On Mon, 2024-08-05 at 21:55 -0700, Williams, Dan J wrote: > Kai Huang wrote: > > 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) > > How about check_features()? Almost everything having to do with TDX > concerns the TDX module, so using "module" in a symbol name rarely adds > any useful context. Yeah fine to me. Will do. > > > +{ > > + 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"); > > A user would have no idea with this error message how about something > like: > > pr_err("frame pointer (RBP) clobber bug present, upgrade TDX module\n"); Yeah this is certainly better. Will do. Thanks!
