From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7DD732EE61B; Thu, 4 Sep 2025 09:17:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.7 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756977471; cv=none; b=Vb0vYk0/KkcXnBNuW5XYVBT/PDP/mAI7faUZdu5WAWbqB3EBsje843FIlGB5n2aRbRdFJoQSAVJukJB2UAszjXm8FD/sOHeIUZHu5TRXL56MzWItayKK8ccBbjJoe7BT9mura/mVkgj2+QCdHQFNGDbiPCHY8F0w+yczbQFf/H0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756977471; c=relaxed/simple; bh=AQpqNXGuwdtDJvMAxbZ3xMS7HgIncB27vU0YPQtZs+Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=JZEWmLMuG+bhbetXjAnxAofrF02umkpWAODc1UtHVCsBFMGWmz9y7i1X0e7xfa1YHOFOkwJuHzhf7shzKgxuhiw2oILuNy50Udtnc4RBTpm2liWlmxol819eRK5eahlAC9OX2woB3S08YJSLMWSMTohv3gBx6Xan1IIGh5X9v5E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=jJAWrYlU; arc=none smtp.client-ip=192.198.163.7 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="jJAWrYlU" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1756977469; x=1788513469; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=AQpqNXGuwdtDJvMAxbZ3xMS7HgIncB27vU0YPQtZs+Y=; b=jJAWrYlUcROxGMOEyX6AOQD+5Z6+bEtfanZ+QVV7b38WVwsINgRe8AuM Viu/7usp+I1Zwu0eJ608oMjcwH9n+0OwdAcnsJxgsWkl5jtT3Y2l3kRiO O1clQF53S4XSGx/yLRqjFDUVg/pj5Rj/W498NEDckxzhOXvtX86K4RIcm 2EQ1RZM9TP7VHfqLtfI5Kx01bJOfp10t4Rcvh7u2dPbuHmlrfKsyo2E/P OhBX7oe3GgyqdexABmhb97KJIUSjLbBHuao9tZ6+PUofiSCUqqbD1DunM Srqteef1y3rU70/iaGxXyulBVQcsg/zuxy9Z2oNlr5EOGR864pNAhmycR w==; X-CSE-ConnectionGUID: urXx3idNQvelscylAL/7zg== X-CSE-MsgGUID: iDijoNqLSIOZBrKvtGfu2A== X-IronPort-AV: E=McAfee;i="6800,10657,11542"; a="84739615" X-IronPort-AV: E=Sophos;i="6.18,237,1751266800"; d="scan'208";a="84739615" Received: from orviesa005.jf.intel.com ([10.64.159.145]) by fmvoesa101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Sep 2025 02:17:49 -0700 X-CSE-ConnectionGUID: HgCpv1rpQl2lZdm5XQX84w== X-CSE-MsgGUID: YQSugCF4Q0S0qKifcCsgZg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,237,1751266800"; d="scan'208";a="177101826" Received: from unknown (HELO [10.238.0.107]) ([10.238.0.107]) by orviesa005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Sep 2025 02:17:43 -0700 Message-ID: <1dccc546-65fc-4a73-9414-132299454985@linux.intel.com> Date: Thu, 4 Sep 2025 17:17:40 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v2 21/23] KVM: TDX: Preallocate PAMT pages to be used in split path To: Yan Zhao Cc: pbonzini@redhat.com, seanjc@google.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org, rick.p.edgecombe@intel.com, dave.hansen@intel.com, kas@kernel.org, tabba@google.com, ackerleytng@google.com, quic_eberman@quicinc.com, michael.roth@amd.com, david@redhat.com, vannapurve@google.com, vbabka@suse.cz, thomas.lendacky@amd.com, pgonda@google.com, zhiquan1.li@intel.com, fan.du@intel.com, jun.miao@intel.com, ira.weiny@intel.com, isaku.yamahata@intel.com, xiaoyao.li@intel.com, chao.p.peng@intel.com References: <20250807093950.4395-1-yan.y.zhao@intel.com> <20250807094604.4762-1-yan.y.zhao@intel.com> Content-Language: en-US From: Binbin Wu In-Reply-To: <20250807094604.4762-1-yan.y.zhao@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 8/7/2025 5:46 PM, Yan Zhao wrote: > From: "Kirill A. Shutemov" > > Preallocate a page to be used in the split_external_spt() path. Not just "a" page. > > Kernel needs one PAMT page pair for external_spt and one that provided > directly to the TDH.MEM.PAGE.DEMOTE SEAMCALL. > > Signed-off-by: Kirill A. Shutemov > Co-developed-by: Yan Zhao > Signed-off-by: Yan Zhao > --- > RFC v2: > - Pulled from > git://git.kernel.org/pub/scm/linux/kernel/git/kas/linux.git