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Re: [PATCH v2 3/3] nvdimm: honor -object memory-backend-file, readonly=o
From: |
Igor Mammedov |
Subject: |
Re: [PATCH v2 3/3] nvdimm: honor -object memory-backend-file, readonly=on option |
Date: |
Mon, 14 Dec 2020 12:19:05 +0100 |
On Wed, 16 Sep 2020 10:51:50 +0100
Stefan Hajnoczi <stefanha@redhat.com> wrote:
> Make it possible to present read-only files to the guest as "unarmed"
> NVDIMMs. The Linux NVDIMM device (/dev/pmemX) is read-only.
>
> Acked-by: Michael S. Tsirkin <mst@redhat.com>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> docs/nvdimm.txt | 8 +++++++-
> hw/mem/nvdimm.c | 4 ++++
> 2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt
> index c2c6e441b3..06c2008107 100644
> --- a/docs/nvdimm.txt
> +++ b/docs/nvdimm.txt
> @@ -17,7 +17,7 @@ following command line options:
>
> -machine pc,nvdimm
> -m $RAM_SIZE,slots=$N,maxmem=$MAX_SIZE
> - -object
> memory-backend-file,id=mem1,share=on,mem-path=$PATH,size=$NVDIMM_SIZE
> + -object
> memory-backend-file,id=mem1,share=on,mem-path=$PATH,size=$NVDIMM_SIZE,readonly=off
> -device nvdimm,id=nvdimm1,memdev=mem1
>
> Where,
> @@ -42,6 +42,12 @@ Where,
> "share=off", then guest writes won't be applied to the backend
> file and thus will be invisible to other guests.
>
> + "readonly=on/off" controls whether the file $PATH is opened read-only or
> + read/write (default). "readonly=on" sets the ACPI NFIT NVDIMM Region
> Mapping
> + Structure "NVDIMM State Flags" Bit 3 indicating that the device is
> "unarmed"
> + and cannot accept persistent writes. Linux guest drivers set the device to
> + read-only when this bit is present.
> +
> - "device nvdimm,id=nvdimm1,memdev=mem1" creates a virtual NVDIMM
> device whose storage is provided by above memory backend device.
>
> diff --git a/hw/mem/nvdimm.c b/hw/mem/nvdimm.c
> index e1574bc07c..848cd65917 100644
> --- a/hw/mem/nvdimm.c
> +++ b/hw/mem/nvdimm.c
> @@ -146,6 +146,10 @@ static void nvdimm_prepare_memory_region(NVDIMMDevice
> *nvdimm, Error **errp)
> return;
> }
>
> + if (memory_region_is_rom(mr)) {
> + nvdimm->unarmed = true; /* this device is read-only */
> + }
we probably should error out in case 'backend,readonly=true +
nvdimm,unarmed=false'
instead of silently ignoring user's input
> nvdimm->nvdimm_mr = g_new(MemoryRegion, 1);
> memory_region_init_alias(nvdimm->nvdimm_mr, OBJECT(dimm),
> "nvdimm-memory", mr, 0, pmem_size);
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