Commit a4de8552 authored by Junyan He's avatar Junyan He Committed by Michael S. Tsirkin
Browse files

hostmem-file: add the 'pmem' option 



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. If 'pmem' is set while lack of libpmem
support, a error is generated.

Signed-off-by: default avatarJunyan He <junyan.he@intel.com>
Signed-off-by: default avatarHaozhong Zhang <haozhong.zhang@intel.com>
Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: default avatarIgor Mammedov <imammedo@redhat.com>
Reviewed-by: default avatarRichard Henderson <richard.henderson@linaro.org>
Reviewed-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 17824406

backends/hostmem-file.c

+41 −2
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ 
#include "qemu/osdep.h"

#include "qapi/error.h"

#include "qemu-common.h"

#include "qemu/error-report.h"

#include "sysemu/hostmem.h"

#include "sysemu/sysemu.h"

#include "qom/object_interfaces.h"
@@ -31,9 +32,10 @@ typedef struct HostMemoryBackendFile HostMemoryBackendFile; 
struct HostMemoryBackendFile {

    HostMemoryBackend parent_obj;



    bool discard_data;

    char *mem_path;

    uint64_t align;

    bool discard_data;

    bool is_pmem;

};



static void
@@ -59,7 +61,8 @@ 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 +134,39 @@ 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;

    }



#ifndef CONFIG_LIBPMEM

    if (value) {

        Error *local_err = NULL;

        error_setg(&local_err,

                   "Lack of libpmem support while setting the 'pmem=on'"

                   " of %s '%s'. We can't ensure data persistence.",

                   object_get_typename(o),

                   object_get_canonical_path_component(o));

        error_propagate(errp, local_err);

        return;

    }

#endif



    fb->is_pmem = value;

}



static void file_backend_unparent(Object *obj)

{

    HostMemoryBackend *backend = MEMORY_BACKEND(obj);
@@ -162,6 +198,9 @@ 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)

docs/nvdimm.txt

+22 −0
Original line number Diff line number Diff line
@@ -173,3 +173,25 @@ There are currently two valid values for this option: 
             the NVDIMMs in the event of power loss.  This implies that the

             platform also supports flushing dirty data through the memory

             controller on power loss.



If the vNVDIMM backend is in 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' is '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).

If 'pmem' is 'on' while there is no libpmem support, qemu will exit and report

a "lack of libpmem support" message to ensure the persistence is available.

For example, if we want to ensure the persistence for some backend file,

use the QEMU command line:



    -object memory-backend-file,id=nv_mem,mem-path=/XXX/yyy,size=4G,pmem=on



References

----------



[1] NVM Programming Model (NPM)

	Version 1.2

    https://www.snia.org/sites/default/files/technical_work/final/NVMProgrammingModel_v1.2.pdf

[2] Persistent Memory Development Kit (PMDK), formerly known as NVML project, home page:

    http://pmem.io/pmdk/

exec.c

+8 −0
Original line number Diff line number Diff line
@@ -2245,6 +2245,9 @@ 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 & ~(RAM_SHARED | RAM_PMEM)) == 0);



    if (xen_enabled()) {

        error_setg(errp, "-mem-path not supported with Xen");

        return NULL;
@@ -4072,6 +4075,11 @@ err: 
    return ret;

}



bool ramblock_is_pmem(RAMBlock *rb)

{

    return rb->flags & RAM_PMEM;

}



#endif



void page_size_init(void)

include/exec/memory.h

+4 −0
Original line number Diff line number Diff line
@@ -123,6 +123,9 @@ 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,
@@ -654,6 +657,7 @@ 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.

include/exec/ram_addr.h

+3 −0
Original line number Diff line number Diff line
@@ -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);



/**
@@ -83,6 +85,7 @@ long qemu_getrampagesize(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