| Message ID | 1528784900-7310-4-git-send-email-junyan.he@gmx.com |
|---|---|
| State | New |
| Headers | show |
| Series | nvdimm: guarantee persistence of QEMU writes to persistent memory | expand |
On Tue, 12 Jun 2018 14:28:16 +0800 junyan.he@gmx.com wrote: > From: Junyan He <junyan.he@intel.com> > > When QEMU emulates vNVDIMM labels and migrates vNVDIMM devices, it > needs to know whether the backend storage is a real persistent memory, > in order to decide whether special operations should be performed to > ensure the data persistence. > > This boolean option 'pmem' allows users to specify whether the backend > storage of memory-backend-file is a real persistent memory. If > 'pmem=on', QEMU will set the flag RAM_PMEM in the RAM block of the > corresponding memory region. > As were noted in v6 by Eduardo and me, we would prefer that pmem=on would fail if qemu is built without libpmem support. > Signed-off-by: Junyan He <junyan.he@intel.com> > Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com> > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> > --- > backends/hostmem-file.c | 27 ++++++++++++++++++++++++++- > docs/nvdimm.txt | 18 ++++++++++++++++++ > exec.c | 9 +++++++++ > include/exec/memory.h | 4 ++++ > include/exec/ram_addr.h | 3 +++ > qemu-options.hx | 7 +++++++ > 6 files changed, 67 insertions(+), 1 deletion(-) > > diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c > index 34c68bb..6a861f0 100644 > --- a/backends/hostmem-file.c > +++ b/backends/hostmem-file.c > @@ -34,6 +34,7 @@ struct HostMemoryBackendFile { > bool discard_data; > char *mem_path; > uint64_t align; > + bool is_pmem; > }; > > static void > @@ -59,7 +60,8 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) > memory_region_init_ram_from_file(&backend->mr, OBJECT(backend), > path, > backend->size, fb->align, > - backend->share ? RAM_SHARED : 0, > + (backend->share ? RAM_SHARED : 0) | > + (fb->is_pmem ? RAM_PMEM : 0), > fb->mem_path, errp); > g_free(path); > } > @@ -131,6 +133,26 @@ static void file_memory_backend_set_align(Object *o, Visitor *v, > error_propagate(errp, local_err); > } > > +static bool file_memory_backend_get_pmem(Object *o, Error **errp) > +{ > + return MEMORY_BACKEND_FILE(o)->is_pmem; > +} > + > +static void file_memory_backend_set_pmem(Object *o, bool value, Error **errp) > +{ > + HostMemoryBackend *backend = MEMORY_BACKEND(o); > + HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o); > + > + if (host_memory_backend_mr_inited(backend)) { > + error_setg(errp, "cannot change property 'pmem' of %s '%s'", > + object_get_typename(o), > + object_get_canonical_path_component(o)); > + return; > + } > + > + fb->is_pmem = value; > +} > + > static void file_backend_unparent(Object *obj) > { > HostMemoryBackend *backend = MEMORY_BACKEND(obj); > @@ -162,6 +184,9 @@ file_backend_class_init(ObjectClass *oc, void *data) > file_memory_backend_get_align, > file_memory_backend_set_align, > NULL, NULL, &error_abort); > + object_class_property_add_bool(oc, "pmem", > + file_memory_backend_get_pmem, file_memory_backend_set_pmem, > + &error_abort); > } > > static void file_backend_instance_finalize(Object *o) > diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt > index 8b48fb4..2f7d348 100644 > --- a/docs/nvdimm.txt > +++ b/docs/nvdimm.txt > @@ -180,3 +180,21 @@ supports CPU Cache Flush and Memory Controller Flush on Power Loss, etc. > > For a complete list of the flags available and for more detailed descriptions, > please consult the ACPI spec. > + > +guest software that this vNVDIMM device contains a region that cannot > +accept persistent writes. In result, for example, the guest Linux > +NVDIMM driver, marks such vNVDIMM device as read-only. > + > +If the vNVDIMM backend is on the host persistent memory that can be > +accessed in SNIA NVM Programming Model [1] (e.g., Intel NVDIMM), it's > +suggested to set