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From b872c9566d3f18b4d6580a7b271bbbc21c026a36 Mon Sep 17 00:00:00 2001
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From: "plai@redhat.com" <plai@redhat.com>
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Date: Mon, 7 Jan 2019 17:02:19 +0000
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Subject: [PATCH 18/22] hostmem-file: add the 'pmem' option
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RH-Author: plai@redhat.com
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Message-id: <1546880543-24860-7-git-send-email-plai@redhat.com>
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Patchwork-id: 83892
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O-Subject: [RHEL8.0 qemu-kvm PATCH v7 06/10] hostmem-file: add the 'pmem' option
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Bugzilla: 1539285
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>
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From: Junyan He <junyan.he@intel.com>
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When QEMU emulates vNVDIMM labels and migrates vNVDIMM devices, it
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needs to know whether the backend storage is a real persistent memory,
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in order to decide whether special operations should be performed to
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ensure the data persistence.
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This boolean option 'pmem' allows users to specify whether the backend
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storage of memory-backend-file is a real persistent memory. If
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'pmem=on', QEMU will set the flag RAM_PMEM in the RAM block of the
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corresponding memory region. If 'pmem' is set while lack of libpmem
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support, a error is generated.
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Signed-off-by: Junyan He <junyan.he@intel.com>
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Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
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Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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Reviewed-by: Igor Mammedov <imammedo@redhat.com>
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Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
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Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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(cherry picked from commit a4de8552b2580adf6fa4874439217b65d3bdd88b)
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Signed-off-by: Paul Lai <plai@redhat.com>
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Resolved Conflicts:
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	docs/nvdimm.txt
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 backends/hostmem-file.c | 43 +++++++++++++++++++++++++++++++++++++++++--
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 docs/nvdimm.txt         | 42 ++++++++++++++++++++++++++++++++++++++++++
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 exec.c                  |  8 ++++++++
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 include/exec/memory.h   |  4 ++++
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 include/exec/ram_addr.h |  3 +++
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 qemu-options.hx         |  7 +++++++
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 6 files changed, 105 insertions(+), 2 deletions(-)
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diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
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index 34c68bb..2476dcb 100644
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--- a/backends/hostmem-file.c
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+++ b/backends/hostmem-file.c
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@@ -12,6 +12,7 @@
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 #include "qemu/osdep.h"
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 #include "qapi/error.h"
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 #include "qemu-common.h"
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+#include "qemu/error-report.h"
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 #include "sysemu/hostmem.h"
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 #include "sysemu/sysemu.h"
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 #include "qom/object_interfaces.h"
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@@ -31,9 +32,10 @@ typedef struct HostMemoryBackendFile HostMemoryBackendFile;
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 struct HostMemoryBackendFile {
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     HostMemoryBackend parent_obj;
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-    bool discard_data;
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     char *mem_path;
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     uint64_t align;
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+    bool discard_data;
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+    bool is_pmem;
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 };
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 static void
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@@ -59,7 +61,8 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
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         memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),
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                                  path,
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                                  backend->size, fb->align,
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-                                 backend->share ? RAM_SHARED : 0,
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+                                 (backend->share ? RAM_SHARED : 0) |
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+                                 (fb->is_pmem ? RAM_PMEM : 0),
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                                  fb->mem_path, errp);
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         g_free(path);
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     }
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@@ -131,6 +134,39 @@ static void file_memory_backend_set_align(Object *o, Visitor *v,
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     error_propagate(errp, local_err);
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 }
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+static bool file_memory_backend_get_pmem(Object *o, Error **errp)
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+{
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+    return MEMORY_BACKEND_FILE(o)->is_pmem;
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+}
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+
