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Re: [PATCH 1/1] accel/kvm/kvm-all: fix vm crash when set dirty ring and
From: |
Peter Xu |
Subject: |
Re: [PATCH 1/1] accel/kvm/kvm-all: fix vm crash when set dirty ring and memorybacking |
Date: |
Thu, 23 Mar 2023 09:43:46 -0400 |
On Thu, Mar 23, 2023 at 09:19:15PM +0800, Jiajing Zhou wrote:
> From: "zhoujiajing.vergil" <zhoujiajing.vergil@bytedance.com>
>
> It is possible enter this function when the cpu not finished creating but
> is already in the cpu list. The value of dirty_gfns is null, causing vm
> crash here.
>
> When both dirty-ring and memorybacking are set, creating a vm will assert
> on kvm_dirty_ring_reap_one. Part of the xml as follows:
>
>
> <domain type='kvm' id='9'>
> ...
> <memoryBacking>
> <hugepages>
> <page size='2048' unit='KiB' memAccess='shared'/>
> </hugepages>
> </memoryBacking>
> ...
> <features>
> <acpi/>
> <kvm>
> <dirty-ring state='on' size='4096'/>
> </kvm>
> </features>
> ...
> <domain/>
>
> The kvm-reaper thread was created before vcpu thread, and the value of
> cpu->kvm_dirty_gfns is assigned at cpu thread. In the x86_cpu_realizefn
> function, the cpu is inserted into the cpu list first, and then the cpu
> thread is created for initialization. The entry functions are
> cpu_exec_realizefn and qemu_init_vcpu. In the existing logic, the
> kvm-reaper thread traverses the cpu list every second and finally call
> kvm_dirty_ring_reap_one for each cpu in the list. If cpu has been inserted
> into cpu list but has not been initialized so that the value of dirty_gfns
> is null, kvm-reaper thread call kvm_dirty_ring_reap_one will cause vm crash.
>
> The call stack is as follows:
> kvm_dirty_ring_reaper_thread
> -> kvm_dirty_ring_reap
> ->kvm_dirty_ring_reap_locked
> ->kvm_dirty_ring_reap_one
>
>
> Signed-off-by: zhoujiajing.vergil <zhoujiajing.vergil@bytedance.com>
Acked-by: Peter Xu <peterx@redhat.com>
And there's a prior fix last year:
https://lore.kernel.org/r/20220927154653.77296-1-peterx@redhat.com
The most recent post that I'm aware of is by Yong:
https://lore.kernel.org/r/1d14deb6684bcb7de1c9633c5bd21113988cc698.1676563222.git.huangy81@chinatelecom.cn
A bunch of people hit this already.
Paolo, ping yet again - would you consider merging any of the versions?
For this one I'd think it'll be good to have even for 8.0.
Thanks!
--
Peter Xu