[Alexey Kardashevskiy <aik@ozlabs.ru>]

Every IOMMU has some granularity which MemoryRegionIOMMUOps::translate
uses when translating, however this information is not available outside
the translate context for various checks.

This adds a get_page_sizes callback to MemoryRegionIOMMUOps and
a wrapper for it so IOMMU users (such as VFIO) can know the actual
page size(s) used by an IOMMU.

The qemu_real_host_page_mask is used as fallback.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
Changes:
v4:
* s/1<<TARGET_PAGE_BITS/qemu_real_host_page_size/
---
 hw/ppc/spapr_iommu.c  |  8 ++++++++
 include/exec/memory.h | 11 +++++++++++
 memory.c              |  9 +++++++++
 3 files changed, 28 insertions(+)

diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
index f61504e..a2572c4 100644
--- a/hw/ppc/spapr_iommu.c
+++ b/hw/ppc/spapr_iommu.c
@@ -104,6 +104,13 @@ static IOMMUTLBEntry spapr_tce_translate_iommu(MemoryRegion *iommu, hwaddr addr,
     return ret;
 }
 
+static uint64_t spapr_tce_get_page_sizes(MemoryRegion *iommu)
+{
+    sPAPRTCETable *tcet = container_of(iommu, sPAPRTCETable, iommu);
+
+    return 1ULL << tcet->page_shift;
+}
+
 static int spapr_tce_table_post_load(void *opaque, int version_id)
 {
     sPAPRTCETable *tcet = SPAPR_TCE_TABLE(opaque);
@@ -135,6 +142,7 @@ static const VMStateDescription vmstate_spapr_tce_table = {
 
 static MemoryRegionIOMMUOps spapr_iommu_ops = {
     .translate = spapr_tce_translate_iommu,
+    .get_page_sizes = spapr_tce_get_page_sizes,
 };
 
 static int spapr_tce_table_realize(DeviceState *dev)
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 1394715..dc90403 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -150,6 +150,8 @@ struct MemoryRegionOps {
 typedef struct MemoryRegionIOMMUOps MemoryRegionIOMMUOps;
 
 struct MemoryRegionIOMMUOps {
+    /* Returns supported page sizes */
+    uint64_t (*get_page_sizes)(MemoryRegion *iommu);
     /* Return a TLB entry that contains a given address. */
     IOMMUTLBEntry (*translate)(MemoryRegion *iommu, hwaddr addr, bool is_write);
 };
@@ -552,6 +554,15 @@ static inline bool memory_region_is_romd(MemoryRegion *mr)
 bool memory_region_is_iommu(MemoryRegion *mr);
 
 /**
+ * memory_region_iommu_get_page_sizes: get supported page sizes in an iommu
+ *
+ * Returns %bitmap of supported page sizes for an iommu.
+ *
+ * @mr: the memory region being queried
+ */
+uint64_t memory_region_iommu_get_page_sizes(MemoryRegion *mr);
+
+/**
  * memory_region_notify_iommu: notify a change in an IOMMU translation entry.
  *
  * @mr: the memory region that was changed
diff --git a/memory.c b/memory.c
index 5a0cc66..eec3746 100644
--- a/memory.c
+++ b/memory.c
@@ -1413,6 +1413,15 @@ bool memory_region_is_iommu(MemoryRegion *mr)
     return mr->iommu_ops;
 }
 
+uint64_t memory_region_iommu_get_page_sizes(MemoryRegion *mr)
+{
+    assert(memory_region_is_iommu(mr));
+    if (mr->iommu_ops && mr->iommu_ops->get_page_sizes) {
+        return mr->iommu_ops->get_page_sizes(mr);
+    }
+    return qemu_real_host_page_size;
+}
+
 void memory_region_register_iommu_notifier(MemoryRegion *mr, Notifier *n)
 {
     notifier_list_add(&mr->iommu_notify, n);
-- 
2.4.0.rc3.8.gfb3e7d5