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+static void file_memory_backend_set_pmem(Object *o, bool value, Error **errp)
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+{
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+    HostMemoryBackend *backend = MEMORY_BACKEND(o);
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+    HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
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+
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+    if (host_memory_backend_mr_inited(backend)) {
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+        error_setg(errp, "cannot change property 'pmem' of %s '%s'",
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+                   object_get_typename(o),
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+                   object_get_canonical_path_component(o));
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+        return;
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+    }
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+
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+#ifndef CONFIG_LIBPMEM
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+    if (value) {
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+        Error *local_err = NULL;
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+        error_setg(&local_err,
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+                   "Lack of libpmem support while setting the 'pmem=on'"
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+                   " of %s '%s'. We can't ensure data persistence.",
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+                   object_get_typename(o),
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+                   object_get_canonical_path_component(o));
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+        error_propagate(errp, local_err);
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+        return;
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+    }
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+#endif
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+
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+    fb->is_pmem = value;
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+}
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+
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 static void file_backend_unparent(Object *obj)
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 {
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     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
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@@ -162,6 +198,9 @@ file_backend_class_init(ObjectClass *oc, void *data)
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         file_memory_backend_get_align,
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         file_memory_backend_set_align,
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         NULL, NULL, &error_abort);
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+    object_class_property_add_bool(oc, "pmem",
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+        file_memory_backend_get_pmem, file_memory_backend_set_pmem,
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+        &error_abort);
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 }
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 static void file_backend_instance_finalize(Object *o)
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diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt
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index e903d8b..5f158a6 100644
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--- a/docs/nvdimm.txt
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+++ b/docs/nvdimm.txt
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@@ -153,3 +153,45 @@ guest NVDIMM region mapping structure.  This unarmed flag indicates
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 guest software that this vNVDIMM device contains a region that cannot
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 accept persistent writes. In result, for example, the guest Linux
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 NVDIMM driver, marks such vNVDIMM device as read-only.
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+
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+NVDIMM Persistence
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+------------------
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+
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+ACPI 6.2 Errata A added support for a new Platform Capabilities Structure
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+which allows the platform to communicate what features it supports related to
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+NVDIMM data persistence.  Users can provide a persistence value to a guest via
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+the optional "nvdimm-persistence" machine command line option:
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+
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+    -machine pc,accel=kvm,nvdimm,nvdimm-persistence=cpu
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+
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+There are currently two valid values for this option:
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+
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+"mem-ctrl" - The platform supports flushing dirty data from the memory
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+             controller to the NVDIMMs in the event of power loss.
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+
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+"cpu"      - The platform supports flushing dirty data from the CPU cache to
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+             the NVDIMMs in the event of power loss.  This implies that the
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+             platform also supports flushing dirty data through the memory
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+             controller on power loss.
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+
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+If the vNVDIMM backend is in host persistent memory that can be accessed in
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+SNIA NVM Programming Model [1] (e.g., Intel NVDIMM), it's suggested to set
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+the 'pmem' option of memory-backend-file to 'on'. When 'pmem' is 'on' and QEMU
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+is built with libpmem [2] support (configured with --enable-libpmem), QEMU
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+will take necessary operations to guarantee the persistence of its own writes
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+to the vNVDIMM backend(e.g., in vNVDIMM label emulation and live migration).
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+If 'pmem' is 'on' while there is no libpmem support, qemu will exit and report
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+a "lack of libpmem support" message to ensure the persistence is available.
