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Peter Anvin" Subject: Re: [PATCH v5 08/22] x86/virt/seamldr: Allocate and populate a module update request Message-ID: References: <20260315135920.354657-1-chao.gao@intel.com> <20260315135920.354657-9-chao.gao@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260315135920.354657-9-chao.gao@intel.com> On Sun, Mar 15, 2026 at 06:58:28AM -0700, Chao Gao wrote: > P-SEAMLDR uses the SEAMLDR_PARAMS structure to describe TDX module > update requests. This structure contains physical addresses pointing to > the module binary and its signature file (or sigstruct), along with an > update scenario field. > > TDX modules are distributed in the tdx_blob format defined in > blob_structure.txt from the "Intel TDX module Binaries Repository". A > tdx_blob contains a header, sigstruct, and module binary. This is also the > format supplied by the userspace to the kernel. > > Parse the tdx_blob format and populate a SEAMLDR_PARAMS structure > accordingly. This structure will be passed to P-SEAMLDR to initiate the > update. > > Note that the sigstruct_pa field in SEAMLDR_PARAMS has been extended to > a 4-element array. The updated "SEAM Loader (SEAMLDR) Interface > Specification" will be published separately. P-SEAMLDR compatibility > validation (such as 4KB vs 16KB sigstruct support) is left to userspace, > which must verify the P-SEAMLDR version meets the TDX module's minimum > requirements. > > Signed-off-by: Chao Gao > Reviewed-by: Tony Lindgren > Reviewed-by: Xu Yilun > --- > v5: > - use a macro for tdx_blob version (0x100) [Yan] > - don't do alignment checking for the binary/sigstruct [Rick] > - drop blob's sigstruct and validation checking > - set seamldr_params.version to 1 when necessary > - drop the link to blob_structure.txt which might be unstable [Kai] > > v4: > - Remove checksum verification as it is optional > - Convert comments to is_vmalloc_addr() checks [Kai] > - Explain size/alignment checks in alloc_seamldr_params() [Kai] > > v3: > - Print tdx_blob version in hex [Binbin] > - Drop redundant sigstruct alignment check [Yilun] > - Note buffers passed from firmware upload infrastructure are > vmalloc()'d above alloc_seamldr_params() > --- > arch/x86/virt/vmx/tdx/seamldr.c | 141 ++++++++++++++++++++++++++++++++ > 1 file changed, 141 insertions(+) > > diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c > index 7114326d7569..20cb6c797ce5 100644 > --- a/arch/x86/virt/vmx/tdx/seamldr.c > +++ b/arch/x86/virt/vmx/tdx/seamldr.c > @@ -7,6 +7,7 @@ > #define pr_fmt(fmt) "seamldr: " fmt > > #include > +#include > #include > > #include > @@ -16,6 +17,33 @@ > /* P-SEAMLDR SEAMCALL leaf function */ > #define P_SEAMLDR_INFO 0x8000000000000000 > > +#define SEAMLDR_MAX_NR_MODULE_4KB_PAGES 496 > +#define SEAMLDR_MAX_NR_SIG_4KB_PAGES 4 > + > +/* > + * The seamldr_params "scenario" field specifies the operation mode: > + * 0: Install TDX module from scratch (not used by kernel) > + * 1: Update existing TDX module to a compatible version > + */ > +#define SEAMLDR_SCENARIO_UPDATE 1 > + > +/* > + * This is called the "SEAMLDR_PARAMS" data structure and is defined > + * in "SEAM Loader (SEAMLDR) Interface Specification". > + * > + * It describes the TDX module that will be installed. > + */ > +struct seamldr_params { > + u32 version; > + u32 scenario; > + u64 sigstruct_pa[SEAMLDR_MAX_NR_SIG_4KB_PAGES]; > + u8 reserved[80]; > + u64 num_module_pages; > + u64 mod_pages_pa_list[SEAMLDR_MAX_NR_MODULE_4KB_PAGES]; > +} __packed; > + > +static_assert(sizeof(struct seamldr_params) == 4096); > + > /* > * Serialize P-SEAMLDR calls since the hardware only allows a single CPU to > * interact with P-SEAMLDR simultaneously. Use raw version as the calls can > @@ -41,6 +69,114 @@ int seamldr_get_info(struct seamldr_info *seamldr_info) > } > EXPORT_SYMBOL_FOR_MODULES(seamldr_get_info, "tdx-host"); > > +static void free_seamldr_params(struct seamldr_params *params) > +{ > + free_page((unsigned long)params); > +} > + > +static struct seamldr_params *alloc_seamldr_params(const void *module, unsigned