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X-CSE-ConnectionGUID: 3cKqbzgGR/+ZxCbDwQlZJA== X-CSE-MsgGUID: uIpEFN6uQoKqFPVg8HwgKQ== X-IronPort-AV: E=McAfee;i="6800,10657,11860"; a="86126083" X-IronPort-AV: E=Sophos;i="6.25,196,1779174000"; d="scan'208";a="86126083" Received: from fmviesa005.fm.intel.com ([10.60.135.145]) by orvoesa109.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Jul 2026 01:26:49 -0700 X-CSE-ConnectionGUID: KbSyPLdZQD6xu1UMvfTcHw== X-CSE-MsgGUID: g90yMGrGQQeZJeLvX6Oqmg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,196,1779174000"; d="scan'208";a="265591573" Received: from xiaoyaol-hp-g830.ccr.corp.intel.com (HELO [10.124.240.248]) ([10.124.240.248]) by fmviesa005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Jul 2026 01:26:34 -0700 Message-ID: Date: Fri, 31 Jul 2026 16:26:30 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 18/41] KVM: TDX: Make source page optional for KVM_TDX_INIT_MEM_REGION To: ackerleytng@google.com, aik@amd.com, andrew.jones@linux.dev, binbin.wu@linux.intel.com, brauner@kernel.org, chao.p.peng@linux.intel.com, david@kernel.org, jmattson@google.com, jthoughton@google.com, michael.roth@amd.com, oupton@kernel.org, pankaj.gupta@amd.com, qperret@google.com, rick.p.edgecombe@intel.com, rientjes@google.com, shivankg@amd.com, steven.price@arm.com, tabba@google.com, willy@infradead.org, wyihan@google.com, yan.y.zhao@intel.com, forkloop@google.com, pratyush@kernel.org, suzuki.poulose@arm.com, aneesh.kumar@kernel.org, liam@infradead.org, Paolo Bonzini , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , Shuah Khan , Vishal Annapurve , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Baoquan He , Jason Gunthorpe , John Hubbard , Peter Xu , Vlastimil Babka Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev References: <20260728-gmem-inplace-conversion-v9-0-35f9aec2aed2@google.com> <20260728-gmem-inplace-conversion-v9-18-35f9aec2aed2@google.com> Content-Language: en-US From: Xiaoyao Li In-Reply-To: <20260728-gmem-inplace-conversion-v9-18-35f9aec2aed2@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 89A9020007 X-Rspam-User: X-Stat-Signature: b8u4wuxedr3z6rkp98gzadftjr56ujgx X-HE-Tag: 1785486410-29813 X-HE-Meta: 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 OxIfLKAL mkdXcItXaOoTvzZcBm9WzNo17OaBImzr0vqnmascjXxzSPGdhLFmNxPocuhHZs1RNOBIu4uoxmRICsZibtjts0U4tDk3VlxDC/ERl6Ag5aU5oN5vc1BpLHNY8DPy0B84MWjy+LqaoSf5KLEwuElWB/x02n5cBQMIjhQNj1RN8FaiL7tBZ0X3VGA+Jbbm5F+GnS8Sb6i4CNnNPsx4ciF+jSJ88k4c3d35kNGVUJbCPhdVOO2vXpbk3yrTbUsmTfxzqVMJ/lWjbXiH3xFCl0O8adNur4FzpOPJVtmqsGltlXiSSKV7l2zv/mtn9u0vc+aK1u8nSR/lv1P0MNQZwYwW77ifcTw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/29/2026 8:35 AM, Ackerley Tng via B4 Relay wrote: > From: Ackerley Tng > > Update tdx_gmem_post_populate() to handle cases where userspace requests > "no source page". To handle "no source page", populate (perform > TDH.MEM.PAGE.ADD) using memory in-place at the target PFN. > > Signed-off-by: Sean Christopherson > Tested-by: Shivank Garg > Signed-off-by: Ackerley Tng > --- > Documentation/virt/kvm/x86/intel-tdx.rst | 4 ++++ > arch/x86/kvm/vmx/tdx.c | 8 +++++--- > 2 files changed, 9 insertions(+), 3 deletions(-) > > diff --git a/Documentation/virt/kvm/x86/intel-tdx.rst b/Documentation/virt/kvm/x86/intel-tdx.rst > index 