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Re: [Qemu-devel] [RFC PATCH qemu v3 1/4] memory: Add reporting of suppor


From: Alexey Kardashevskiy
Subject: Re: [Qemu-devel] [RFC PATCH qemu v3 1/4] memory: Add reporting of supported page sizes
Date: Thu, 16 Jul 2015 11:12:29 +1000
User-agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0

On 07/16/2015 04:26 AM, Alex Williamson wrote:
On Tue, 2015-07-14 at 22:21 +1000, Alexey Kardashevskiy wrote:
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.

TARGET_PAGE_BITS shift is used as fallback.

Signed-off-by: Alexey Kardashevskiy <address@hidden>
---
  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..9ca74e3 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -152,6 +152,8 @@ typedef struct MemoryRegionIOMMUOps MemoryRegionIOMMUOps;
  struct MemoryRegionIOMMUOps {
      /* Return a TLB entry that contains a given address. */
      IOMMUTLBEntry (*translate)(MemoryRegion *iommu, hwaddr addr, bool 
is_write);
+    /* Returns supported page sizes */
+    uint64_t (*get_page_sizes)(MemoryRegion *iommu);
  };

  typedef struct CoalescedMemoryRange CoalescedMemoryRange;
@@ -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..0732763 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 1ULL << TARGET_PAGE_BITS;

At this rate we're adding TARGET_PAGE_foo faster than Peter can remove
them.


Well, returning zero is better? Or qemu_real_host_page_size?



--
Alexey



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