diff options
| -rw-r--r-- | docs/nvdimm.txt | 15 | ||||
| -rw-r--r-- | hw/acpi/nvdimm.c | 7 | ||||
| -rw-r--r-- | hw/mem/nvdimm.c | 26 | ||||
| -rw-r--r-- | include/hw/mem/nvdimm.h | 9 |
4 files changed, 57 insertions, 0 deletions
diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt index 21249dd062..e903d8bb09 100644 --- a/docs/nvdimm.txt +++ b/docs/nvdimm.txt @@ -138,3 +138,18 @@ backend of vNVDIMM: -object memory-backend-file,id=mem1,share=on,mem-path=/dev/dax0.0,size=4G,align=2M -device nvdimm,id=nvdimm1,memdev=mem1 + +Guest Data Persistence +---------------------- + +Though QEMU supports multiple types of vNVDIMM backends on Linux, +currently the only one 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. + +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 +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. diff --git a/hw/acpi/nvdimm.c b/hw/acpi/nvdimm.c index 6ceea196e7..59d6e4254c 100644 --- a/hw/acpi/nvdimm.c +++ b/hw/acpi/nvdimm.c @@ -138,6 +138,8 @@ struct NvdimmNfitMemDev { } QEMU_PACKED; typedef struct NvdimmNfitMemDev NvdimmNfitMemDev; +#define ACPI_NFIT_MEM_NOT_ARMED (1 << 3) + /* * NVDIMM Control Region Structure * @@ -284,6 +286,7 @@ static void nvdimm_build_structure_memdev(GArray *structures, DeviceState *dev) { NvdimmNfitMemDev *nfit_memdev; + NVDIMMDevice *nvdimm = NVDIMM(OBJECT(dev)); uint64_t size = object_property_get_uint(OBJECT(dev), PC_DIMM_SIZE_PROP, NULL); int slot = object_property_get_int(OBJECT(dev), PC_DIMM_SLOT_PROP, @@ -312,6 +315,10 @@ nvdimm_build_structure_memdev(GArray *structures, DeviceState *dev) /* Only one interleave for PMEM. */ nfit_memdev->interleave_ways = cpu_to_le16(1); + + if (nvdimm->unarmed) { + nfit_memdev->flags |= cpu_to_le16(ACPI_NFIT_MEM_NOT_ARMED); + } } /* diff --git a/hw/mem/nvdimm.c b/hw/mem/nvdimm.c index 618c3d677b..61e677f92f 100644 --- a/hw/mem/nvdimm.c +++ b/hw/mem/nvdimm.c @@ -25,6 +25,7 @@ #include "qemu/osdep.h" #include "qapi/error.h" #include "qapi/visitor.h" +#include "qapi-visit.h" #include "hw/mem/nvdimm.h" static void nvdimm_get_label_size(Object *obj, Visitor *v, const char *name, @@ -64,11 +65,36 @@ out: error_propagate(errp, local_err); } +static bool nvdimm_get_unarmed(Object *obj, Error **errp) +{ + NVDIMMDevice *nvdimm = NVDIMM(obj); + + return nvdimm->unarmed; +} + +static void nvdimm_set_unarmed(Object *obj, bool value, Error **errp) +{ + NVDIMMDevice *nvdimm = NVDIMM(obj); + Error *local_err = NULL; + + if (memory_region_size(&nvdimm->nvdimm_mr)) { + error_setg(&local_err, "cannot change property value"); + goto out; + } + + nvdimm->unarmed = value; + + out: + error_propagate(errp, local_err); +} + static void nvdimm_init(Object *obj) { object_property_add(obj, NVDIMM_LABLE_SIZE_PROP, "int", nvdimm_get_label_size, nvdimm_set_label_size, NULL, NULL, NULL); + object_property_add_bool(obj, NVDIMM_UNARMED_PROP, + nvdimm_get_unarmed, nvdimm_set_unarmed, NULL); } static MemoryRegion *nvdimm_get_memory_region(PCDIMMDevice *dimm, Error **errp) diff --git a/include/hw/mem/nvdimm.h b/include/hw/mem/nvdimm.h index 28e68ddf59..7fd87c4e1c 100644 --- a/include/hw/mem/nvdimm.h +++ b/include/hw/mem/nvdimm.h @@ -49,6 +49,7 @@ TYPE_NVDIMM) #define NVDIMM_LABLE_SIZE_PROP "label-size" +#define NVDIMM_UNARMED_PROP "unarmed" struct NVDIMMDevice { /* private */ @@ -74,6 +75,14 @@ struct NVDIMMDevice { * guest via ACPI NFIT and _FIT method if NVDIMM hotplug is supported. */ MemoryRegion nvdimm_mr; + + /* + * The 'on' value results in the unarmed flag set in ACPI NFIT, + * which can be used to notify guest implicitly that the host + * backend (e.g., files on HDD, /dev/pmemX, etc.) cannot guarantee + * the guest write persistence. + */ + bool unarmed; }; typedef struct NVDIMMDevice NVDIMMDevice; |