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Re: [Qemu-devel] [RFC v1] Add declarations for hierarchical memory regio


From: Anthony Liguori
Subject: Re: [Qemu-devel] [RFC v1] Add declarations for hierarchical memory region API
Date: Thu, 19 May 2011 15:43:41 -0500
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110424 Lightning/1.0b2 Thunderbird/3.1.10

On 05/19/2011 09:12 AM, Avi Kivity wrote:
The memory API separates the attributes of a memory region (its size, how
reads or writes are handled, dirty logging, and coalescing) from where it
is mapped and whether it is enabled.  This allows a device to configure
a memory region once, then hand it off to its parent bus to map it according
to the bus configuration.

Hierarchical registration also allows a device to compose a region out of
a number of sub-regions with different properties; for example some may be
RAM while others may be MMIO.

Signed-off-by: Avi Kivity<address@hidden>
---
  memory.h |  142 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  1 files changed, 142 insertions(+), 0 deletions(-)
  create mode 100644 memory.h

diff --git a/memory.h b/memory.h
new file mode 100644
index 0000000..77c5951
--- /dev/null
+++ b/memory.h
@@ -0,0 +1,142 @@
+#ifndef MEMORY_H
+#define MEMORY_H
+
+#include<stdint.h>
+#include<stdbool.h>
+#include "qemu-common.h"
+#include "cpu-common.h"
+#include "targphys.h"
+#include "qemu-queue.h"
+
+typedef struct MemoryRegionOps MemoryRegionOps;
+typedef struct MemoryRegion MemoryRegion;
+
+/*
+ * Memory region callbacks
+ */
+struct MemoryRegionOps {
+    /* Read from the memory region. @addr is relative to @mr; @size is
+     * in bytes. */
+    uint64_t (*read)(MemoryRegion *mr,
+                     target_phys_addr_t addr,
+                     unsigned size);
+    /* Write to the memory region. @addr is relative to @mr; @size is
+     * in bytes. */
+    void (*write)(MemoryRegion *mr,
+                  target_phys_addr_t addr,
+                  uint64_t data,
+                  unsigned size);
+    /* Guest-visible constraints: */
+    struct {
+        /* If nonzero, specify bounds on access sizes beyond which a machine
+         * check is thrown.
+         */
+        unsigned min_access_size;
+        unsigned max_access_size;
+        /* If true, unaligned accesses are supported.  Otherwise unaligned
+         * accesses throw machine checks.
+         */
+         bool unaligned;
+    } valid;

Under what circumstances would this be used?

The behavior of devices that receive non-natural accesses varies wildly.

For PCI devices, invalid accesses almost always return ~0. I can't think of a device where an MCE would occur.

Regards,

Anthony Liguori



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