Currently, when using a true R/O NVDIMM (ROM memory backend) with a label
area, the VM can easily crash QEMU by trying to write to the label area,
because the ROM memory is mmap'ed without PROT_WRITE.
    [root@vm-0 ~]# ndctl disable-region region0
    disabled 1 region
    [root@vm-0 ~]# ndctl zero-labels nmem0
    -> QEMU segfaults
Let's remember whether we have a ROM memory backend and properly
reject the write request:
    [root@vm-0 ~]# ndctl disable-region region0
    disabled 1 region
    [root@vm-0 ~]# ndctl zero-labels nmem0
    zeroed 0 nmem
In comparison, on a system with a R/W NVDIMM:
    [root@vm-0 ~]# ndctl disable-region region0
    disabled 1 region
    [root@vm-0 ~]# ndctl zero-labels nmem0
    zeroed 1 nmem
For ACPI, just return "unsupported", like if no label exists. For spapr,
return "H_P2", similar to when no label area exists.
Could we rely on the "unarmed" property? Maybe, but it looks cleaner to
only disallow what certainly cannot work.
After all "unarmed=on" primarily means: cannot accept persistent writes. In
theory, there might be setups where devices with "unarmed=on" set could
be used to host non-persistent data (temporary files, system RAM, ...); for
example, in Linux, admins can overwrite the "readonly" setting and still
write to the device -- which will work as long as we're not using ROM.
Allowing writing label data in such configurations can make sense.
Message-ID: <20230906120503.359863-2-david@redhat.com>
Fixes: dbd730e85987 ("nvdimm: check -object memory-backend-file, readonly=on option")
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
		
	
			
		
			
				
	
	
		
			287 lines
		
	
	
		
			8.5 KiB
		
	
	
	
		
			C
		
	
	
	
	
	
			
		
		
	
	
			287 lines
		
	
	
		
			8.5 KiB
		
	
	
	
		
			C
		
	
	
	
	
