| Message ID | cb65ee91dd31df303dcb7c0e28143542678c9891.1542699775.git.yi.z.zhang@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | nvdimm: support MAP_SYNC for memory-backend-file | expand |
> > This option controls whether QEMU mmap(2) the memory backend file with > MAP_SYNC flag, which can fully guarantee the guest write persistence Not sure 'persistence' is the right word here. I think it should be something like 'consistent filesystem metadata for every guest write' just to avoid any confusion. > to the backend, if MAP_SYNC flag is supported by the host kernel > (Linux kernel 4.15 and later) and the backend is a file supporting > DAX (e.g., file on ext4/xfs file system mounted with '-o dax'). > > It can take one of following values: > - on: try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or > 'share=off', QEMU will abort > - off: never pass MAP_SYNC to mmap(2) > - auto (default): if MAP_SYNC is supported and 'share=on', work as if > 'sync=on'; otherwise, work as if 'sync=off' > > Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com> > Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com> > --- > backends/hostmem-file.c | 39 +++++++++++++++++++++++++++++++++++++++ > docs/nvdimm.txt | 20 +++++++++++++++++++- > include/exec/memory.h | 8 ++++++++ > qemu-options.hx | 22 +++++++++++++++++++++- > 4 files changed, 87 insertions(+), 2 deletions(-) > > diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c > index 0dd7a90..73cf181 100644 > --- a/backends/hostmem-file.c > +++ b/backends/hostmem-file.c > @@ -16,6 +16,7 @@ > #include "sysemu/hostmem.h" > #include "sysemu/sysemu.h" > #include "qom/object_interfaces.h" > +#include "qapi/qapi-visit.h" > > /* hostmem-file.c */ > /** > @@ -36,6 +37,7 @@ struct HostMemoryBackendFile { > uint64_t align; > bool discard_data; > bool is_pmem; > + OnOffAuto sync; > }; > > static void > @@ -62,6 +64,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error > **errp) > path, > backend->size, fb->align, > (backend->share ? RAM_SHARED : 0) | > + qemu_ram_sync_flags(fb->sync) | > (fb->is_pmem ? RAM_PMEM : 0), > fb->mem_path, errp); > g_free(path); > @@ -136,6 +139,39 @@ static void file_memory_backend_set_align(Object *o, > Visitor *v, > error_propagate(errp, local_err); > } > > +static void file_memory_backend_get_sync( > + Object *obj, Visitor *v, const char *name, void *opaque, Error **errp) > +{ > + HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj); > + OnOffAuto value = fb->sync; > + > + visit_type_OnOffAuto(v, name, &value, errp); > +} > + > +static void file_memory_backend_set_sync( > + Object *obj, Visitor *v, const char *name, void *opaque, Error **errp) > +{ > + HostMemoryBackend *backend = MEMORY_BACKEND(obj); > + HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj); > + Error *local_err = NULL; > + OnOffAuto value; > + > + if (host_memory_backend_mr_inited(backend)) { > + error_setg(&local_err, "cannot change property '%s' of %s", > + name, object_get_typename(obj)); > + goto out; > + } > + > + visit_type_OnOffAuto(v, name, &value, &local_err); > + if (local_err) { > + goto out; > + } > + fb->sync = value; > + > + out: > + error_propagate(errp, local_err); > +} > + > static bool file_memory_backend_get_pmem(Object *o, Error **errp) > { > return MEMORY_BACKEND_FILE(o)->is_pmem; > @@ -203,6 +239,9 @@ file_backend_class_init(ObjectClass *oc, void *data) > object_class_property_add_bool(oc, "pmem", > file_memory_backend_get_pmem, file_memory_backend_set_pmem, > &error_abort); > + object_class_property_add(oc, "sync", "OnOffAuto", > + file_memory_backend_get_sync, file_memory_backend_set_sync, > + NULL, NULL, &error_abort); > } > > static void file_backend_instance_finalize(Object *o) > diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt > index 5f158a6..3d89174 100644 > --- a/docs/nvdimm.txt > +++ b/docs/nvdimm.txt > @@ -142,11 +142,29 @@ backend