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+For example, if we want to ensure the persistence for some backend file,
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+use the QEMU command line:
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+
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+    -object memory-backend-file,id=nv_mem,mem-path=/XXX/yyy,size=4G,pmem=on
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+
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+References
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+----------
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+
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+[1] NVM Programming Model (NPM)
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+	Version 1.2
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+    https://www.snia.org/sites/default/files/technical_work/final/NVMProgrammingModel_v1.2.pdf
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+[2] Persistent Memory Development Kit (PMDK), formerly known as NVML project, home page:
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+    http://pmem.io/pmdk/
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diff --git a/exec.c b/exec.c
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index 8d58e8f..9028700 100644
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--- a/exec.c
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+++ b/exec.c
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@@ -2049,6 +2049,9 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
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     Error *local_err = NULL;
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     int64_t file_size;
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+    /* Just support these ram flags by now. */
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+    assert((ram_flags & ~(RAM_SHARED | RAM_PMEM)) == 0);
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+
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     if (xen_enabled()) {
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         error_setg(errp, "-mem-path not supported with Xen");
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         return NULL;
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@@ -3867,6 +3870,11 @@ err:
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     return ret;
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 }
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+bool ramblock_is_pmem(RAMBlock *rb)
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+{
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+    return rb->flags & RAM_PMEM;
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+}
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+
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 #endif
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 void page_size_init(void)
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diff --git a/include/exec/memory.h b/include/exec/memory.h
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index b3abe61..fd2c574 100644
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--- a/include/exec/memory.h
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+++ b/include/exec/memory.h
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@@ -122,6 +122,9 @@ typedef struct IOMMUNotifier IOMMUNotifier;
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 /* RAM can be migrated */
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 #define RAM_MIGRATABLE (1 << 4)
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+/* RAM is a persistent kind memory */
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+#define RAM_PMEM (1 << 5)
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+
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 static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn,
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                                        IOMMUNotifierFlag flags,
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                                        hwaddr start, hwaddr end)
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@@ -541,6 +544,7 @@ void memory_region_init_resizeable_ram(MemoryRegion *mr,
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  *         (getpagesize()) will be used.
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  * @ram_flags: Memory region features:
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  *             - RAM_SHARED: memory must be mmaped with the MAP_SHARED flag
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+ *             - RAM_PMEM: the memory is persistent memory
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  *             Other bits are ignored now.
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  * @path: the path in which to allocate the RAM.
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  * @errp: pointer to Error*, to store an error if it happens.
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diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
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index 67e163e..922305d 100644
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--- a/include/exec/ram_addr.h
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+++ b/include/exec/ram_addr.h
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@@ -70,6 +70,8 @@ static inline unsigned long int ramblock_recv_bitmap_offset(void *host_addr,
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     return host_addr_offset >> TARGET_PAGE_BITS;
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 }
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+bool ramblock_is_pmem(RAMBlock *rb);
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+
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 long qemu_getrampagesize(void);
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 unsigned long last_ram_page(void);
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@@ -84,6 +86,7 @@ unsigned long last_ram_page(void);
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  *  @ram_flags: specify the properties of the ram block, which can be one
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  *              or bit-or of following values
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  *              - RAM_SHARED: mmap the backing file or device with MAP_SHARED
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+ *              - RAM_PMEM: the backend @mem_path or @fd is persistent memory
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  *              Other bits are ignored.
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  *  @mem_path or @fd: specify the backing file or device
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  *  @errp: pointer to Error*, to store an error if it happens
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diff --git a/qemu-options.hx b/qemu-options.hx
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index 683ab0d..1b6786b 100644
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--- a/qemu-options.hx
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+++ b/qemu-options.hx
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@@ -4051,6 +4051,13 @@ requires an alignment different than the default one used by QEMU, eg
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 the device DAX /dev/dax0.0 requires 2M alignment rather than 4K. In
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 such cases, users can specify the required alignment via this option.
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+The @option{pmem} option specifies whether the backing file specified
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+by @option{mem-path} is in host persistent memory that can be accessed
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+using the SNIA NVM programming model (e.g. Intel NVDIMM).
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+If @option{pmem} is set to 'on', QEMU will take necessary operations to
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+guarantee the persistence of its own writes to @option{mem-path}
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+(e.g. in vNVDIMM label emulation and live migration).
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+
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 @item -object memory-backend-ram,id=@var{id},merge=@var{on|off},dump=@var{on|off},share=@var{on|off},prealloc=@var{on|off},size=@var{size},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave}
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 Creates a memory backend object, which can be used to back the guest RAM.
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-- 
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1.8.3.1
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