tdx/dpamt-huge. > - Implemented the flow of topup pamt_page_cache in > tdp_mmu_split_huge_pages_root() (Yan) > --- > arch/x86/include/asm/kvm_host.h | 2 ++ > arch/x86/kvm/mmu/mmu.c | 1 + > arch/x86/kvm/mmu/tdp_mmu.c | 51 +++++++++++++++++++++++++++++++++ > 3 files changed, 54 insertions(+) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 6b6c46c27390..508b133df903 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -1591,6 +1591,8 @@ struct kvm_arch { > #define SPLIT_DESC_CACHE_MIN_NR_OBJECTS (SPTE_ENT_PER_PAGE + 1) > struct kvm_mmu_memory_cache split_desc_cache; > > + struct kvm_mmu_memory_cache pamt_page_cache; > + > gfn_t gfn_direct_bits; > > /* > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index f23d8fc59323..e581cee37f64 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -6848,6 +6848,7 @@ static void mmu_free_vm_memory_caches(struct kvm *kvm) > kvm_mmu_free_memory_cache(&kvm->arch.split_desc_cache); > kvm_mmu_free_memory_cache(&kvm->arch.split_page_header_cache); > kvm_mmu_free_memory_cache(&kvm->arch.split_shadow_page_cache); > + kvm_mmu_free_memory_cache(&kvm->arch.pamt_page_cache); > } > > void kvm_mmu_uninit_vm(struct kvm *kvm) > diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c > index eb758aaa4374..064c4e823658 100644 > --- a/arch/x86/kvm/mmu/tdp_mmu.c > +++ b/arch/x86/kvm/mmu/tdp_mmu.c > @@ -1584,6 +1584,27 @@ static bool iter_cross_boundary(struct tdp_iter *iter, gfn_t start, gfn_t end) > (iter->gfn + KVM_PAGES_PER_HPAGE(iter->level)) <= end); > } > > +static bool need_topup_mirror_caches(struct kvm *kvm) > +{ > + int nr = tdx_nr_pamt_pages() * 2; > + > + return kvm_mmu_memory_cache_nr_free_objects(&kvm->arch.pamt_page_cache) < nr; > +} > + > +static int topup_mirror_caches(struct kvm *kvm) > +{ > + int r, nr; > + > + /* One for external_spt, one for TDH.MEM.PAGE.DEMOTE */ The comment is a bit confusing. IIUC, external_spt is also for TDH.MEM.PAGE.DEMOTE. and it's "one pair" for PAMT pages. > + nr = tdx_nr_pamt_pages() * 2; > + > + r = kvm_mmu_topup_memory_cache(&kvm->arch.pamt_page_cache, nr); > + if (r) > + return r; > + > + return 0; This could be simplified: diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 064c4e823658..35d052aa408c 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1593,16 +1593,12 @@ static bool need_topup_mirror_caches(struct kvm *kvm)  static int topup_mirror_caches(struct kvm *kvm)  { -       int r, nr; +       int nr;         /* One for external_spt, one for TDH.MEM.PAGE.DEMOTE */         nr = tdx_nr_pamt_pages() * 2; -       r = kvm_mmu_topup_memory_cache(&kvm->arch.pamt_page_cache, nr); -       if (r) -               return r; - -       return 0; +       return kvm_mmu_topup_memory_cache(&kvm->arch.pamt_page_cache, nr);  } > +} > + > static int tdp_mmu_split_huge_pages_root(struct kvm *kvm, > struct kvm_mmu_page *root, > gfn_t start, gfn_t end, > @@ -1656,6 +1677,36 @@ static int tdp_mmu_split_huge_pages_root(struct kvm *kvm, > continue; > } > > + if (is_mirror_sp(root) && need_topup_mirror_caches(kvm)) { > + int r; > + > + rcu_read_unlock(); > + > + if (shared) > + read_unlock(&kvm->mmu_lock); > + else > + write_unlock(&kvm->mmu_lock); > + > + r = topup_mirror_caches(kvm); > + > + if (shared) > + read_lock(&kvm->mmu_lock); > + else > + write_lock(&kvm->mmu_lock); > + > + if (r) { > + trace_kvm_mmu_split_huge_page(iter.gfn, > + iter.old_spte, > + iter.level, r); > + return r; > + } > + > + rcu_read_lock(); > + > + iter.yielded = true; > + continue; > + } > + > tdp_mmu_init_child_sp(sp, &iter); > > if (tdp_mmu_split_huge_page(kvm, &iter, sp, shared))