linux-kernel - Re: [PATCH 0/4] KVM: Async #PF fixes and cleanups

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Message-ID: <170724643076.390683.15757663236296481465.b4-ty@google.com>
Date: Tue,  6 Feb 2024 13:36:13 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	David Matlack <dmatlack@...gle.com>, Xu Yilun <yilun.xu@...ux.intel.com>
Subject: Re: [PATCH 0/4] KVM: Async #PF fixes and cleanups

On Tue, 09 Jan 2024 17:15:29 -0800, Sean Christopherson wrote:
> Fix a use-after-module-unload bug in the async #PF code by ensuring all
> workqueue items fully complete before tearing down vCPUs.  Do a bit of
> cleanup to try and make the code slightly more readable.
> 
> Side topic, I'm pretty s390's flic_set_attr() is broken/racy.  The async #PF
> code assumes that only the vCPU can invoke
> kvm_clear_async_pf_completion_queue(), as there are multiple assets that
> are effectively protected by vcpu->mutex.  I don't any real world VMMs
> trigger the race(s), but AFAICT it's a bug.  I think/assume taking all
> vCPUs' mutexes would plug the hole?
> 
> [...]

Applied to kvm-x86 asyncpf, with comment tweaks as per Vitaly.  Thanks!

[1/4] KVM: Always flush async #PF workqueue when vCPU is being destroyed
      https://github.com/kvm-x86/linux/commit/3d75b8aa5c29
[2/4] KVM: Put mm immediately after async #PF worker completes remote gup()
      https://github.com/kvm-x86/linux/commit/422eeb543ac9
[3/4] KVM: Get reference to VM's address space in the async #PF worker
      https://github.com/kvm-x86/linux/commit/8284765f03b7
[4/4] KVM: Nullify async #PF worker's "apf" pointer as soon as it might be freed
      https://github.com/kvm-x86/linux/commit/c2744ed2230a

--
https://github.com/kvm-x86/linux/tree/next