linux-kernel - Re: [PATCH RESEND v4 5/9] KVM: VMX: Add init/set/get functions for SPP

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Date:   Tue, 20 Aug 2019 21:09:24 +0800
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Yang Weijiang <weijiang.yang@...el.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, sean.j.christopherson@...el.com,
        mst@...hat.com, rkrcmar@...hat.com, jmattson@...gle.com,
        yu.c.zhang@...el.com, alazar@...defender.com
Subject: Re: [PATCH RESEND v4 5/9] KVM: VMX: Add init/set/get functions for
 SPP

On Mon, Aug 19, 2019 at 05:13:47PM +0200, Paolo Bonzini wrote:
> On 14/08/19 09:03, Yang Weijiang wrote:
> >  static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
> >  	.cpu_has_kvm_support = cpu_has_kvm_support,
> >  	.disabled_by_bios = vmx_disabled_by_bios,
> > @@ -7740,6 +7783,11 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
> >  	.get_vmcs12_pages = NULL,
> >  	.nested_enable_evmcs = NULL,
> >  	.need_emulation_on_page_fault = vmx_need_emulation_on_page_fault,
> > +
> > +	.get_spp_status = vmx_get_spp_status,
> > +	.get_subpages = vmx_get_subpages,
> > +	.set_subpages = vmx_set_subpages,
> > +	.init_spp = vmx_init_spp,
> >  };
> 
> There's no need for the get_subpages kvm_x86_ops.  You do need init_spp
> of course, but you do not need get_spp_status either; instead you can
> check if init_spp is NULL (if NULL, SPP is not supported).
So first set .init_spp = NULL, then if all SPP preconditions meet, set
.init_spp = vmx_init_spp?

> In addition, kvm_mmu_set_subpages should not set up the SPP pages.  This
> should be handled entirely by handle_spp when the processor reports an
> SPPT miss, so you do not need that callback either.  You may need a
> flush_subpages callback, called by kvm_mmu_set_subpages to clear the SPP
> page tables for a given GPA range.  The next access then will cause an
> SPPT miss.
Good suggestion, thanks! Will do change.

> Finally, please move all SPP-related code to arch/x86/kvm/vmx/{spp.c,spp.h}.
>
Sure.

> Thanks,
> 
> Paolo
>