	
/*
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 * Non-Volatile Dual In-line Memory Module Virtualization Implementation
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 *
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 * Copyright(C) 2015 Intel Corporation.
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 *
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 * Author:
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 *  Xiao Guangrong <guangrong.xiao@linux.intel.com>
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 *
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 * Currently, it only supports PMEM Virtualization.
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 *
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 * This library is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * This library is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with this library; if not, see <http://www.gnu.org/licenses/>
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 */
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#include "qemu/osdep.h"
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#include "qemu/module.h"
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#include "qemu/pmem.h"
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#include "qapi/error.h"
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#include "qapi/visitor.h"
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#include "hw/mem/nvdimm.h"
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#include "hw/qdev-properties.h"
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#include "hw/mem/memory-device.h"
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#include "sysemu/hostmem.h"
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static void nvdimm_get_label_size(Object *obj, Visitor *v, const char *name,
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                                  void *opaque, Error **errp)
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{
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    NVDIMMDevice *nvdimm = NVDIMM(obj);
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    uint64_t value = nvdimm->label_size;
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    visit_type_size(v, name, &value, errp);
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}
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static void nvdimm_set_label_size(Object *obj, Visitor *v, const char *name,
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                                  void *opaque, Error **errp)
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{
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    NVDIMMDevice *nvdimm = NVDIMM(obj);
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    uint64_t value;
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    if (nvdimm->nvdimm_mr) {
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        error_setg(errp, "cannot change property value");
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        return;
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    }
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    if (!visit_type_size(v, name, &value, errp)) {
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        return;
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    }
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    if (value < MIN_NAMESPACE_LABEL_SIZE) {
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        error_setg(errp, "Property '%s.%s' (0x%" PRIx64 ") is required"
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                   " at least 0x%lx", object_get_typename(obj), name, value,
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                   MIN_NAMESPACE_LABEL_SIZE);
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        return;
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    }
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    nvdimm->label_size = value;
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}
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static void nvdimm_get_uuid(Object *obj, Visitor *v, const char *name,
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                                  void *opaque, Error **errp)
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{
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    NVDIMMDevice *nvdimm = NVDIMM(obj);
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    char *value = NULL;
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    value = qemu_uuid_unparse_strdup(&nvdimm->uuid);
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    visit_type_str(v, name, &value, errp);
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    g_free(value);
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}
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static void nvdimm_set_uuid(Object *obj, Visitor *v, const char *name,
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                                  void *opaque, Error **errp)
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{
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    NVDIMMDevice *nvdimm = NVDIMM(obj);
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    char *value;
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    if (!visit_type_str(v, name, &value, errp)) {
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        return;
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    }
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    if (qemu_uuid_parse(value, &nvdimm->uuid) != 0) {
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        error_setg(errp, "Property '%s.%s' has invalid value",
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                   object_get_typename(obj), name);
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    }
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    g_free(value);
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}
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static void nvdimm_init(Object *obj)
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{
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    object_property_add(obj, NVDIMM_LABEL_SIZE_PROP, "int",
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                        nvdimm_get_label_size, nvdimm_set_label_size, NULL,
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                        NULL);
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    object_property_add(obj, NVDIMM_UUID_PROP, "QemuUUID", nvdimm_get_uuid,
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                        nvdimm_set_uuid, NULL, NULL);
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}
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static void nvdimm_finalize(Object *obj)
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{
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    NVDIMMDevice *nvdimm = NVDIMM(obj);
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    g_free(nvdimm->nvdimm_mr);
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}
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static void nvdimm_prepare_memory_region(NVDIMMDevice *nvdimm, Error **errp)
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{
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    PCDIMMDevice *dimm = PC_DIMM(nvdimm);
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    uint64_t align, pmem_size, size;
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    MemoryRegion *mr;
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    g_assert(!nvdimm->nvdimm_mr);
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    if (!dimm->hostmem) {
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        error_setg(errp, "'" PC_DIMM_MEMDEV_PROP "' property must be set");
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        return;
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    }
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    mr = host_memory_backend_get_memory(dimm->hostmem);
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    align = memory_region_get_alignment(mr);
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    size = memory_region_size(mr);
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    pmem_size = size - nvdimm->label_size;
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    nvdimm->label_data = memory_region_get_ram_ptr(mr) + pmem_size;
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    pmem_size = QEMU_ALIGN_DOWN(pmem_size, align);
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    if (size <= nvdimm->label_size || !pmem_size) {
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        HostMemoryBackend *hostmem = dimm->hostmem;
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        error_setg(errp, "the size of memdev %s (0x%" PRIx64 ") is too "
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                   "small to contain nvdimm label (0x%" PRIx64 ") and "
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                   "aligned PMEM (0x%" PRIx64 ")",
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                   object_get_canonical_path_component(OBJECT(hostmem)),
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                   memory_region_size(mr), nvdimm->label_size, align);
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        return;
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    }
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    if (!nvdimm->unarmed && memory_region_is_rom(mr)) {
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        HostMemoryBackend *hostmem = dimm->hostmem;
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        error_setg(errp, "'unarmed' property must be 'on' since memdev %s "
