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Re: [Qemu-devel] [PATCH v4 1/3] hostmem-file: add "align" option
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH v4 1/3] hostmem-file: add "align" option |
Date: |
Wed, 13 Dec 2017 11:14:24 +0000 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Mon, Dec 11, 2017 at 03:28:04PM +0800, Haozhong Zhang wrote:
> 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 <address@hidden>
> ---
> backends/hostmem-file.c | 41 ++++++++++++++++++++++++++++++++++++++++-
> docs/nvdimm.txt | 16 ++++++++++++++++
> exec.c | 8 +++++++-
> include/exec/memory.h | 3 +++
> memory.c | 2 ++
> numa.c | 2 +-
> qemu-options.hx | 9 ++++++++-
> 7 files changed, 77 insertions(+), 4 deletions(-)
Reviewed-by: Stefan Hajnoczi <address@hidden>
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- [Qemu-devel] [PATCH for-2.12 v4 0/3] nvdimm: fixes for (non-)dax backends, Haozhong Zhang, 2017/12/11
- [Qemu-devel] [PATCH v4 2/3] nvdimm: add a macro for property "label-size", Haozhong Zhang, 2017/12/11
- [Qemu-devel] [PATCH v4 1/3] hostmem-file: add "align" option, Haozhong Zhang, 2017/12/11
- Re: [Qemu-devel] [PATCH v4 1/3] hostmem-file: add "align" option,
Stefan Hajnoczi <=
- [Qemu-devel] [PATCH v4 3/3] nvdimm: add 'unarmed' option, Haozhong Zhang, 2017/12/11
- Re: [Qemu-devel] [PATCH for-2.12 v4 0/3] nvdimm: fixes for (non-)dax backends, Stefan Hajnoczi, 2017/12/13
- Re: [Qemu-devel] [PATCH for-2.12 v4 0/3] nvdimm: fixes for (non-)dax backends, Michael S. Tsirkin, 2017/12/20