diff options
| author | Haozhong Zhang <haozhong.zhang@intel.com> | 2017-12-11 15:28:04 +0800 |
|---|---|---|
| committer | Eduardo Habkost <ehabkost@redhat.com> | 2018-01-19 11:18:51 -0200 |
| commit | 983768431676f9ab8599a0b4813e1ca17af70838 (patch) | |
| tree | 4923d3621cf664db0fe10092321df708f718c84f /qemu-options.hx | |
| parent | 1e2bdd2e20844f6bc343232ea1bb6f64c54a95ce (diff) | |
hostmem-file: add "align" option
When mmap(2) the backend files, QEMU uses the host page size
(getpagesize(2)) by default as the alignment of mapping address.
However, some backends may require alignments different than the page
size. For example, mmap a device DAX (e.g., /dev/dax0.0) on Linux
kernel 4.13 to an address, which is 4K-aligned but not 2M-aligned,
fails with a kernel message like
[617494.969768] dax dax0.0: qemu-system-x86: dax_mmap: fail, unaligned vma (0x7fa37c579000 - 0x7fa43c579000, 0x1fffff)
Because there is no common approach to get such alignment requirement,
we add the 'align' option to 'memory-backend-file', so that users or
management utils, which have enough knowledge about the backend, can
specify a proper alignment via this option.
Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Message-Id: <20171211072806.2812-2-haozhong.zhang@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
[ehabkost: fixed typo, fixed error_setg() format string]
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Diffstat (limited to 'qemu-options.hx')
| -rw-r--r-- | qemu-options.hx | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/qemu-options.hx b/qemu-options.hx index b3e03c5464..5ff741a4af 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -3974,7 +3974,7 @@ 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} +@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} Creates a memory file backend object, which can be used to back the guest RAM with huge pages. @@ -4027,6 +4027,13 @@ restrict memory allocation to the given host node list interleave memory allocations across the given host node list @end table +The @option{align} option specifies the base address alignment when +QEMU mmap(2) @option{mem-path}, and accepts common suffixes, eg +@option{2M}. Some backend store specified by @option{mem-path} +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. + @item -object memory-backend-ram,id=@var{id},merge=@var{on|off},dump=@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. |