of vNVDIMM: > Guest Data Persistence > ---------------------- > > +vNVDIMM is designed and implemented to guarantee the guest data > +persistence on the backends even on the host crash and power > +failures. However, there are still some requirements and limitations > +as explained below. > + > Though QEMU supports multiple types of vNVDIMM backends on Linux, > -currently the only one that can guarantee the guest write persistence > +if MAP_SYNC is not supported by the host kernel and the backends, > +the only backend that can guarantee the guest write persistence > is the device DAX on the real NVDIMM device (e.g., /dev/dax0.0), to > which all guest access do not involve any host-side kernel cache. > > +mmap(2) flag MAP_SYNC is added since Linux kernel 4.15. On such > +systems, QEMU can mmap(2) the backend with MAP_SYNC, which can I think its important to clear about the type of backend. i.e DAX file on real NVDIMM device backend. Thanks, Pankaj > +guarantee the guest write persistence to vNVDIMM. Besides the host > +kernel support, enabling MAP_SYNC in QEMU also requires: > + > + - the backend is a file supporting DAX, e.g., a file on an ext4 or > + xfs file system mounted with '-o dax', > + > + - 'sync' option of memory-backend-file is not 'off', and > + > + - 'share' option of memory-backend-file is 'on'. > + > When using other types of backends, it's suggested to set 'unarmed' > option of '-device nvdimm' to 'on', which sets the unarmed flag of the > guest NVDIMM region mapping structure. This unarmed flag indicates > diff --git a/include/exec/memory.h b/include/exec/memory.h > index c74c467..b398abb 100644 > --- a/include/exec/memory.h > +++ b/include/exec/memory.h > @@ -26,6 +26,7 @@ > #include "qom/object.h" > #include "qemu/rcu.h" > #include "hw/qdev-core.h" > +#include "qapi/error.h" > > #define RAM_ADDR_INVALID (~(ram_addr_t)0) > > @@ -136,6 +137,13 @@ typedef struct IOMMUNotifier IOMMUNotifier; > > #define RAM_SYNC (RAM_SYNC_ON_OFF_AUTO_ON | RAM_SYNC_ON_OFF_AUTO_AUTO) > > +static inline uint64_t qemu_ram_sync_flags(OnOffAuto v) > +{ > + return v == ON_OFF_AUTO_OFF ? RAM_SYNC_ON_OFF_AUTO_OFF : > + v == ON_OFF_AUTO_ON ? RAM_SYNC_ON_OFF_AUTO_ON : > + RAM_SYNC_ON_OFF_AUTO_AUTO; > +} > + > static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn, > IOMMUNotifierFlag flags, > hwaddr start, hwaddr end, > diff --git a/qemu-options.hx b/qemu-options.hx > index 08f8516..77e8810 100644 > --- a/qemu-options.hx > +++ b/qemu-options.hx > @@ -3928,7 +3928,7 @@ property must be set. These objects are placed in the > > @table @option > > -@item -object > memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off},discard-data=@var{on|off},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},align=@var{align} > +@item -object > memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off},discard-data=@var{on|off},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},align=@var{align},sync=@var{on|off|auto} > > Creates a memory file backend object, which can be used to back > the guest RAM with huge pages. > @@ -4003,6 +4003,26 @@ If @option{pmem} is set to 'on', 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). > > +The @option{sync} option specifies whether QEMU mmap(2) @option{mem-path} > +with MAP_SYNC flag, which can guarantee the guest write persistence to > +@option{mem-path} even on the host crash and power failures. MAP_SYNC > +requires supports from both the host kernel (since Linux kernel 4.15) > +and @option{mem-path} (only files supporting DAX). It can take one of > +following values: > + > +@table @option > +@item @var{on} > +try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or > +@option{share}=@var{off}, QEMU will abort > + > +@item @var{off} > +never pass MAP_SYNC to mmap(2) > + > +@item @var{auto} (default) > +if MAP_SYNC is supported and @option{share}=@var{on}, work as if > +@option{sync}=@var{on}; otherwise, work as if @option{sync}=@var{off} > +@end table > + > @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. > -- > 2.7.4 > > >