the 'pmem' option of memory-backend-file to 'on'. When > +'pmem=on' and QEMU is built with libpmem [2] support (configured with > +--enable-libpmem), QEMU will take necessary operations to guarantee > +the persistence of its own writes to the vNVDIMM backend (e.g., in > +vNVDIMM label emulation and live migration). > + > +References > +---------- > + > +[1] SNIA NVM Programming Model: https://www.snia.org/sites/default/files/technical_work/final/NVMProgrammingModel_v1.2.pdf > +[2] PMDK: http://pmem.io/pmdk/ > diff --git a/exec.c b/exec.c > index 8e079df..c42483e 100644 > --- a/exec.c > +++ b/exec.c > @@ -2077,6 +2077,9 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, > Error *local_err = NULL; > int64_t file_size; > > + /* Just support these ram flags by now. */ > + assert(ram_flags == 0 || (ram_flags & (RAM_SHARED | RAM_PMEM))); > + > if (xen_enabled()) { > error_setg(errp, "-mem-path not supported with Xen"); > return NULL; > @@ -4007,6 +4010,11 @@ err: > return ret; > } > > +bool ramblock_is_pmem(RAMBlock *rb) > +{ > + return rb->flags & RAM_PMEM; > +} > + > #endif > > void page_size_init(void) > @@ -4105,3 +4113,4 @@ void mtree_print_dispatch(fprintf_function mon, void *f, > } > > #endif > + > diff --git a/include/exec/memory.h b/include/exec/memory.h > index 3769c06..7dd43b0 100644 > --- a/include/exec/memory.h > +++ b/include/exec/memory.h > @@ -122,6 +122,9 @@ typedef struct IOMMUNotifier IOMMUNotifier; > /* RAM can be migrated */ > #define RAM_MIGRATABLE (1 << 4) > > +/* RAM is a persistent kind memory */ > +#define RAM_PMEM (1 << 5) > + > static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn, > IOMMUNotifierFlag flags, > hwaddr start, hwaddr end) > @@ -613,6 +616,7 @@ void memory_region_init_resizeable_ram(MemoryRegion *mr, > * (getpagesize()) will be used. > * @ram_flags: Memory region features: > * - RAM_SHARED: memory must be mmaped with the MAP_SHARED flag > + * - RAM_PMEM: the memory is persistent memory > * Other bits are ignored now. > * @path: the path in which to allocate the RAM. > * @errp: pointer to Error*, to store an error if it happens. > diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h > index 5545cf3..3c65643 100644 > --- a/include/exec/ram_addr.h > +++ b/include/exec/ram_addr.h > @@ -70,6 +70,8 @@ static inline unsigned long int ramblock_recv_bitmap_offset(void *host_addr, > return host_addr_offset >> TARGET_PAGE_BITS; > } > > +bool ramblock_is_pmem(RAMBlock *rb); > + > long qemu_getrampagesize(void); > unsigned long last_ram_page(void); > > @@ -84,6 +86,7 @@ unsigned long last_ram_page(void); > * @ram_flags: specify the properties of the ram block, which can be one > * or bit-or of following values > * - RAM_SHARED: mmap the backing file or device with MAP_SHARED > + * - RAM_PMEM: the backend @mem_path or @fd is persistent memory > * Other bits are ignored. > * @mem_path or @fd: specify the backing file or device > * @errp: pointer to Error*, to store an error if it happens > diff --git a/qemu-options.hx b/qemu-options.hx > index c0d3951..006ca44 100644 > --- a/qemu-options.hx > +++ b/qemu-options.hx > @@ -4045,6 +4045,13 @@ requires an alignment different than the default one used by QEMU, eg > the device DAX /dev/dax0.0 requires 2M alignment rather than 4K. In > such cases, users can specify the required alignment via this option. > > +The @option{pmem} option specifies whether the backing file specified > +by @option{mem-path} is on the persistent memory that can be accessed > +using the SNIA NVM programming model (e.g. Intel NVDIMM). > +If @option{pmem}, QEMU will take necessary operations to > +guarantee the persistence of its own writes to @option{mem-path} > +(e.g. in vNVDIMM label emulation and live migration). > + > @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} > > Creates a memory backend object, which can be used to back the guest RAM.
