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Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-
From: |
Laszlo Ersek |
Subject: |
Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory |
Date: |
Tue, 24 Nov 2015 14:36:37 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 |
On 11/24/15 13:05, Paolo Bonzini wrote:
>
>
> On 24/11/2015 04:10, Fam Zheng wrote:
>> What about all the hot-plug commands that changes the memory layout?
>
> If the guest is stopped, they shouldn't. device_add does not enable new
> BARs for example, the guest does that after it receives the ACPI event
> for PCI hotplug (or similarly an interrupt for SHPC or PCIe hotplug).
>
> Actually I like the idea of background dump, and a separate thread is an
> obvious way to do it since QEMU's memory API is mostly thread safe.
I'm not trying to reject this patch just because "I don't like it". I
perceive it as extremely risky, and I don't know enough to review it
with *full coverage*. If you're willing to review it, and Peter can
assume the responsibility of supporting it down the road, feel free to
go ahead.
> However, qmp_dump_guest_memory should only proceed if the VM is stopped
> and is not in incoming migration (RUN_STATE_INMIGRATE); as you prefer.
> If the VM is stopped, there is no whack-a-mole; the memory should not be
> touched after vm_stop returns. The only special case is incoming migration.
>
> Regarding thread-safety, the thread needs to take
> qemu_mutex_ram_list_lock or rcu_read_lock in order to get the list of
> RAM regions. Even better, build a list of MemoryRegions in advance
> (protecting them with memory_region_ref) in the iothread, and consult it
> during the dump. At the end you can use memory_region_unref to release
> them.
>
> Paolo
>
- Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory, (continued)
- Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory, Peter Xu, 2015/11/23
- Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory, Fam Zheng, 2015/11/23
- Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory, Laszlo Ersek, 2015/11/24
- Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory, Fam Zheng, 2015/11/24
- Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory, Eric Blake, 2015/11/24
- Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory, Fam Zheng, 2015/11/24
- Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory, Peter Xu, 2015/11/24
- Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory, Fam Zheng, 2015/11/24
- Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory, Markus Armbruster, 2015/11/25
- Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory, Paolo Bonzini, 2015/11/24
- Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory,
Laszlo Ersek <=
- Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory, Paolo Bonzini, 2015/11/24
- Re: [Qemu-devel] [PATCH REPOST 0/2] Add basic "detach" support for dump-guest-memory, Peter Xu, 2015/11/25