docs: Move virtio-pmem.rst into the system manual

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

diff --git a/docs/system/index.rst b/docs/system/index.rst
index 0f0f6d2e99d26af09b4cd9658d2fb01bafec43d4..2a5155c67dc84dc13ed8056a1d1edbdb79093fa7 100644 (file)
--- a/docs/system/index.rst
+++ b/docs/system/index.rst
@@ -30,6 +30,7 @@ Contents:
    gdb
    managed-startup
    cpu-hotplug
+   virtio-pmem
    targets
    security
    deprecated

diff --git a/docs/system/virtio-pmem.rst b/docs/system/virtio-pmem.rst
new file mode 100644 (file)
index 0000000..4bf5d00
--- /dev/null
+++ b/docs/system/virtio-pmem.rst
@@ -0,0 +1,76 @@
+
+========================
+QEMU virtio pmem
+========================
+
+ This document explains the setup and usage of the virtio pmem device
+ which is available since QEMU v4.1.0.
+
+ The virtio pmem device is a paravirtualized persistent memory device
+ on regular (i.e non-NVDIMM) storage.
+
+Usecase
+--------
+
+  Virtio pmem allows to bypass the guest page cache and directly use
+  host page cache. This reduces guest memory footprint as the host can
+  make efficient memory reclaim decisions under memory pressure.
+
+o How does virtio-pmem compare to the nvdimm emulation supported by QEMU?
+
+  NVDIMM emulation on regular (i.e. non-NVDIMM) host storage does not
+  persist the guest writes as there are no defined semantics in the device
+  specification. The virtio pmem device provides guest write persistence
+  on non-NVDIMM host storage.
+
+virtio pmem usage
+-----------------
+
+  A virtio pmem device backed by a memory-backend-file can be created on
+  the QEMU command line as in the following example::
+
+    -object memory-backend-file,id=mem1,share,mem-path=./virtio_pmem.img,size=4G
+    -device virtio-pmem-pci,memdev=mem1,id=nv1
+
+  where:
+
+  - "object memory-backend-file,id=mem1,share,mem-path=<image>, size=<image size>"
+    creates a backend file with the specified size.
+
+  - "device virtio-pmem-pci,id=nvdimm1,memdev=mem1" creates a virtio pmem
+    pci device whose storage is provided by above memory backend device.
+
+  Multiple virtio pmem devices can be created if multiple pairs of "-object"
+  and "-device" are provided.
+
+Hotplug
+-------
+
+Virtio pmem devices can be hotplugged via the QEMU monitor. First, the
+memory backing has to be added via 'object_add'; afterwards, the virtio
+pmem device can be added via 'device_add'.
+
+For example, the following commands add another 4GB virtio pmem device to
+the guest::
+
+ (qemu) object_add memory-backend-file,id=mem2,share=on,mem-path=virtio_pmem2.img,size=4G
+ (qemu) device_add virtio-pmem-pci,id=virtio_pmem2,memdev=mem2
+
+Guest Data Persistence
+----------------------
+
+ Guest data persistence on non-NVDIMM requires guest userspace applications
+ to perform fsync/msync. This is different from a real nvdimm backend where
+ no additional fsync/msync is required. This is to persist guest writes in
+ host backing file which otherwise remains in host page cache and there is
+ risk of losing the data in case of power failure.
+
+ With virtio pmem device, MAP_SYNC mmap flag is not supported. This provides
+ a hint to application to perform fsync for write persistence.
+
+Limitations
+------------
+- Real nvdimm device backend is not supported.
+- virtio pmem hotunplug is not supported.
+- ACPI NVDIMM features like regions/namespaces are not supported.
+- ndctl command is not supported.

diff --git a/docs/virtio-pmem.rst b/docs/virtio-pmem.rst
deleted file mode 100644 (file)
index 4bf5d00..0000000
--- a/docs/virtio-pmem.rst
+++ /dev/null
@@ -1,76 +0,0 @@
-
-========================
-QEMU virtio pmem
-========================
-
- This document explains the setup and usage of the virtio pmem device
- which is available since QEMU v4.1.0.
-
- The virtio pmem device is a paravirtualized persistent memory device
- on regular (i.e non-NVDIMM) storage.
-
-Usecase
---------
-
-  Virtio pmem allows to bypass the guest page cache and directly use
-  host page cache. This reduces guest memory footprint as the host can
-  make efficient memory reclaim decisions under memory pressure.
-
-o How does virtio-pmem compare to the nvdimm emulation supported by QEMU?
-
-  NVDIMM emulation on regular (i.e. non-NVDIMM) host storage does not
-  persist the guest writes as there are no defined semantics in the device
-  specification. The virtio pmem device provides guest write persistence
-  on non-NVDIMM host storage.
-
-virtio pmem usage
------------------
-
-  A virtio pmem device backed by a memory-backend-file can be created on
-  the QEMU command line as in the following example::
-
-    -object memory-backend-file,id=mem1,share,mem-path=./virtio_pmem.img,size=4G
-    -device virtio-pmem-pci,memdev=mem1,id=nv1
-
-  where:
-
-  - "object memory-backend-file,id=mem1,share,mem-path=<image>, size=<image size>"
-    creates a backend file with the specified size.
-
-  - "device virtio-pmem-pci,id=nvdimm1,memdev=mem1" creates a virtio pmem
-    pci device whose storage is provided by above memory backend device.
-
-  Multiple virtio pmem devices can be created if multiple pairs of "-object"
-  and "-device" are provided.
-
-Hotplug
--------
-
-Virtio pmem devices can be hotplugged via the QEMU monitor. First, the
-memory backing has to be added via 'object_add'; afterwards, the virtio
-pmem device can be added via 'device_add'.
-
-For example, the following commands add another 4GB virtio pmem device to
-the guest::
-
- (qemu) object_add memory-backend-file,id=mem2,share=on,mem-path=virtio_pmem2.img,size=4G
- (qemu) device_add virtio-pmem-pci,id=virtio_pmem2,memdev=mem2
-
-Guest Data Persistence
-----------------------
-
- Guest data persistence on non-NVDIMM requires guest userspace applications
- to perform fsync/msync. This is different from a real nvdimm backend where
- no additional fsync/msync is required. This is to persist guest writes in
- host backing file which otherwise remains in host page cache and there is
- risk of losing the data in case of power failure.
-
- With virtio pmem device, MAP_SYNC mmap flag is not supported. This provides
- a hint to application to perform fsync for write persistence.
-
-Limitations
-------------
-- Real nvdimm device backend is not supported.
-- virtio pmem hotunplug is not supported.
-- ACPI NVDIMM features like regions/namespaces are not supported.
-- ndctl command is not supported.