Have already resent this, make qemu exit when meet this, please help to check, thanks -----Original Message----- From: Igor Mammedov [mailto:imammedo@redhat.com] Sent: Friday, June 15, 2018 5:04 PM To: junyan.he@gmx.com Cc: qemu-devel@nongnu.org; Haozhong Zhang <haozhong.zhang@intel.com>; xiaoguangrong.eric@gmail.com; crosthwaite.peter@gmail.com; mst@redhat.com; dgilbert@redhat.com; ehabkost@redhat.com; quintela@redhat.com; He, Junyan <junyan.he@intel.com>; stefanha@redhat.com; pbonzini@redhat.com; rth@twiddle.net Subject: Re: [Qemu-devel] [PATCH 3/7 V7] hostmem-file: add the 'pmem' option On Tue, 12 Jun 2018 14:28:16 +0800 junyan.he@gmx.com wrote: > From: Junyan He <junyan.he@intel.com> > > When QEMU emulates vNVDIMM labels and migrates vNVDIMM devices, it > needs to know whether the backend storage is a real persistent memory, > in order to decide whether special operations should be performed to > ensure the data persistence. > > This boolean option 'pmem' allows users to specify whether the backend > storage of memory-backend-file is a real persistent memory. If > 'pmem=on', QEMU will set the flag RAM_PMEM in the RAM block of the > corresponding memory region. > As were noted in v6 by Eduardo and me, we would prefer that pmem=on would fail if qemu is built without libpmem support. > Signed-off-by: Junyan He <junyan.he@intel.com> > Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com> > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> > --- > backends/hostmem-file.c | 27 ++++++++++++++++++++++++++- > docs/nvdimm.txt | 18 ++++++++++++++++++ > exec.c | 9 +++++++++ > include/exec/memory.h | 4 ++++ > include/exec/ram_addr.h | 3 +++ > qemu-options.hx | 7 +++++++ > 6 files changed, 67 insertions(+), 1 deletion(-) > > diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c index > 34c68bb..6a861f0 100644 > --- a/backends/hostmem-file.c > +++ b/backends/hostmem-file.c > @@ -34,6 +34,7 @@ struct HostMemoryBackendFile { > bool discard_data; > char *mem_path; > uint64_t align; > + bool is_pmem; > }; > > static void > @@ -59,7 +60,8 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) > memory_region_init_ram_from_file(&backend->mr, OBJECT(backend), > path, > backend->size, fb->align, > - backend->share ? RAM_SHARED : 0, > + (backend->share ? RAM_SHARED : 0) | > + (fb->is_pmem ? RAM_PMEM : 0), > fb->mem_path, errp); > g_free(path); > } > @@ -131,6 +133,26 @@ static void file_memory_backend_set_align(Object *o, Visitor *v, > error_propagate(errp, local_err); } > > +static bool file_memory_backend_get_pmem(Object *o, Error **errp) { > + return MEMORY_BACKEND_FILE(o)->is_pmem; } > + > +static void file_memory_backend_set_pmem(Object *o, bool value, Error > +**errp) { > + HostMemoryBackend *backend = MEMORY_BACKEND(o); > + HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o); > + > + if (host_memory_backend_mr_inited(backend)) { > + error_setg(errp, "cannot change property 'pmem' of %s '%s'", > + object_get_typename(o), > + object_get_canonical_path_component(o)); > + return; > + } > + > + fb->is_pmem = value; > +} > + > static void file_backend_unparent(Object *obj) { > HostMemoryBackend *backend = MEMORY_BACKEND(obj); @@ -162,6 > +184,9 @@ file_backend_class_init(ObjectClass *oc, void *data) > file_memory_backend_get_align, > file_memory_backend_set_align, > NULL, NULL, &error_abort); > + object_class_property_add_bool(oc, "pmem", > + file_memory_backend_get_pmem, file_memory_backend_set_pmem, > + &error_abort); > } > > static void file_backend_instance_finalize(Object *o) diff --git > a/docs/nvdimm.txt b/docs/nvdimm.txt