From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoffer Dall <christoffer.dall@arm.com>
Subject: Re: [RFC PATCH v2 05/23] KVM: arm: Add arch vcpu uninit hook
Date: Tue, 20 Nov 2018 11:56:53 +0100
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To: Dave Martin <Dave.Martin@arm.com>
Cc: Okamoto Takayuki <tokamoto@jp.fujitsu.com>, Christoffer Dall <cdall@kernel.org>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, Marc Zyngier <marc.zyngier@arm.com>, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm.com>, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org
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On Thu, Nov 15, 2018 at 04:40:31PM +0000, Dave Martin wrote:
> On Fri, Nov 02, 2018 at 09:05:36AM +0100, Christoffer Dall wrote:
> > On Fri, Sep 28, 2018 at 02:39:09PM +0100, Dave Martin wrote:
> > > In preparation for adding support for SVE in guests on arm64, a
> > > hook is needed for freeing additional per-vcpu memory when a vcpu
> > > is freed.
> > 
> > Can this commit motivate why we can't do the work in kvm_arch_vcpu_free,
> > which we use for freeing other data structures?
> > 
> > (Presumably, uninit is needed when you need to do something at the very
> > last step after releasing the struct pid.
> 
> It wasn't to do with that.
> 
> Rather, the division of responsibility between the vcpu_uninit and
> vcpu_free paths is not very clear.
> 
> In the earlier version of the series, I think SVE state may have been
> allocated rather early and we may have needed to free it in the failure
> path of kvm_arch_vcpu_create() (which just calls kvm_vcpu_uninit()).
> (Alternatively, I may just have been wrong.)
> 
> Now, the vcpu must be fully created before the KVM_ARM_SVE_CONFIG ioctl
> on it (which is what allocates sve_state) can succeed anyway.
> 
> So the distinction between these two teardown phases is probably no
> longer important.
> 
> I'll see whether I can get rid of this hook and free the SVE state in
> kvm_arch_vcpu_free() instead.
> 
> Does that make sense?
> 

Yes, thanks.

    Christoffer