[PATCH v2 10/10] x86/virt/tdx: Don't initialize module that doesn't support NO_RBP_MOD feature
From: Kai Huang
Date: Tue Jul 16 2024 - 23:43:38 EST
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>
Reviewed-by: Nikolay Borisov <nik.borisov@xxxxxxxx>
---
v1 -> v2:
- Add tag from Nikolay.
---
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 3c19295f1f8f..ec6156728423 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -484,6 +484,18 @@ 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)
{
@@ -1266,6 +1278,11 @@ 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 4b43eb774ffa..20fd7cb5937a 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 {
--
2.45.2