Re: [PATCH v6 00/79] refactor main RAM allocation to use hostmem backend

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Hi Igor,

On 2/19/20 5:08 PM, Igor Mammedov wrote:
[...]
> Series removes ad hoc RAM allocation API (memory_region_allocate_system_memory)
> and consolidates it around hostmem backend. It allows to
>   * resolve conflicts between global -mem-prealloc and hostmem's "policy" option
>     fixing premature allocation before binding policy is applied
>   * simplify complicated memory allocation routines which had to deal with 2 ways
>     to allocate RAM.
>   * it allows to reuse hostmem backends of a choice for main RAM without adding
>     extra CLI options to duplicate hostmem features.
>     Recent case was -mem-shared, to enable vhost-user on targets that don't
>     support hostmem backends [1] (ex: s390)
>   * move RAM allocation from individual boards into generic machine code and
>     provide them with prepared MemoryRegion.
>   * clean up deprecated NUMA features which were tied to the old API (see patches)
>      - "numa: remove deprecated -mem-path fallback to anonymous RAM"
>      - (POSTPONED, waiting on libvirt side) "forbid '-numa node,mem' for 5.0 and newer machine types"
>      - (POSTPONED) "numa: remove deprecated implicit RAM distribution between nodes"
> 
> Conversion introduces a new machine.memory-backend property and wrapper code that
> aliases global -mem-path and -mem-alloc into automatically created hostmem
> backend properties (provided memory-backend was not set explicitly given by user).
> And then follows bulk of trivial patches that incrementally convert individual
> boards to using machine.memory-backend provided MemoryRegion.
> 
> Board conversion typically involves:
>   * providing MachineClass::default_ram_size and MachineClass::default_ram_id
>     so generic code could create default backend if user didn't explicitly provide
>     memory-backend or -m options
>   * dropping memory_region_allocate_system_memory() call
>   * using convenience MachineState::ram MemoryRegion, which points to MemoryRegion
>     allocated by ram-memdev
> On top of that for some boards:
>   * added missing ram_size checks (typically it were boards with fixed ram size)
>   * ram_size fixups were replaced by checks and hard errors, forcing user to
>     provide correct "-m" values instead of ignoring it and continuing running.
> 
> After all boards are converted the old API is removed and memory allocation
> routines are cleaned up.

I wonder about the pre-QOM machines. As they don't call 
memory_region_allocate_system_memory(), the conversion is not required? 
(See for example pxa270_init).