On Mon, 24 Feb 2020 09:45:11 +0100
Philippe Mathieu-Daudé <address@hidden> wrote:
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).
Since they weren't using memory_region_allocate_system_memory(), they are
out of scope of this series.
As for the future, I'd only make boards that support user configurable
ram size to accept "-m".
For fixed size boards -m/memdev is overkill and we need to decide what to do
with them. I see following options (in order of my preference):
1. Non popular: error out if -m is specified (it used to work, but not
anymore when check is added, i.e similar to size checks
introduced in this series so users have to adapt their CLI).
It can still use automatically created memdev but I'd ditch it on
those boards and use plain memory_region_init_ram().
This is matches well SoCs that have embedded RAM and don't really
care about what user may specify with -m. It would simplify
simple boards.