x86/virt/tdx: Don't initialize module that doesn't support NO_RBP_MOD…

… feature 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/[email protected]/T/#mef98469c51e2382ead2c537ea189752360bd2bef [1] Signed-off-by: Kai Huang <[email protected]>
intel · Jun 25, 2024 · be294be · be294be
1 parent 7da0bea
commit be294be
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Showing 2 changed files with 18 additions and 0 deletions.
diff --git 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
@@ -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 {