On 2018-11-26 at 03:46:50 -0500, Pankaj Gupta wrote: > > > > > This option controls whether QEMU mmap(2) the memory backend file with > > MAP_SYNC flag, which can fully guarantee the guest write persistence > > Not sure 'persistence' is the right word here. I think it should be > something like 'consistent filesystem metadata for every guest write' just > to avoid any confusion. Yes, Agree, the main porpurse of this flag is "*consistent filesystem metadata", I will improve that comments in next version Regards Yi. > > > to the backend, if MAP_SYNC flag is supported by the host kernel > > (Linux kernel 4.15 and later) and the backend is a file supporting > > DAX (e.g., file on ext4/xfs file system mounted with '-o dax'). > > > > It can take one of following values: > > - on: try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or > > 'share=off', QEMU will abort > > - off: never pass MAP_SYNC to mmap(2) > > - auto (default): if MAP_SYNC is supported and 'share=on', work as if > > 'sync=on'; otherwise, work as if 'sync=off' > > > > Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com> > > Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com> > > --- > > backends/hostmem-file.c | 39 +++++++++++++++++++++++++++++++++++++++ > > docs/nvdimm.txt | 20 +++++++++++++++++++- > > include/exec/memory.h | 8 ++++++++ > > qemu-options.hx | 22 +++++++++++++++++++++- > > 4 files changed, 87 insertions(+), 2 deletions(-) > > > > diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c > > index 0dd7a90..73cf181 100644 > > --- a/backends/hostmem-file.c > > +++ b/backends/hostmem-file.c > > @@ -16,6 +16,7 @@ > > #include "sysemu/hostmem.h" > > #include "sysemu/sysemu.h" > > #include "qom/object_interfaces.h" > > +#include "qapi/qapi-visit.h" > > > > /* hostmem-file.c */ > > /** > > @@ -36,6 +37,7 @@ struct HostMemoryBackendFile { > > uint64_t align; > > bool discard_data; > > bool is_pmem; > > + OnOffAuto sync; > > }; > > > > static void > > @@ -62,6 +64,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error > > **errp) > > path, > > backend->size, fb->align, > > (backend->share ? RAM_SHARED : 0) | > > + qemu_ram_sync_flags(fb->sync) | > > (fb->is_pmem ? RAM_PMEM : 0), > > fb->mem_path, errp); > > g_free(path); > > @@ -136,6 +139,39 @@ static void file_memory_backend_set_align(Object *o, > > Visitor *v, > > error_propagate(errp, local_err); > > } > > > > +static void file_memory_backend_get_sync( > > + Object *obj, Visitor *v, const char *name, void *opaque, Error **errp) > > +{ > > + HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj); > > + OnOffAuto value = fb->sync; > > + > > + visit_type_OnOffAuto(v, name, &value, errp); > > +} > > + > > +static void file_memory_backend_set_sync( > > + Object *obj, Visitor *v, const char *name, void *opaque, Error **errp) > > +{ > > + HostMemoryBackend *backend = MEMORY_BACKEND(obj); > > + HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj); > > + Error *local_err = NULL; > > + OnOffAuto value; > > + > > + if (host_memory_backend_mr_inited(backend)) { > > + error_setg(&local_err, "cannot change property '%s' of %s", > > + name, object_get_typename(obj)); > > + goto out; > > + } > > + > > + visit_type_OnOffAuto(v, name, &value, &local_err); > > + if (local_err) { > > + goto out; > > + } > > + fb->sync = value; > > + > > + out: > > + error_propagate(errp, local_err); > > +} > > + > > static bool file_memory_backend_get_pmem(Object *o, Error **errp) > > { > > return MEMORY_BACKEND_FILE(o)->is_pmem; > > @@ -203,6 +239,9 @@ file_backend_class_init(ObjectClass *oc, void *data) > > object_class_property_add_bool(oc, "pmem", > > file_memory_backend_get_pmem, file_memory_backend_set_pmem, > > &error_abort); > > + object_class_property_add(oc, "sync", "OnOffAuto", > > + file_memory_backend_get_sync, file_memory_backend_set_sync, > > + NULL, NULL, &error_abort); > > } > > > > static void file_backend_instance_finalize(Object *o) > > diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt > > index 5f158a6..3d89174 100644 > > --- a/docs/nvdimm.txt > > +++ b/docs/nvdimm.txt > > @@ -142,11 +142,29 @@ backend of vNVDIMM: > > Guest Data Persistence > > ---------------------- > > > > +vNVDIMM is designed and implemented to guarantee the guest data > > +persistence on the backends even on the host crash and power > > +failures. However, there are still some requirements and limitations > > +as explained below. > > + > > Though QEMU supports multiple types of vNVDIMM backends on Linux, > > -currently the only one that can guarantee the guest write persistence > > +if MAP_SYNC is not supported by the host kernel and the backends, > > +the only backend that can guarantee the guest write persistence > > is the device DAX on the real NVDIMM device (e.g., /dev/dax0.0), to > > which all guest access do not involve any host-side kernel cache. > > > > +mmap(2) flag MAP_SYNC is added since Linux kernel 4.15. On such > > +systems, QEMU can mmap(2) the backend with MAP_SYNC, which can > > I think its important to clear about the type of backend. > i.e DAX file on real NVDIMM device backend. > > Thanks, > Pankaj > > > +guarantee the guest write persistence to vNVDIMM. Besides the host > > +kernel support, enabling MAP_SYNC in QEMU also requires: > > + > > + - the backend is a file supporting DAX, e.g., a file on an ext4 or > > + xfs file system mounted with '-o dax', > > + > > + - 'sync' option of memory-backend-file is not 'off', and > > + > > + - 'share' option of memory-backend-file is 'on'. > > + > > When using other types of backends, it's suggested to set 'unarmed' > > option of '-device nvdimm' to 'on', which sets the unarmed flag of the > > guest NVDIMM region mapping structure. This unarmed flag indicates > > diff --git a/include/exec/memory.h b/include/exec/memory.h > > index c74c467..b398abb 100644 > > --- a/include/exec/memory.h > > +++ b/include/exec/memory.h > > @@ -26,6 +26,7 @@ > > #include "qom/object.h" > > #include "qemu/rcu.h" > > #include "hw/qdev-core.h" > > +#include "qapi/error.h" > > > > #define RAM_ADDR_INVALID (~(ram_addr_t)0) > > > > @@ -136,6 +137,13 @@ typedef struct IOMMUNotifier IOMMUNotifier; > > > > #define RAM_SYNC (RAM_SYNC_ON_OFF_AUTO_ON | RAM_SYNC_ON_OFF_AUTO_AUTO) > > > > +static inline uint64_t qemu_ram_sync_flags(OnOffAuto v) > > +{ > > + return v == ON_OFF_AUTO_OFF ? RAM_SYNC_ON_OFF_AUTO_OFF : > > + v == ON_OFF_AUTO_ON ? RAM_SYNC_ON_OFF_AUTO_ON : > > + RAM_SYNC_ON_OFF_AUTO_AUTO; > > +} > > + > > static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn, > > IOMMUNotifierFlag flags, > > hwaddr start, hwaddr end, > > diff --git a/qemu-options.hx b/qemu-options.hx > > index 08f8516..77e8810 100644 > > --- a/qemu-options.hx > > +++ b/qemu-options.hx > > @@ -3928,7 +3928,7 @@ property must be set. These objects are placed in the > > > > @table @option > > > > -@item -object > > memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off},discard-data=@var{on|off},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},align=@var{align} > > +@item -object > > memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off},discard-data=@var{on|off},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},align=@var{align},sync=@var{on|off|auto} > > > > Creates a memory file backend object, which can be used to back > > the guest RAM with huge pages. > > @@ -4003,6 +4003,26 @@ If @option{pmem} is set to 'on', 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). > > > > +The @option{sync} option specifies whether QEMU mmap(2) @option{mem-path} > > +with MAP_SYNC flag, which can guarantee the guest write persistence to > > +@option{mem-path} even on the host crash and power failures. MAP_SYNC > > +requires supports from both the host kernel (since Linux kernel 4.15) > > +and @option{mem-path} (only files supporting DAX). It can take one of > > +following values: > > + > > +@table @option > > +@item @var{on} > > +try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or > > +@option{share}=@var{off}, QEMU will abort > > + > > +@item @var{off} > > +never pass MAP_SYNC to mmap(2) > > + > > +@item @var{auto} (default) > > +if MAP_SYNC is supported and @option{share}=@var{on}, work as if > > +@option{sync}=@var{on}; otherwise, work as if @option{sync}=@var{off} > > +@end table > > + > > @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. > > -- > > 2.7.4 > > > > > >
diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c index 0dd7a90..73cf181 100644 --- a/backends/hostmem-file.c +++ b/backends/hostmem-file.c @@ -16,6 +16,7 @@ #include "sysemu/hostmem.h" #include "sysemu/sysemu.h" #include "qom/object_interfaces.h" +#include "qapi/qapi-visit.h" /* hostmem-file.c */ /** @@ -36,6 +37,7 @@ struct HostMemoryBackendFile { uint64_t align; bool discard_data; bool is_pmem; + OnOffAuto sync; }; static void @@ -62,6 +64,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) path, backend->size, fb->align, (backend->share ? RAM_SHARED : 0) | + qemu_ram_sync_flags(fb->sync) | (fb->is_pmem ? RAM_PMEM : 0), fb->mem_path, errp); g_free(path); @@ -136,6 +139,39 @@ static void file_memory_backend_set_align(Object *o, Visitor *v, error_propagate(errp, local_err); } +static void file_memory_backend_get_sync( + Object *obj, Visitor *v, const char *name, void *opaque, Error **errp) +{ + HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj); + OnOffAuto value = fb->sync; + + visit_type_OnOffAuto(v, name, &value, errp); +} + +static void file_memory_backend_set_sync( + Object *obj, Visitor *v, const char *name, void *opaque, Error **errp) +{ + HostMemoryBackend *backend = MEMORY_BACKEND(obj); + HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj); + Error *local_err = NULL; + OnOffAuto value; + + if (host_memory_backend_mr_inited(backend)) { + error_setg(&local_err, "cannot change property '%s' of %s", + name, object_get_typename(obj)); + goto out; + } + + visit_type_OnOffAuto(v, name, &value, &local_err); + if (local_err) { + goto out; + } + fb->sync = value; + + out: + error_propagate(errp, local_err); +} + static bool file_memory_backend_get_pmem(Object *o, Error **errp) { return MEMORY_BACKEND_FILE(o)->is_pmem; @@ -203,6 +239,9 @@ file_backend_class_init(ObjectClass *oc, void *data) object_class_property_add_bool(oc, "pmem", file_memory_backend_get_pmem, file_memory_backend_set_pmem, &error_abort); + object_class_property_add(oc, "sync", "OnOffAuto", + file_memory_backend_get_sync, file_memory_backend_set_sync, + NULL, NULL, &error_abort); } static void file_backend_instance_finalize(Object *o) diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt index 5f158a6..3d89174 100644 --- a/docs/nvdimm.txt +++ b/docs/nvdimm.txt @@ -142,11 +142,29 @@ backend of vNVDIMM: Guest Data Persistence ---------------------- +vNVDIMM is designed and implemented to guarantee the guest data +persistence on the backends even on the host crash and power +failures. However, there are still some requirements and limitations +as explained below. + Though QEMU supports multiple types of vNVDIMM backends on Linux, -currently the only one that can guarantee the guest write persistence +if MAP_SYNC is not supported by the host kernel and the backends, +the only backend that can guarantee the guest write persistence is the device DAX on the real NVDIMM device (e.g., /dev/dax0.0), to which all guest access do not involve any host-side kernel cache. +mmap(2) flag MAP_SYNC is added since Linux kernel 4.15. On such +systems, QEMU can mmap(2) the backend with MAP_SYNC, which can +guarantee the guest write persistence to vNVDIMM. Besides the host +kernel support, enabling MAP_SYNC in QEMU also requires: + + - the backend is a file supporting DAX, e.g., a file on an ext4 or + xfs file system mounted with '-o dax', + + - 'sync' option of memory-backend-file is not 'off', and + + - 'share' option of memory-backend-file is 'on'. + When using other types of backends, it's suggested to set 'unarmed' option of '-device nvdimm' to 'on', which sets the unarmed flag of the guest NVDIMM region mapping structure. This unarmed flag indicates diff --git a/include/exec/memory.h b/include/exec/memory.h index c74c467..b398abb 100644 --- a/include/exec/memory.h +++ b/include/exec/memory.h @@ -26,6 +26,7 @@ #include "qom/object.h" #include "qemu/rcu.h" #include "hw/qdev-core.h" +#include "qapi/error.h" #define RAM_ADDR_INVALID (~(ram_addr_t)0) @@ -136,6 +137,13 @@ typedef struct IOMMUNotifier IOMMUNotifier; #define RAM_SYNC (RAM_SYNC_ON_OFF_AUTO_ON | RAM_SYNC_ON_OFF_AUTO_AUTO) +static inline uint64_t qemu_ram_sync_flags(OnOffAuto v) +{ + return v == ON_OFF_AUTO_OFF ? RAM_SYNC_ON_OFF_AUTO_OFF : + v == ON_OFF_AUTO_ON ? RAM_SYNC_ON_OFF_AUTO_ON : + RAM_SYNC_ON_OFF_AUTO_AUTO; +} + static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn, IOMMUNotifierFlag flags, hwaddr start, hwaddr end, diff --git a/qemu-options.hx b/qemu-options.hx index 08f8516..77e8810 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -3928,7 +3928,7 @@ property must be set. These objects are placed in the @table @option -@item -object memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off},discard-data=@var{on|off},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},align=@var{align} +@item -object memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off},discard-data=@var{on|off},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},align=@var{align},sync=@var{on|off|auto} Creates a memory file backend object, which can be used to back the guest RAM with huge pages. @@ -4003,6 +4003,26 @@ If @option{pmem} is set to 'on', 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). +The @option{sync} option specifies whether QEMU mmap(2) @option{mem-path} +with MAP_SYNC flag, which can guarantee the guest write persistence to +@option{mem-path} even on the host crash and power failures. MAP_SYNC +requires supports from both the host kernel (since Linux kernel 4.15) +and @option{mem-path} (only files supporting DAX). It can take one of +following values: + +@table @option +@item @var{on} +try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or +@option{share}=@var{off}, QEMU will abort + +@item @var{off} +never pass MAP_SYNC to mmap(2) + +@item @var{auto} (default) +if MAP_SYNC is supported and @option{share}=@var{on}, work as if +@option{sync}=@var{on}; otherwise, work as if @option{sync}=@var{off} +@end table + @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.
This option controls whether QEMU mmap(2) the memory backend file with MAP_SYNC flag, which can fully guarantee the guest write persistence to the backend, if MAP_SYNC flag is supported by the host kernel (Linux kernel 4.15 and later) and the backend is a file supporting DAX (e.g., file on ext4/xfs file system mounted with '-o dax'). It can take one of following values: - on: try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or 'share=off', QEMU will abort - off: never pass MAP_SYNC to mmap(2) - auto (default): if MAP_SYNC is supported and 'share=on', work as if 'sync=on'; otherwise, work as if 'sync=off' Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com> Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com> --- backends/hostmem-file.c | 39 +++++++++++++++++++++++++++++++++++++++ docs/nvdimm.txt | 20 +++++++++++++++++++- include/exec/memory.h | 8 ++++++++ qemu-options.hx | 22 +++++++++++++++++++++- 4 files changed, 87 insertions(+), 2 deletions(-)