linux-kernel - Re: [PATCHv2 08/12] KVM: TDX: Handle PAMT allocation in fault path

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Message-ID: <aErF7JXwjmsf5zYp@intel.com>
Date: Thu, 12 Jun 2025 20:19:56 +0800
From: Chao Gao <chao.gao@...el.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
CC: <pbonzini@...hat.com>, <seanjc@...gle.com>, <dave.hansen@...ux.intel.com>,
	<rick.p.edgecombe@...el.com>, <isaku.yamahata@...el.com>,
	<kai.huang@...el.com>, <yan.y.zhao@...el.com>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <kvm@...r.kernel.org>, <x86@...nel.org>,
	<linux-coco@...ts.linux.dev>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2 08/12] KVM: TDX: Handle PAMT allocation in fault path

> int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn,
> 			      enum pg_level level, kvm_pfn_t pfn)
> {
>+	struct kvm_vcpu *vcpu = kvm_get_running_vcpu();
> 	struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
> 	struct page *page = pfn_to_page(pfn);
>+	int ret;
>+
>+	ret = tdx_pamt_get(page, level, tdx_alloc_pamt_page_atomic, vcpu);
>+	if (ret)
>+		return ret;
> 
> 	/* TODO: handle large pages. */
> 	if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm))

nit: hoist this before the tdx_pamt_get() above. otherwise, tdx_pamt_put()
should be called in this error path.

>@@ -1562,10 +1577,16 @@ int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn,
> 	 * barrier in tdx_td_finalize().
> 	 */
> 	smp_rmb();
>-	if (likely(kvm_tdx->state == TD_STATE_RUNNABLE))
>-		return tdx_mem_page_aug(kvm, gfn, level, page);
> 
>-	return tdx_mem_page_record_premap_cnt(kvm, gfn, level, pfn);
>+	if (likely(kvm_tdx->state == TD_STATE_RUNNABLE))
>+		ret = tdx_mem_page_aug(kvm, gfn, level, page);
>+	else
>+		ret = tdx_mem_page_record_premap_cnt(kvm, gfn, level, pfn);
>+
>+	if (ret)
>+		tdx_pamt_put(page, level);
>+
>+	return ret;
> }

<snip>