Re: [PATCH V4 04/19] machine: aux-ram-share option

[Markus Armbruster]

Steve Sistare <steven.sistare@oracle.com> writes:

> Allocate auxilliary guest RAM as an anonymous file that is shareable
> with an external process.  This option applies to memory allocated as
> a side effect of creating various devices. It does not apply to
> memory-backend-objects, whether explicitly specified on the command
> line, or implicitly created by the -m command line option.
>
> This option is intended to support new migration modes, in which the
> memory region can be transferred in place to a new QEMU process, by sending
> the memfd file descriptor to the process.  Memory contents are preserved,
> and if the mode also transfers device descriptors, then pages that are
> locked in memory for DMA remain locked.  This behavior is a pre-requisite
> for supporting vfio, vdpa, and iommufd devices with the new modes.
>
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>

[...]

> diff --git a/qemu-options.hx b/qemu-options.hx
> index dacc979..02b9118 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -38,6 +38,9 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
>      "                nvdimm=on|off controls NVDIMM support (default=off)\n"
>      "                memory-encryption=@var{} memory encryption object to 
> use (default=none)\n"
>      "                hmat=on|off controls ACPI HMAT support (default=off)\n"
> +#ifdef CONFIG_POSIX
> +    "                aux-ram-share=on|off allocate auxiliary guest RAM as 
> shared (default: off)\n"
> +#endif
>      "                memory-backend='backend-id' specifies explicitly 
> provided backend for main RAM (default=none)\n"
>      "                
> cxl-fmw.0.targets.0=firsttarget,cxl-fmw.0.targets.1=secondtarget,cxl-fmw.0.size=size[,cxl-fmw.0.interleave-granularity=granularity]\n",
>      QEMU_ARCH_ALL)
> @@ -101,6 +104,18 @@ SRST
>          Enables or disables ACPI Heterogeneous Memory Attribute Table
>          (HMAT) support. The default is off.
>  
> +#ifdef CONFIG_POSIX
> +    ``aux-ram-share=on|off``
> +        Allocate auxiliary guest RAM as an anonymous file that is
> +        shareable with an external process.  This option applies to
> +        memory allocated as a side effect of creating various devices.
> +        It does not apply to memory-backend-objects, whether explicitly
> +        specified on the command line, or implicitly created by the -m
> +        command line option.
> +
> +        Some migration modes require aux-ram-share=on.
> +#endif
> +

I get

    Warning, treated as error:
    .../qemu-options.hx:117:Definition list ends without a blank line; 
unexpected unindent.

Putting the blank line before #endif works for me.

>      ``memory-backend='id'``
>          An alternative to legacy ``-mem-path`` and ``mem-prealloc`` options.
>          Allows to use a memory backend as main RAM.

[...]