index 8b48fb4..2f7d348 100644 > --- a/docs/nvdimm.txt > +++ b/docs/nvdimm.txt > @@ -180,3 +180,21 @@ supports CPU Cache Flush and Memory Controller Flush on Power Loss, etc. > > For a complete list of the flags available and for more detailed > descriptions, please consult the ACPI spec. > + > +guest software that this vNVDIMM device contains a region that cannot > +accept persistent writes. In result, for example, the guest Linux > +NVDIMM driver, marks such vNVDIMM device as read-only. > + > +If the vNVDIMM backend is on the host persistent memory that can be > +accessed in SNIA NVM Programming Model [1] (e.g., Intel NVDIMM), it's > +suggested to set the 'pmem' option of memory-backend-file to 'on'. > +When 'pmem=on' and QEMU is built with libpmem [2] support (configured > +with --enable-libpmem), QEMU will take necessary operations to > +guarantee the persistence of its own writes to the vNVDIMM backend > +(e.g., in vNVDIMM label emulation and live migration). > + > +References > +---------- > + > +[1] SNIA NVM Programming Model: > +https://www.snia.org/sites/default/files/technical_work/final/NVMProg > +rammingModel_v1.2.pdf > +[2] PMDK: http://pmem.io/pmdk/ > diff --git a/exec.c b/exec.c > index 8e079df..c42483e 100644 > --- a/exec.c > +++ b/exec.c > @@ -2077,6 +2077,9 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, > Error *local_err = NULL; > int64_t file_size; > > + /* Just support these ram flags by now. */ > + assert(ram_flags == 0 || (ram_flags & (RAM_SHARED | RAM_PMEM))); > + > if (xen_enabled()) { > error_setg(errp, "-mem-path not supported with Xen"); > return NULL; > @@ -4007,6 +4010,11 @@ err: > return ret; > } > > +bool ramblock_is_pmem(RAMBlock *rb) > +{ > + return rb->flags & RAM_PMEM; > +} > + > #endif > > void page_size_init(void) > @@ -4105,3 +4113,4 @@ void mtree_print_dispatch(fprintf_function mon, > void *f, } > > #endif > + > diff --git a/include/exec/memory.h b/include/exec/memory.h index > 3769c06..7dd43b0 100644 > --- a/include/exec/memory.h > +++ b/include/exec/memory.h > @@ -122,6 +122,9 @@ typedef struct IOMMUNotifier IOMMUNotifier; > /* RAM can be migrated */ > #define RAM_MIGRATABLE (1 << 4) > > +/* RAM is a persistent kind memory */ #define RAM_PMEM (1 << 5) > + > static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn, > IOMMUNotifierFlag flags, > hwaddr start, hwaddr end) @@ > -613,6 +616,7 @@ void memory_region_init_resizeable_ram(MemoryRegion *mr, > * (getpagesize()) will be used. > * @ram_flags: Memory region features: > * - RAM_SHARED: memory must be mmaped with the MAP_SHARED flag > + * - RAM_PMEM: the memory is persistent memory > * Other bits are ignored now. > * @path: the path in which to allocate the RAM. > * @errp: pointer to Error*, to store an error if it happens. > diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h index > 5545cf3..3c65643 100644 > --- a/include/exec/ram_addr.h > +++ b/include/exec/ram_addr.h > @@ -70,6 +70,8 @@ static inline unsigned long int ramblock_recv_bitmap_offset(void *host_addr, > return host_addr_offset >> TARGET_PAGE_BITS; } > > +bool ramblock_is_pmem(RAMBlock *rb); > + > long qemu_getrampagesize(void); > unsigned long last_ram_page(void); > > @@ -84,6 +86,7 @@ unsigned long last_ram_page(void); > * @ram_flags: specify the properties of the ram block, which can be one > * or bit-or of following values > * - RAM_SHARED: mmap the backing file or device with MAP_SHARED > + * - RAM_PMEM: the backend @mem_path or @fd is persistent memory > * Other bits are ignored. > * @mem_path or @fd: specify the backing file or device > * @errp: pointer to Error*, to store an error if it happens diff > --git a/qemu-options.hx b/qemu-options.hx index c0d3951..006ca44 > 100644 > --- a/qemu-options.hx > +++ b/qemu-options.hx > @@ -4045,6 +4045,13 @@ requires an alignment different than the > default one used by QEMU, eg the device DAX /dev/dax0.0 requires 2M > alignment rather than 4K. In such cases, users can specify the required alignment via this option. > > +The @option{pmem} option specifies whether the backing file specified > +by @option{mem-path} is on the persistent memory that can be accessed > +using the SNIA NVM programming model (e.g. Intel NVDIMM). > +If @option{pmem}, QEMU will take necessary operations to guarantee > +the persistence of its own writes to @option{mem-path} (e.g. in > +vNVDIMM label emulation and live migration). > + > @item -object > memory-backend-ram,id=@var{id},merge=@var{on|off},dump=@var{on|off},sh > are=@var{on|off},prealloc=@var{on|off},size=@var{size},host-nodes=@var > {host-nodes},policy=@var{default|preferred|bind|interleave} > > Creates a memory backend object, which can be used to back the guest RAM.
diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c index 34c68bb..6a861f0 100644 --- a/backends/hostmem-file.c +++ b/backends/hostmem-file.c @@ -34,6 +34,7 @@ struct HostMemoryBackendFile { bool discard_data; char *mem_path; uint64_t align; + bool is_pmem; }; static void @@ -59,7 +60,8 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) memory_region_init_ram_from_file(&backend->mr, OBJECT(backend), path, backend->size, fb->align, - backend->share ? RAM_SHARED : 0, + (backend->share ? RAM_SHARED : 0) | + (fb->is_pmem ? RAM_PMEM : 0), fb->mem_path, errp); g_free(path); } @@ -131,6 +133,26 @@ static void file_memory_backend_set_align(Object *o, Visitor *v, error_propagate(errp, local_err); } +static bool file_memory_backend_get_pmem(Object *o, Error **errp) +{ + return MEMORY_BACKEND_FILE(o)->is_pmem; +} + +static void file_memory_backend_set_pmem(Object *o, bool value, Error **errp) +{ + HostMemoryBackend *backend = MEMORY_BACKEND(o); + HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o); + + if (host_memory_backend_mr_inited(backend)) { + error_setg(errp, "cannot change property 'pmem' of %s '%s'", + object_get_typename(o), + object_get_canonical_path_component(o)); + return; + } + + fb->is_pmem = value; +} + static void file_backend_unparent(Object *obj) { HostMemoryBackend *backend = MEMORY_BACKEND(obj); @@ -162,6 +184,9 @@ file_backend_class_init(ObjectClass *oc, void *data) file_memory_backend_get_align, file_memory_backend_set_align, NULL, NULL, &error_abort); + object_class_property_add_bool(oc, "pmem", + file_memory_backend_get_pmem, file_memory_backend_set_pmem, + &error_abort); } static void file_backend_instance_finalize(Object *o) diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt index 8b48fb4..2f7d348 100644 --- a/docs/nvdimm.txt +++ b/docs/nvdimm.txt @@ -180,3 +180,21 @@ supports CPU Cache Flush and Memory Controller Flush on Power Loss, etc. For a complete list of the flags available and for more detailed descriptions, please consult the ACPI spec. + +guest software that this vNVDIMM device contains a region that cannot +accept persistent writes. In result, for example, the guest Linux +NVDIMM driver, marks such vNVDIMM device as read-only. + +If the vNVDIMM backend is on the host persistent memory that can be +accessed in SNIA NVM Programming Model [1] (e.g., Intel NVDIMM), it's +suggested to set the 'pmem' option of memory-backend-file to 'on'. When +'pmem=on' and QEMU is built