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Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resiz
From: |
Juan Quintela |
Subject: |
Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize |
Date: |
Wed, 19 Nov 2014 11:11:26 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.4 (gnu/linux) |
"Michael S. Tsirkin" <address@hidden> wrote:
> On Wed, Nov 19, 2014 at 10:19:22AM +0100, Juan Quintela wrote:
>> >> I very much prefer to have
>> >> user-controlled ACPI information (coming from the command-line)
>> >> byte-for-byte identical for a given machine type. Patches for that have
>> >> been on the list for almost two months, and it's not nice.
>> >>
>> >> Paolo
>> >
>> > I guess we just disagree on whether these patches will effectively achieve
>> > this goal. For example, some people want to rewrite iasl bits,
>> > generating everything in C. This will affect static bits too.
>> > I don't want to make every single change in code conditional
>> > on a machine type.
>>
>> You can't migrate with a different BIOS on destination, period.
>
> This claim is very wrong.
> This would make is impossible to change BIOS bus without breaking
> migration. Look at history of qemu, we change BIOS every release.
And we should do:
qemu -M pc-2.0 -L BIOS-2.0.bin
And that way for every version and every bios. If they are the same,
a symlink does. If they are not, different file. And we would not have
this problems.
I fully agree that we have problems with BIOS every relase. What we
don't agree is _what_ is the best way to fix the issue.
>> IMHO, b) is just asking for trouble. Being able to go from random
>> changes to random changes look strange.
>
> Yes, it is hard to support.
> But it's a required feature, and in fact, it's an existing one.
>> Just think about it for a second. We are sending more data for some
>> regions that it was allocated. And we just grow the regions and expect
>> that everything is going to be ok. It is me, or this goes against every
>> security discipline that I can think of?
>>
>> Later, Juan.
>
> We have many devices that just get N from stream, do malloc(N), then read
> data from stream into it.
> You think it's unsafe? Go ahead and fix them all.
I am sure it is unsafe. Fixing them requires incompatible changes, that
is the whole point :-(
> However, my patch does address your concern: callers specify the upper
> limit on the region size.
> Trying to migrate in a 1Gbyte region
Yes and no. You are assuming that a guest launched with a device ram
size of 256KB receives a 512KB section and it knows what to do with it.
It knows what to do with the 256KB section, with the 512KB answer is
always a "perhaps". It depends of what is on the extra space.
My solution would be that RAM/ROM sizes are always the same for
migration, so destination would always understand it.
It just forbids migrating between different machine types. And I think
that is good, not bad.
Later, Juan.
- [Qemu-devel] [PATCH 0/5] pc: make ROMs resizeable, Michael S. Tsirkin, 2014/11/17
- [Qemu-devel] [PATCH 1/5] cpu: add cpu_physical_memory_clear_dirty_range_nocode, Michael S. Tsirkin, 2014/11/17
- [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Michael S. Tsirkin, 2014/11/17
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Michael S. Tsirkin, 2014/11/17
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Paolo Bonzini, 2014/11/18
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Michael S. Tsirkin, 2014/11/18
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Juan Quintela, 2014/11/19
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Michael S. Tsirkin, 2014/11/19
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize,
Juan Quintela <=
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Michael S. Tsirkin, 2014/11/19
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Juan Quintela, 2014/11/19
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Michael S. Tsirkin, 2014/11/19
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Paolo Bonzini, 2014/11/19
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Juan Quintela, 2014/11/19
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Dr. David Alan Gilbert, 2014/11/19
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Paolo Bonzini, 2014/11/19
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Dr. David Alan Gilbert, 2014/11/19
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Paolo Bonzini, 2014/11/19
- Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize, Dr. David Alan Gilbert, 2014/11/19