linux-kernel - Re: [PATCH v19 044/130] KVM: TDX: Do TDX specific vcpu initialization

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Message-ID: <3f4f164a6375c8ada364dd2a83562a506019db86.camel@intel.com>
Date: Wed, 27 Mar 2024 00:27:03 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Yamahata,
 Isaku" <isaku.yamahata@...el.com>
CC: "Zhang, Tina" <tina.zhang@...el.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>, "Yuan, Hang" <hang.yuan@...el.com>, "Huang, Kai"
	<kai.huang@...el.com>, "Chen, Bo2" <chen.bo@...el.com>, "sagis@...gle.com"
	<sagis@...gle.com>, "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
	"Aktas, Erdem" <erdemaktas@...gle.com>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "sean.j.christopherson@...el.com"
	<sean.j.christopherson@...el.com>
Subject: Re: [PATCH v19 044/130] KVM: TDX: Do TDX specific vcpu initialization

On Mon, 2024-02-26 at 00:25 -0800, isaku.yamahata@...el.com wrote:
> +/* VMM can pass one 64bit auxiliary data to vcpu via RCX for guest BIOS. */
> +static int tdx_td_vcpu_init(struct kvm_vcpu *vcpu, u64 vcpu_rcx)
> +{
> +       struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm);
> +       struct vcpu_tdx *tdx = to_tdx(vcpu);
> +       unsigned long *tdvpx_pa = NULL;
> +       unsigned long tdvpr_pa;


I think we could drop theselocal variables and just use tdx->tdvpr_pa and tdx->tdvpx_pa. Then we
don't have to have the assignments later.

> +       unsigned long va;
> +       int ret, i;
> +       u64 err;
> +
> +       if (is_td_vcpu_created(tdx))
> +               return -EINVAL;
> +
> +       /*
> +        * vcpu_free method frees allocated pages.  Avoid partial setup so
> +        * that the method can't handle it.
> +        */
> +       va = __get_free_page(GFP_KERNEL_ACCOUNT);
> +       if (!va)
> +               return -ENOMEM;
> +       tdvpr_pa = __pa(va);
> +
> +       tdvpx_pa = kcalloc(tdx_info->nr_tdvpx_pages, sizeof(*tdx->tdvpx_pa),
> +                          GFP_KERNEL_ACCOUNT);
> +       if (!tdvpx_pa) {
> +               ret = -ENOMEM;
> +               goto free_tdvpr;
> +       }
> +       for (i = 0; i < tdx_info->nr_tdvpx_pages; i++) {
> +               va = __get_free_page(GFP_KERNEL_ACCOUNT);
> +               if (!va) {
> +                       ret = -ENOMEM;
> +                       goto free_tdvpx;
> +               }
> +               tdvpx_pa[i] = __pa(va);
> +       }
> +
> +       err = tdh_vp_create(kvm_tdx->tdr_pa, tdvpr_pa);
> +       if (KVM_BUG_ON(err, vcpu->kvm)) {
> +               ret = -EIO;
> +               pr_tdx_error(TDH_VP_CREATE, err, NULL);
> +               goto free_tdvpx;
> +       }
> +       tdx->tdvpr_pa = tdvpr_pa;
> +
> +       tdx->tdvpx_pa = tdvpx_pa;

Or alternatively let's move these to right before they are used. (in the current branch 

> +       for (i = 0; i < tdx_info->nr_tdvpx_pages; i++) {
> +               err = tdh_vp_addcx(tdx->tdvpr_pa, tdvpx_pa[i]);
> +               if (KVM_BUG_ON(err, vcpu->kvm)) {
> +                       pr_tdx_error(TDH_VP_ADDCX, err, NULL);
> +                       for (; i < tdx_info->nr_tdvpx_pages; i++) {
> +                               free_page((unsigned long)__va(tdvpx_pa[i]));
> +                               tdvpx_pa[i] = 0;
> +                       }
> +                       /* vcpu_free method frees TDVPX and TDR donated to TDX */
> +                       return -EIO;
> +               }
> +       }
> 
> 
In the current branch tdh_vp_init() takes struct vcpu_tdx, so they would be moved right here.

What do you think?

> +
> +       err = tdh_vp_init(tdx->tdvpr_pa, vcpu_rcx);
> +       if (KVM_BUG_ON(err, vcpu->kvm)) {
> +               pr_tdx_error(TDH_VP_INIT, err, NULL);
> +               return -EIO;
> +       }
> +
> +       vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
> +       tdx->td_vcpu_created = true;
> +       return 0;
> +
> +free_tdvpx:
> +       for (i = 0; i < tdx_info->nr_tdvpx_pages; i++) {
> +               if (tdvpx_pa[i])
> +                       free_page((unsigned long)__va(tdvpx_pa[i]));
> +               tdvpx_pa[i] = 0;
> +       }
> +       kfree(tdvpx_pa);
> +       tdx->tdvpx_pa = NULL;
> +free_tdvpr:
> +       if (tdvpr_pa)
> +               free_page((unsigned long)__va(tdvpr_pa));
> +       tdx->tdvpr_pa = 0;
> +
> +       return ret;
> +}