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X-CSE-ConnectionGUID: FN75dfaOTJeoky/0PB8k8Q== X-CSE-MsgGUID: iXAbLythT7CDxnm+AHx0UQ== X-IronPort-AV: E=McAfee;i="6800,10657,11874"; a="110053718" X-IronPort-AV: E=Sophos;i="6.25,222,1779174000"; d="scan'208";a="110053718" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by orvoesa101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Aug 2026 22:58:11 -0700 X-CSE-ConnectionGUID: cUW8aUaXR5u17W+d+k7SFQ== X-CSE-MsgGUID: D9N+GuVcQ1SFu1yh9D48qw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,222,1779174000"; d="scan'208";a="257921021" Received: from binbinwu-mobl.ccr.corp.intel.com (HELO [10.124.245.162]) ([10.124.245.162]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Aug 2026 22:57:57 -0700 Message-ID: <36baf0ec-0b7c-4ffd-9a1e-dfe9617e057d@linux.intel.com> Date: Fri, 14 Aug 2026 13:57:55 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 18/41] KVM: TDX: Make source page optional for KVM_TDX_INIT_MEM_REGION To: ackerleytng@google.com Cc: aik@amd.com, andrew.jones@linux.dev, 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 , tarunsahu@google.com, Vlastimil Babka , 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: <20260807-gmem-inplace-conversion-v10-0-2fc18ee6d3ba@google.com> <20260807-gmem-inplace-conversion-v10-18-2fc18ee6d3ba@google.com> Content-Language: en-US From: Binbin Wu In-Reply-To: <20260807-gmem-inplace-conversion-v10-18-2fc18ee6d3ba@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 155DA40005 X-Rspamd-Server: rspam07 X-Stat-Signature: 3wh7uicmug9hz8cryerjups3j5gf7k4p X-HE-Tag: 1786687092-138055 X-HE-Meta: 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 UVvGddan nsPsjXQ3qPv8vUykBtnXqy8L9nOT2ga/luWjfHH5yFsDT47vBHQx7aSFqM5fK3lJMjYg0DCBGrY/rVwvebrFafD+hL4x5QtsfeBsIcP3ycKzpP6hxpBjCMBnjiDW/RwMr1QTSu8GkojmckueeBpa3E5ekbGJRrGT2Vuy/nLAAnEAfysJrR3v3+am3aoHXXcjSxYKTanfCH2fOw9h9KDEw2KfOM3Bni2e6d2cEwHCKJKtV6ZEPtsCoQt0wxIkcMCThlzFUv3EFanieLKPpd1LgZwHB6WdJrp3YOSOieRBPCzM2zZxz02QMEZ6Kg3ATRc0d8wDO Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/8/2026 5:52 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. > > Allow "no source page" only when gmem_in_place_conversion is enabled, > because retroactively adding support for out-of-place conversion would mean > requiring a userspace update for a feature that's being deprecated. > > Also, KVM supporting "no source page" without in-place conversion would > effectively be an obscure zero-page optimization that relies on the page > being zeroed when it is allocated by guest_memfd. > > Rejecting "no source page" without in-place conversion scenario is valuable > for KVM developers since it helps newcomers understand what exactly is and > isn't possible. > > Signed-off-by: Sean Christopherson Nit: Is Sean's SoB intentional here? > Tested-by: Shivank Garg > Signed-off-by: Ackerley Tng Reviewed-by:Binbin Wu > --- > 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 b272c20586a74..7654a9f5fa128 100644 > --- a/arch/x86/kvm/vmx/tdx.c > +++ b/arch/x86/kvm/vmx/tdx.c > @@ -3189,7 +3189,7 @@ 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; > > @@ -3235,7 +3235,8 @@ 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) || > !PAGE_ALIGNED(region.gpa) || !region.nr_pages || > region.gpa + (region.nr_pages << PAGE_SHIFT) <= region.gpa || > !vt_is_tdx_private_gpa(kvm, region.gpa) || > @@ -3266,7 +3267,8 @@ 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--; > >