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                   "is read-only",
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                   object_get_canonical_path_component(OBJECT(hostmem)));
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        return;
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    }
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    if (memory_region_is_rom(mr)) {
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        nvdimm->readonly = true;
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    }
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    nvdimm->nvdimm_mr = g_new(MemoryRegion, 1);
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    memory_region_init_alias(nvdimm->nvdimm_mr, OBJECT(dimm),
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                             "nvdimm-memory", mr, 0, pmem_size);
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    memory_region_set_nonvolatile(nvdimm->nvdimm_mr, true);
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    nvdimm->nvdimm_mr->align = align;
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}
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static MemoryRegion *nvdimm_md_get_memory_region(MemoryDeviceState *md,
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                                                 Error **errp)
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{
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    NVDIMMDevice *nvdimm = NVDIMM(md);
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    Error *local_err = NULL;
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    if (!nvdimm->nvdimm_mr) {
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        nvdimm_prepare_memory_region(nvdimm, &local_err);
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        if (local_err) {
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            error_propagate(errp, local_err);
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            return NULL;
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        }
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    }
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    return nvdimm->nvdimm_mr;
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}
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static void nvdimm_realize(PCDIMMDevice *dimm, Error **errp)
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{
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    NVDIMMDevice *nvdimm = NVDIMM(dimm);
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    NVDIMMClass *ndc = NVDIMM_GET_CLASS(nvdimm);
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    if (!nvdimm->nvdimm_mr) {
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        nvdimm_prepare_memory_region(nvdimm, errp);
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    }
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    if (ndc->realize) {
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        ndc->realize(nvdimm, errp);
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    }
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}
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static void nvdimm_unrealize(PCDIMMDevice *dimm)
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{
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    NVDIMMDevice *nvdimm = NVDIMM(dimm);
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    NVDIMMClass *ndc = NVDIMM_GET_CLASS(nvdimm);
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    if (ndc->unrealize) {
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        ndc->unrealize(nvdimm);
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    }
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}
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/*
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 * the caller should check the input parameters before calling
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 * label read/write functions.
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 */
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static void nvdimm_validate_rw_label_data(NVDIMMDevice *nvdimm, uint64_t size,
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                                        uint64_t offset, bool is_write)
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{
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    assert((nvdimm->label_size >= size + offset) && (offset + size > offset));
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    assert(!is_write || !nvdimm->readonly);
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}
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static void nvdimm_read_label_data(NVDIMMDevice *nvdimm, void *buf,
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                                   uint64_t size, uint64_t offset)
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{
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    nvdimm_validate_rw_label_data(nvdimm, size, offset, false);
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    memcpy(buf, nvdimm->label_data + offset, size);
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}
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static void nvdimm_write_label_data(NVDIMMDevice *nvdimm, const void *buf,
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                                    uint64_t size, uint64_t offset)
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{
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    MemoryRegion *mr;
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    PCDIMMDevice *dimm = PC_DIMM(nvdimm);
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    bool is_pmem = object_property_get_bool(OBJECT(dimm->hostmem),
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                                            "pmem", NULL);
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    uint64_t backend_offset;
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    nvdimm_validate_rw_label_data(nvdimm, size, offset, true);
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    if (!is_pmem) {
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        memcpy(nvdimm->label_data + offset, buf, size);
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    } else {
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        pmem_memcpy_persist(nvdimm->label_data + offset, buf, size);
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    }
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    mr = host_memory_backend_get_memory(dimm->hostmem);
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    backend_offset = memory_region_size(mr) - nvdimm->label_size + offset;
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    memory_region_set_dirty(mr, backend_offset, size);
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}
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static Property nvdimm_properties[] = {
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    DEFINE_PROP_BOOL(NVDIMM_UNARMED_PROP, NVDIMMDevice, unarmed, false),
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    DEFINE_PROP_END_OF_LIST(),
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};
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static void nvdimm_class_init(ObjectClass *oc, void *data)
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{
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    PCDIMMDeviceClass *ddc = PC_DIMM_CLASS(oc);
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    MemoryDeviceClass *mdc = MEMORY_DEVICE_CLASS(oc);
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    NVDIMMClass *nvc = NVDIMM_CLASS(oc);
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    DeviceClass *dc = DEVICE_CLASS(oc);
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    ddc->realize = nvdimm_realize;
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    ddc->unrealize = nvdimm_unrealize;
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    mdc->get_memory_region = nvdimm_md_get_memory_region;
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    device_class_set_props(dc, nvdimm_properties);
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    nvc->read_label_data = nvdimm_read_label_data;
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    nvc->write_label_data = nvdimm_write_label_data;
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    set_bit(DEVICE_CATEGORY_STORAGE, dc->categories);
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}
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static const TypeInfo nvdimm_info = {
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    .name          = TYPE_NVDIMM,
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    .parent        = TYPE_PC_DIMM,
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    .class_size    = sizeof(NVDIMMClass),
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    .class_init    = nvdimm_class_init,
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    .instance_size = sizeof(NVDIMMDevice),
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    .instance_init = nvdimm_init,
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    .instance_finalize = nvdimm_finalize,
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};
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static void nvdimm_register_types(void)
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{
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    type_register_static(&nvdimm_info);
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}
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type_init(nvdimm_register_types)
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