int module_size, > + const void *sig, unsigned int sig_size) > +{ > + struct seamldr_params *params; > + const u8 *ptr; > + int i; > + > + if (module_size > SEAMLDR_MAX_NR_MODULE_4KB_PAGES * SZ_4K) > + return ERR_PTR(-EINVAL); > + > + if (sig_size > SEAMLDR_MAX_NR_SIG_4KB_PAGES * SZ_4K) > + return ERR_PTR(-EINVAL); > + > + params = (struct seamldr_params *)get_zeroed_page(GFP_KERNEL); > + if (!params) > + return ERR_PTR(-ENOMEM); > + > + /* > + * Only use version 1 when required (sigstruct > 4KB) for backward > + * compatibility with P-SEAMLDR that lacks version 1 support. > + */ > + if (sig_size > SZ_4K) > + params->version = 1; > + else > + params->version = 0; > + > + params->scenario = SEAMLDR_SCENARIO_UPDATE; > + > + ptr = sig; > + for (i = 0; i < sig_size / SZ_4K; i++) { > + /* > + * Don't assume @sig is page-aligned although it is 4KB-aligned. > + * Always add the in-page offset to get the physical address. > + */ I don't follow this. If @sig is 4k aligned in VA, it is page aligned. If you want to handle case when @sig is not 4k aligned, than this is broken. You need to bump ptr to the next 4k boundary, not by 4k. > + params->sigstruct_pa[i] = (vmalloc_to_pfn(ptr) << PAGE_SHIFT) + > + ((unsigned long)ptr & ~PAGE_MASK); > + ptr += SZ_4K; > + } > + > + params->num_module_pages = module_size / SZ_4K; > + > + ptr = module; > + for (i = 0; i < params->num_module_pages; i++) { > + params->mod_pages_pa_list[i] = (vmalloc_to_pfn(ptr) << PAGE_SHIFT) + > + ((unsigned long)ptr & ~PAGE_MASK); > + ptr += SZ_4K; Same here. > + } > + > + return params; > +} > + > +/* > + * Intel TDX module blob. Its format is defined at: > + * https://github.com/intel/tdx-module-binaries/blob/main/blob_structure.txt > + * > + * Note this structure differs from the reference above: the two variable-length > + * fields "@sigstruct" and "@module" are represented as a single "@data" field > + * here and split programmatically using the offset_of_module value. > + */ > +struct tdx_blob { > + u16 version; > + u16 checksum; > + u32 offset_of_module; > + u8 signature[8]; > + u32 length; > + u32 reserved0; > + u64 reserved1[509]; > + u8 data[]; > +} __packed; > + > +/* Supported versions of the tdx_blob */ > +#define TDX_BLOB_VERSION_1 0x100 > + > +static struct seamldr_params *init_seamldr_params(const u8 *data, u32 size) > +{ > + const struct tdx_blob *blob = (const void *)data; > + int module_size, sig_size; > + const void *sig, *module; > + > + /* Ensure the size is valid otherwise reading any field from the blob may overflow. */ > + if (size <= sizeof(struct tdx_blob) || size <= blob->offset_of_module) > + return ERR_PTR(-EINVAL); > + > + if (blob->version != TDX_BLOB_VERSION_1) { > + pr_err("unsupported blob version: %x\n", blob->version); > + return ERR_PTR(-EINVAL); > + } > + > + /* Split the blob into a sigstruct and a module. */ > + sig = blob->data; > + sig_size = blob->offset_of_module - sizeof(struct tdx_blob); > + module = data + blob->offset_of_module; > + module_size = size - blob->offset_of_module; > + > + if (sig_size <= 0 || module_size <= 0 || blob->length != size) > + return ERR_PTR(-EINVAL); Maybe add a comment somewhere that block->offset_of_module is relative to start of struct tdx_blob, not blob->data and blob->length includes length of struct tdx_blob. It can be either way and it is better to give a reader a hint. > + > + return alloc_seamldr_params(module, module_size, sig, sig_size); > +} > + > +DEFINE_FREE(free_seamldr_params, struct seamldr_params *, > + if (!IS_ERR_OR_NULL(_T)) free_seamldr_params(_T)) > + > /** > * seamldr_install_module - Install a new TDX module. > * @data: Pointer to the TDX module update blob. > @@ -50,6 +186,11 @@ EXPORT_SYMBOL_FOR_MODULES(seamldr_get_info, "tdx-host"); > */ > int seamldr_install_module(const u8 *data, u32 size) > { > + struct seamldr_params *params __free(free_seamldr_params) = > + init_seamldr_params(data, size); > + if (IS_ERR(params)) > + return PTR_ERR(params); > + > /* TODO: Update TDX module here */ > return 0; > } > -- > 2.47.3 > -- Kiryl Shutsemau / Kirill A. Shutemov