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X-CSE-ConnectionGUID: gYVxCM5FTSmomkIvHTnTwA== X-CSE-MsgGUID: F5L1qljrS+yp8Aqjp6e5sA== X-IronPort-AV: E=McAfee;i="6800,10657,11663"; a="80555520" X-IronPort-AV: E=Sophos;i="6.21,206,1763452800"; d="scan'208";a="80555520" Received: from fmviesa001.fm.intel.com ([10.60.135.141]) by orvoesa104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Jan 2026 13:08:01 -0800 X-CSE-ConnectionGUID: oG0dtpXcSnCNzDRCcRXRXw== X-CSE-MsgGUID: 8iMOsDQJTU2eRiToMQXw8Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,206,1763452800"; d="scan'208";a="233889165" Received: from unknown (HELO [10.24.81.162]) ([10.24.81.162]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Jan 2026 13:08:00 -0800 Message-ID: Date: Tue, 6 Jan 2026 13:08:00 -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: [PATCH v3 01/24] x86/tdx: Enhance tdh_mem_page_aug() to support huge pages To: Yan Zhao , pbonzini@redhat.com, seanjc@google.com Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org, rick.p.edgecombe@intel.com, kas@kernel.org, tabba@google.com, ackerleytng@google.com, michael.roth@amd.com, david@kernel.org, vannapurve@google.com, sagis@google.com, vbabka@suse.cz, thomas.lendacky@amd.com, nik.borisov@suse.com, pgonda@google.com, fan.du@intel.com, jun.miao@intel.com, francescolavra.fl@gmail.com, jgross@suse.com, ira.weiny@intel.com, isaku.yamahata@intel.com, xiaoyao.li@intel.com, kai.huang@intel.com, binbin.wu@linux.intel.com, chao.p.peng@intel.com, chao.gao@intel.com References: <20260106101646.24809-1-yan.y.zhao@intel.com> <20260106101826.24870-1-yan.y.zhao@intel.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/6/26 02:18, Yan Zhao wrote: > Enhance the SEAMCALL wrapper tdh_mem_page_aug() to support huge pages. > > The SEAMCALL TDH_MEM_PAGE_AUG currently supports adding physical memory to > the S-EPT up to 2MB in size. > > While keeping the "level" parameter in the tdh_mem_page_aug() wrapper to > allow callers to specify the physical memory size, introduce the parameters > "folio" and "start_idx" to specify the physical memory starting from the > page at "start_idx" within the "folio". The specified physical memory must > be fully contained within a single folio. > > Invoke tdx_clflush_page() for each 4KB segment of the physical memory being > added. tdx_clflush_page() performs CLFLUSH operations conservatively to > prevent dirty cache lines from writing back later and corrupting TD memory. This changelog is heavy on the "what" and weak on the "why". It's not telling me what I need to know. ... > + struct folio *folio = page_folio(page); > gpa_t gpa = gfn_to_gpa(gfn); > u64 entry, level_state; > u64 err; > > - err = tdh_mem_page_aug(&kvm_tdx->td, gpa, tdx_level, page, &entry, &level_state); > - > + err = tdh_mem_page_aug(&kvm_tdx->td, gpa, tdx_level, folio, > + folio_page_idx(folio, page), &entry, &level_state); > if (unlikely(IS_TDX_OPERAND_BUSY(err))) > return -EBUSY; For example, 'folio' is able to be trivially derived from page. Yet, this removes the 'page' argument and replaces it with 'folio' _and_ another value which can be derived from 'page'. This looks superficially like an illogical change. *Why* was this done? > diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c > index b0b33f606c11..41ce18619ffc 100644 > --- a/arch/x86/virt/vmx/tdx/tdx.c > +++ b/arch/x86/virt/vmx/tdx/tdx.c > @@ -1743,16 +1743,23 @@ u64 tdh_vp_addcx(struct tdx_vp *vp, struct page *tdcx_page) > } > EXPORT_SYMBOL_GPL(tdh_vp_addcx); > > -u64 tdh_mem_page_aug(struct tdx_td *td, u64 gpa, int level, struct page *page, u64 *ext_err1, u64 *ext_err2) > +u64 tdh_mem_page_aug(struct tdx_td *td, u64 gpa, int level, struct folio *folio, > + unsigned long start_idx, u64 *ext_err1, u64 *ext_err2) > { > struct tdx_module_args args = { > .rcx = gpa | level, > .rdx = tdx_tdr_pa(td), > - .r8 = page_to_phys(page), > + .r8 = page_to_phys(folio_page(folio, start_idx)), > }; > + unsigned long npages = 1 << (level * PTE_SHIFT); > u64 ret; This 'npages' calculation is not obviously correct. It's not clear what "level" is or what values it should have. This is precisely the kind of place to deploy a helper that explains what is going on. > - tdx_clflush_page(page); > + if (start_idx + npages > folio_nr_pages(folio)) > + return TDX_OPERAND_INVALID; Why is this necessary? Would it be a bug if this happens? > + for (int i = 0; i < npages; i++) > + tdx_clflush_page(folio_page(folio, start_idx + i)); All of the page<->folio conversions are kinda hurting my brain. I think we need to decide what the canonical type for these things is in TDX, do the conversion once, and stick with it.