with libpmem [2] support (configured with +--enable-libpmem), QEMU will take necessary operations to guarantee +the persistence of its own writes to the vNVDIMM backend (e.g., in +vNVDIMM label emulation and live migration). + +References +---------- + +[1] SNIA NVM Programming Model: https://www.snia.org/sites/default/files/technical_work/final/NVMProgrammingModel_v1.2.pdf +[2] PMDK: http://pmem.io/pmdk/ diff --git a/exec.c b/exec.c index 8e079df..c42483e 100644 --- a/exec.c +++ b/exec.c @@ -2077,6 +2077,9 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, Error *local_err = NULL; int64_t file_size; + /* Just support these ram flags by now. */ + assert(ram_flags == 0 || (ram_flags & (RAM_SHARED | RAM_PMEM))); + if (xen_enabled()) { error_setg(errp, "-mem-path not supported with Xen"); return NULL; @@ -4007,6 +4010,11 @@ err: return ret; } +bool ramblock_is_pmem(RAMBlock *rb) +{ + return rb->flags & RAM_PMEM; +} + #endif void page_size_init(void) @@ -4105,3 +4113,4 @@ void mtree_print_dispatch(fprintf_function mon, void *f, } #endif + diff --git a/include/exec/memory.h b/include/exec/memory.h index 3769c06..7dd43b0 100644 --- a/include/exec/memory.h +++ b/include/exec/memory.h @@ -122,6 +122,9 @@ typedef struct IOMMUNotifier IOMMUNotifier; /* RAM can be migrated */ #define RAM_MIGRATABLE (1 << 4) +/* RAM is a persistent kind memory */ +#define RAM_PMEM (1 << 5) + static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn, IOMMUNotifierFlag flags, hwaddr start, hwaddr end) @@ -613,6 +616,7 @@ void memory_region_init_resizeable_ram(MemoryRegion *mr, * (getpagesize()) will be used. * @ram_flags: Memory region features: * - RAM_SHARED: memory must be mmaped with the MAP_SHARED flag + * - RAM_PMEM: the memory is persistent memory * Other bits are ignored now. * @path: the path in which to allocate the RAM. * @errp: pointer to Error*, to store an error if it happens. diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h index 5545cf3..3c65643 100644 --- a/include/exec/ram_addr.h +++ b/include/exec/ram_addr.h @@ -70,6 +70,8 @@ static inline unsigned long int ramblock_recv_bitmap_offset(void *host_addr, return host_addr_offset >> TARGET_PAGE_BITS; } +bool ramblock_is_pmem(RAMBlock *rb); + long qemu_getrampagesize(void); unsigned long last_ram_page(void); @@ -84,6 +86,7 @@ unsigned long last_ram_page(void); * @ram_flags: specify the properties of the ram block, which can be one * or bit-or of following values * - RAM_SHARED: mmap the backing file or device with MAP_SHARED + * - RAM_PMEM: the backend @mem_path or @fd is persistent memory * Other bits are ignored. * @mem_path or @fd: specify the backing file or device * @errp: pointer to Error*, to store an error if it happens diff --git a/qemu-options.hx b/qemu-options.hx index c0d3951..006ca44 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -4045,6 +4045,13 @@ requires an alignment different than the default one used by QEMU, eg the device DAX /dev/dax0.0 requires 2M alignment rather than 4K. In such cases, users can specify the required alignment via this option. +The @option{pmem} option specifies whether the backing file specified +by @option{mem-path} is on the persistent memory that can be accessed +using the SNIA NVM programming model (e.g. Intel NVDIMM). +If @option{pmem}, QEMU will take necessary operations to +guarantee the persistence of its own writes to @option{mem-path} +(e.g. in vNVDIMM label emulation and live migration). + @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} Creates a memory backend object, which can be used to back the guest RAM.