linux-kernel - Re: [PATCH 1/7] KVM: x86: Free vCPUs before freeing VM state

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Message-ID: <Z75f9GuA9NfKo37c@google.com>
Date: Tue, 25 Feb 2025 16:27:32 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
	Tianrui Zhao <zhaotianrui@...ngson.cn>, Bibo Mao <maobibo@...ngson.cn>, 
	Huacai Chen <chenhuacai@...nel.org>, Madhavan Srinivasan <maddy@...ux.ibm.com>, 
	Anup Patel <anup@...infault.org>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Christian Borntraeger <borntraeger@...ux.ibm.com>, Janosch Frank <frankja@...ux.ibm.com>, 
	Claudio Imbrenda <imbrenda@...ux.ibm.com>, linux-arm-kernel@...ts.infradead.org, 
	kvmarm@...ts.linux.dev, kvm@...r.kernel.org, loongarch@...ts.linux.dev, 
	linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, 
	kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, Aaron Lewis <aaronlewis@...gle.com>, 
	Jim Mattson <jmattson@...gle.com>, Yan Zhao <yan.y.zhao@...el.com>, 
	Rick P Edgecombe <rick.p.edgecombe@...el.com>, Kai Huang <kai.huang@...el.com>, 
	Isaku Yamahata <isaku.yamahata@...el.com>
Subject: Re: [PATCH 1/7] KVM: x86: Free vCPUs before freeing VM state

On Wed, Feb 26, 2025, Paolo Bonzini wrote:
> On 2/25/25 00:55, Sean Christopherson wrote:
> > Free vCPUs before freeing any VM state, as both SVM and VMX may access
> > VM state when "freeing" a vCPU that is currently "in" L2, i.e. that needs
> > to be kicked out of nested guest mode.
> > 
> > Commit 6fcee03df6a1 ("KVM: x86: avoid loading a vCPU after .vm_destroy was
> > called") partially fixed the issue, but for unknown reasons only moved the
> > MMU unloading before VM destruction.  Complete the change, and free all
> > vCPU state prior to destroying VM state, as nVMX accesses even more state
> > than nSVM.
> 
> I applied this to kvm-coco-queue, I will place it in kvm/master too unless
> you shout.

Depends on what "this" is :-)

My plan/hope is to land patches 1 and 2 in 6.14, i.e. in kvm/master, but the
rest are firmly 6.15 IMO.  And based on Yan's feedback, I'm planning on adding a
few more cleanups (though I think they're fully additive, i.e. can go on top).