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Re: [Qemu-devel] [PATCH v2 0/8] acpi: make ROMs resizeable
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH v2 0/8] acpi: make ROMs resizeable |
Date: |
Thu, 18 Dec 2014 21:43:18 +0200 |
On Thu, Dec 18, 2014 at 06:49:09PM +0000, Dr. David Alan Gilbert wrote:
> * Michael S. Tsirkin (address@hidden) wrote:
> > This is v2 of the patchset.
> > Changes since v1:
> > - Any RAM can now be resizeable - there's no requirement
> > that it's device RAM any longer.
> > - For simplicity, max_size RAM is always pre-allocated
> > - Added memory_region_set_size, to keep MR size consistent
> > in case MR is guest visible (even though for current users,
> > it never is)
> >
> > At the moment we migrate ROMs which reside in fw cfg, which allows
> > changing ROM code at will, and supports migrating largish blocks early,
> > with good performance.
> > However, we are running into a problem: changing size breaks
> > migration every time.
> > This already requires somewhat messy compatibility support in
> > acpi generation code, and it looks like there'll be more to come.
> >
> > In particular, recent patchsets by Igor et al. change table sizes in
> > unpredictable ways.
> >
> > Rather than try to guess the correct size once and for all,
> > this patchset tries to make code future-proof, by
> > adding support for resizeable ram blocks.
> >
> > A (possibly very high) amount of space in ram_addr_t space is reserved
> > and allocated in host for each block, but never used by fw cfg.
> > If incoming block size differs from current size, block is
> > reallocated. FW CFG is also notified and updated accordingly.
> >
> > As reviewers felt that making all RAM "resizeable" in this
> > way might make debugging migration harder, these patches
> > set a per-block flag and only allow resizing for blocks
> > where this was explicitly requested.
> >
> > Note: migration stream is unaffected by these patches.
> > This makes it possible to enable this functionality
> > unconditionally, for all machine types.
> >
> > In the future, this API might be handy for other things, besides ROMs.
>
> I'm generally happy with this set for what you're using it for,
> except that I'd like some big hairy warnings in comments
> near the resize functions to make it clear when it's safe
> to do it.
Really always: whenever resize callback updates all
guest visible state.
> What I don't really understand is how it would work for anything mapped
> into guest address space, how that mapping would be updated.
>
> Dave
That would be a job of the resize function: it can update kvm.
> >
> > Michael S. Tsirkin (8):
> > cpu: add cpu_physical_memory_clear_dirty_range_nocode
> > memory: add memory_region_set_size
> > exec: cpu_physical_memory_set/clear_dirty_range
> > exec: split length -> used_length/max_length
> > exec: qemu_ram_alloc_resizeable, qemu_ram_resize
> > arch_init: support resizing on incoming migration
> > memory: API to allocate resizeable RAM MR
> > acpi-build: make ROMs RAM blocks resizeable
> >
> > hw/lm32/lm32_hwsetup.h | 3 +-
> > include/exec/cpu-all.h | 12 +++--
> > include/exec/memory.h | 34 +++++++++++++
> > include/exec/ram_addr.h | 22 +++++++--
> > include/hw/loader.h | 4 +-
> > arch_init.c | 28 ++++++-----
> > exec.c | 129
> > +++++++++++++++++++++++++++++++++++++-----------
> > hw/core/loader.c | 18 +++++--
> > hw/i386/acpi-build.c | 19 +++++--
> > memory.c | 33 +++++++++++++
> > 10 files changed, 242 insertions(+), 60 deletions(-)
> >
> > --
> > MST
> >
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK
- [Qemu-devel] [PATCH v2 0/8] acpi: make ROMs resizeable, Michael S. Tsirkin, 2014/12/16
- [Qemu-devel] [PATCH v2 1/8] cpu: add cpu_physical_memory_clear_dirty_range_nocode, Michael S. Tsirkin, 2014/12/16
- [Qemu-devel] [PATCH v2 2/8] memory: add memory_region_set_size, Michael S. Tsirkin, 2014/12/16
- [Qemu-devel] [PATCH v2 3/8] exec: cpu_physical_memory_set/clear_dirty_range, Michael S. Tsirkin, 2014/12/16
- [Qemu-devel] [PATCH v2 4/8] exec: split length -> used_length/max_length, Michael S. Tsirkin, 2014/12/16
- [Qemu-devel] [PATCH v2 5/8] exec: qemu_ram_alloc_resizeable, qemu_ram_resize, Michael S. Tsirkin, 2014/12/16
- [Qemu-devel] [PATCH v2 6/8] arch_init: support resizing on incoming migration, Michael S. Tsirkin, 2014/12/16
- [Qemu-devel] [PATCH v2 7/8] memory: API to allocate resizeable RAM MR, Michael S. Tsirkin, 2014/12/16
- [Qemu-devel] [PATCH v2 8/8] acpi-build: make ROMs RAM blocks resizeable, Michael S. Tsirkin, 2014/12/16
- Re: [Qemu-devel] [PATCH v2 0/8] acpi: make ROMs resizeable, Dr. David Alan Gilbert, 2014/12/18
- Re: [Qemu-devel] [PATCH v2 0/8] acpi: make ROMs resizeable,
Michael S. Tsirkin <=