Old TDX modules can clobber RBP in the TDH.VP.ENTER SEAMCALL. However RBP is used as frame pointer in the x86_64 calling convention, and clobbering RBP could result in bad things like being unable to unwind the stack if any non-maskable exceptions (NMI, #MC etc) happens in that gap. A new "NO_RBP_MOD" feature was introduced to more recent TDX modules to not clobber RBP. This feature is reported in the TDX_FEATURES0 global metadata field via bit 18. Don't initialize the TDX module if this feature is not supported [1]. Link: https://lore.kernel.org/all/c0067319-2653-4cbd-8fee-1ccf21b1e646@xxxxxxxx/T/#mef98469c51e2382ead2c537ea189752360bd2bef [1] Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx> --- arch/x86/virt/vmx/tdx/tdx.c | 17 +++++++++++++++++ arch/x86/virt/vmx/tdx/tdx.h | 1 + 2 files changed, 18 insertions(+) diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c index 88a0c8b788b7..c4ff68b565e8 100644 --- a/arch/x86/virt/vmx/tdx/tdx.c +++ b/arch/x86/virt/vmx/tdx/tdx.c @@ -487,6 +487,18 @@ static int get_tdx_sysinfo(struct tdx_sysinfo *sysinfo) return get_tdx_tdmr_sysinfo(&sysinfo->tdmr_info); } +static int check_module_compatibility(struct tdx_sysinfo *sysinfo) +{ + u64 tdx_features0 = sysinfo->module_info.tdx_features0; + + if (!(tdx_features0 & TDX_FEATURES0_NO_RBP_MOD)) { + pr_err("NO_RBP_MOD feature is not supported\n"); + return -EINVAL; + } + + return 0; +} + /* Calculate the actual TDMR size */ static int tdmr_size_single(u16 max_reserved_per_tdmr) { @@ -1304,6 +1316,11 @@ static int init_tdx_module(void) print_basic_sysinfo(&sysinfo); + /* Check whether the kernel can support this module */ + ret = check_module_compatibility(&sysinfo); + if (ret) + return ret; + /* * To keep things simple, assume that all TDX-protected memory * will come from the page allocator. Make sure all pages in the diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h index be93b6f31e5b..295c3b6d9505 100644 --- a/arch/x86/virt/vmx/tdx/tdx.h +++ b/arch/x86/virt/vmx/tdx/tdx.h @@ -148,6 +148,7 @@ struct tdx_sysinfo_module_info { }; #define TDX_SYS_ATTR_DEBUG_MODULE 0x1 +#define TDX_FEATURES0_NO_RBP_MOD _BITULL(18) /* Class "TDX Module Version" */ struct tdx_sysinfo_module_version { -- 2.43.2