6a222e9d09541..d8d9409120e61 100644 > --- a/Documentation/virt/kvm/x86/intel-tdx.rst > +++ b/Documentation/virt/kvm/x86/intel-tdx.rst > @@ -158,6 +158,10 @@ KVM_TDX_INIT_MEM_REGION > Initialize @nr_pages TDX guest private memory starting from @gpa with userspace > provided data from @source_addr. @source_addr must be PAGE_SIZE-aligned. > > +If guest_memfd in-place conversion is enabled, pass 0 for @source_addr > +to represent "no source page". A source page is required if in-place > +conversion is not enabled or not supported. > + > Note, before calling this sub command, memory attribute of the range > [gpa, gpa + nr_pages] needs to be private. Userspace can use > KVM_SET_MEMORY_ATTRIBUTES to set the attribute. > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c > index d1af0a752e97e..e890da5f18aed 100644 > --- a/arch/x86/kvm/vmx/tdx.c > +++ b/arch/x86/kvm/vmx/tdx.c > @@ -3192,7 +3192,7 @@ static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, > if (KVM_BUG_ON(kvm_tdx->page_add_src, kvm)) > return -EIO; > > - kvm_tdx->page_add_src = src_page; > + kvm_tdx->page_add_src = src_page ?: pfn_to_page(pfn); > ret = kvm_tdp_mmu_map_private_pfn(arg->vcpu, gfn, pfn); > kvm_tdx->page_add_src = NULL; > > @@ -3238,7 +3238,8 @@ static int tdx_vcpu_init_mem_region(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *c > if (copy_from_user(®ion, u64_to_user_ptr(cmd->data), sizeof(region))) > return -EFAULT; > > - if (!PAGE_ALIGNED(region.source_addr) || !region.source_addr || > + if (!PAGE_ALIGNED(region.source_addr) || > + (!gmem_in_place_conversion && !region.source_addr) || Sorry, I still want to discuss why we only allow in-place PAGE.ADD for gmem_in_place_conversion only. Though Yan raised this opinion[1] in previous v8, I'm not quite following her argument. So let me try again. I think in-place PAGE.ADD of TDX doesn't need to depend on gmem_in_place_conversion. There are two use cases actually. 1). Userspace sets the gmem page as private, and invokes the in-place PAGE.ADD by passing a 0 source_addr. Due to patch 16, the target PFN will be ADD'ed to TD as a all-0 page. 2). Userspace sets the gmem page as shared, and writes the desired content to it. Then converts the page to private, and invokes the in-place PAGE.ADD by passing a 0 source_addr. The target PFN will be ADD'ed to TD with desired content. For gmem_in_place_conversion == false, only case 1) is possible. For gmem_in_place_conversion == true, both case 1) and 2) are possible. Basically, this patch is changing the behavior of KVM_TDX_INIT_MEM_REGION. Before, it returns -EINVAL when region.source_addr == 0. Now it wants to allow the "region.source_addr == 0" case. If we can allow it unconditionally, why bother adding the restriction to allow it only when gmem_in_place_conversion == true? [1] https://lore.kernel.org/all/akI9m02jgKAdi4gX@yzhao56-desk.sh.intel.com/ > !PAGE_ALIGNED(region.gpa) || !region.nr_pages || > region.gpa + (region.nr_pages << PAGE_SHIFT) <= region.gpa || > !vt_is_tdx_private_gpa(kvm, region.gpa) || > @@ -3269,7 +3270,8 @@ static int tdx_vcpu_init_mem_region(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *c > break; > } > > - region.source_addr += PAGE_SIZE; > + if (region.source_addr) > + region.source_addr += PAGE_SIZE; > region.gpa += PAGE_SIZE; > region.nr_pages--; > >